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About ImageMagick
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Below is list of command-line options recognized by the ImageMagick command-line tools. If you want a description of a particular option, click on the option name in the navigation bar above and you will go right to it. adaptively blur pixels; descreasing its effect near edges. Use a Gaussian operator of the given radius and standard deviation (sigma). resize image with data dependent triangulation. See -resize for details about the geometry specification. The -adaptive-resize option defaults to data dependent triangulation. Use the -filter to choose a different resampling algorithm. Offsets, if present in the geometry string, are ignored, and the -gravity option has no effect. adaptively sharpen pixels; increasng its effect near edges. Use a Gaussian operator of the given radius and standard deviation (sigma). join images into a single multi-image file. Enabled by default. -adjoin will try to save all images of an image sequence in the same file. However, some formats (e.g. JPEG) do not support more than one image and are saved to separate files. Use +adjoin to force this behavior for all image format. Set the drawing transformation matrix. This option provides a transformation matrix {sx, rx, ry, sy, tx, ty} for use by subsequent -draw or -transform options. The transformation matrix has 3x3 elements, but three of them are omitted from the input because they are constant. The new coordinate { x', y' } of a pixel {x, y} in the transformed image is calculated using the following matrix equation:
| sx rx 0 |
{ x' y' 1 } = { x y 1 } * | ry sy 0 |
| tx ty 1 |
The size of the resulting image is set so that the rotated and scaled source image is exactly contained within the new image area. The tx and ty parameters subsequently shift the image pixels so that those that are moved out of the image area are cut off. As do the pixel coordinates, the transform matrix uses a left-handed coordinate system (positive direction is rightward resp. downward; positive rotation is clockwise). Scaling by the factor s is accomplished with the matrix:
{s, 0, 0, s, 0, 0}
Translation by a displacement {dx, dy} is accomplished with the matrix:
{1, 0, 0, 1, dx, dy}
Rotation clockwise about the origin by an angle a is accomplished with the matrix:
{cos(a), sin(a), -sin(a), cos(a), 0, 0}
A series of operations can be accomplished by using a matrix that is the multiple of the matrices for each operation. control and special operations of the alpha/matte channel of an image Alpha sets a flag on an image indicating whether or not to use alpha channel data. Choose from these options: on off reset set on/off will activate/deactivate the use of an images alpha channel data. Reset sets the alpha channel to fully opaque. Set copies the gray-scale intensity of the image into the alpha channel, converting a gray-scale mask, into a transparent shaped image ready to be colored appropriately. The -matte operation is equivelent to doing a "-alpha on", followed by a "-alpha reset" if the image did not have a matte/alpha channel before hand. The +matte operation is however exactly the same as a "-alpha off", the alpha channel is left in place, just disabled. annotate an image with text. This is a convenience option for annotating your image with text. For more precise control over your text annotations, use -draw. X-rotate and Y-rotate give the angle of the text and x and y are offsets that give the location of the text relative to the upper left corner of the image. If the first character of text is @, the text is read from a file titled by the remaining characters in the string. Text in a file are literal, no embedded formatting characters are recognized. remove pixel aliasing. By default, objects are antialiased when drawn (e.g. lines, polygon, etc.). Use +antialias to disable antialiasing. Without antialiasing, you can avoid increasing the unique colors in an image, draw fixed width lines, or improve the rendering speed. append a set of images. This option creates a single image where the images in the original set are stacked top-to-bottom. If they are not of the same width, any narrow images will be expanded to fit using the current -background color setting. Use +append to stack images left-to-right. The set of images is terminated by the appearance of any option. If the -append option appears after all of the input images, all images are appended. lessen (or intensify) when adding noise to an image. decipher image with this password. Use this option to supply a password for decipher an image or an image sequence, if it is being read from a format such as PDF that supports enciphering. Enciphering images being written is not supported. automatically orient (rotate) image from a digital camera. average a set of images. The set of images is terminated by the appearance of any option. If the -average option appears after all of the input images, all images are averaged. display the image centered on a backdrop. This backdrop covers the entire workstation screen and is useful for hiding other X window activity while viewing the image. The color of the backdrop is specified as the background color. The color is specified using the format described under the -fill option. the background color. The color is specified using the format described under the -fill option. add bias when convolving an image. use black point compensation. force all pixels at or below the threshold into black while leaving all pixels above the threshold unchanged. blue chromaticity primary point. reduce image noise and reduce detail levels. Convolve the image with a Gaussian or normal distribution. The formula is: where r is the blur radius (r2 = u2 + v2), and σ is the standard deviation of the Gaussian distribution. As a guideline, set r to approximately 3σ. Specify a radius of 0 and ImageMagick selects a suitable radius for you. This option differs from -gaussian-blur simply by taking advantage of the linear separable properties of the distribution. Here we apply a single-dimensional Gaussian matrix in the horizontal direction, then repeat the process in the vertical direction. surround the image with a border of color. See -resize for details about the geometry specification. the border color. The color is specified using the format described under the -fill option. the border width. (This option has been replaced by the -limit option). assign a caption to an image. define the image color channels later operators may be limited to. Choose from: Red, Green, Blue, Alpha, Cyan, Magenta, Yellow, Black, Opacity, Index, RGB, RGBA, CMYK, or CMYKA. To print a complete list of channel types, use the -list channel option. You can specify the above as a comma separated list of channels, or concatenate the letters 'R', 'G', 'B', 'A', 'O', 'C', 'M', 'Y', 'K', to specify specific multiple channels for later operators to be applied to. For example to only negate the alpha channel of an image, use
-channel Alpha -negate
By default, ImageMagick sets "-channel to the value 'RGB' to limit channel affected operators to all channels, except the opacity channel, in an image. Using the option "+channel will reset the value back to this default. Operators that are affected by the "-channel setting include: "-blur, "-combine, "-contrast-stretch, "-evaluate, "-fx, "-gaussian-blur, "-motion-blur, "-negate, "-normalize, "-ordered-dither, "-radial-blur, "-random-threshold, "-separate, and -threshold. simulate a charcoal drawing. remove pixels from the interior of an image. Width and height give the number of columns and rows to remove, and x and y are offsets that give the location of the leftmost column and topmost row to remove. The x offset normally specifies the leftmost column to remove. If the -gravity option is present with NorthEast, East, or SouthEast gravity, it gives the distance leftward from the right edge of the image to the rightmost column to remove. Similarly, the y offset normally specifies the topmost row to remove, but if the -gravity option is present with SouthWest, South, or SouthEast gravity, it specifies the distance upward from the bottom edge of the image to the bottom row to remove. The -chopoption removes entire rows and columns, and moves the remaining corner blocks leftward and upward to close the gaps. apply the clipping path, if one is present. If a clipping path is present, it will be applied to subsequent operations. For example, if you type the following command:
convert -clip -negate cockatoo.tif negated.tif
only the pixels within the clipping path are negated. The -clip feature requires the XML library. If the XML library is not present, the option is ignored. clip image as defined by this mask. clip along a named path from the 8BImageMagick profile. make a copy of an image (or images). Specify the image by its index in the sequence. The first image is index 0. Negative indexes are relative to the end of the sequence, for example, -1 represents the last image of the sequence. Specify a range of images with a dash (e.g. 0-4). Separate indexes with a comma (e.g. 0,2). Use +clone make a copy of the last image in the image sequence. Given two images, replace the channel values in the first image, with a lookup of its replacement value in second LUT gradient image. The LUT image should be either a single row or column image of replacement colors. The lookup is controled by the -interpolate setting, especially for an LUT which is not the full length needed by the ImageMagick installed Quailty (Q) level. Good setings for this is the default 'bilinear' or 'bicubic' interpolation setting for a smooth color gradient, or 'integer' for a direct unsmoothed lookup of color values. Also only the channel values defined by the -channel setting will have there values replaced. This operator is especially suited to replacing a grayscale image with specific color gradient from the CLUT image. Note that color replacements involving transparency (alpha/matte channel) will lookup the replacement alpha/matte value using the alpha/matte value of the original image. As such correct alpha channel lookup for a pure gray-scale original image will require a copy of that grayscale to be transfered into its alpha channel before applying the -clut operator. The special "-alpha set" operation can be used for this purpose. Fully define the look of each frame of an GIF animation sequence, to form a 'film strip' like animation. Overlay each image in an image sequence accoding to their -dispose meta-data, to re-produce the actual look of an animation at each point in the animation sequence. All images the same size, and are assigned appropriate GIF disposal settings so the animation will continues to work as expected as a GIF animation. Such frames are more easilly viewed, and processed, than the highly optimized GIF overlay images. The animation can be re-optimized after processing using the -layers method 'optimize', though there is no gurantee that the restored GIF animation optimization will be better than the original. colorize the image with the fill color. Specify the amount of colorization as a percentage. You can apply separate colorization values to the red, green, and blue channels of the image with a colorization value list delimited with commas (e.g. 0,0,50). define the colormap type. Choose between shared or private. This option only applies when the default X server visual is PseudoColor or GrayScale. Refer to -visual for more details. By default, a shared colormap is allocated. The image shares colors with other X clients. Some image colors could be approximated, therefore your image may look very different than intended. Choose Private and the image colors appear exactly as they are defined. However, other clients may go technicolor when the image colormap is installed. preferred number of colors in the image. The actual number of colors in the image may be less than your request, but never more. Note, this is a color reduction option. Images with less unique colors than specified with this option will have any duplicate or unused colors removed. The ordering of an existing color palette may be altered. When converting an image from color to grayscale, convert the image to the gray colorspace before reducing the number of colors since doing so is most efficient. Refer to the color reduction algorithm for more details. the image colorspace. Choices are: CMY CMYK Gray HSB HSL HWB Lab Log OHTA Rec601Luma Rec601YCbCr Rec709Luma Rec709YCbCr RGB sRGB Transparent XYZ YCbCr YCC YIQ YPbPr YUV To print a complete list of colorspaces, use the -list colorspace option. For a more accurate color conversion to or from the RGB, CMYK, or grayscale colorspaces use the -profile option.
combine one or more images into a single image. The grayscale value of the pixels of each image in the sequence is assigned in order to the specified channels of the combined image. The typical ordering would be image 1 = Red, 2 = Green, 3 = Blue, etc. annotate an image with a comment. Use this option to assign a specific comment to the image, when writing to an image format that supports comments. You can include the image filename, type, width, height, or other image attribute by embedding special format characters listed under the -format option. The comment is not drawn on the image, but is embedded in the image datastream via a "Comment" tag or similar mechanism. If you want the comment to be visible on the image itself, use the -draw option. For example,
-comment "%m:%f %wx%h"
produces an image comment of MIFF:bird.miff 512x480 for an image titled bird.miff and whose width is 512 and height is 480. If the first character of string is @, the image comment is read from a file titled by the remaining characters in the string. Comments in a file are literal, no embedded formatting characters are recognized. the type of image composition. The description of composition uses abstract terminology in order to allow the description to be more clear, while avoiding constant values which are specific to a particular build configuration. Each image pixel is represented by red, green, and blue levels (which are equal for a gray pixel). QuantumRange is the maximum integral value which may be stored in the red, green, or blue channels of the image. Each image pixel may also optionally (if the image matte channel is enabled) have an associated level of opacity (ranging from opaque to transparent), which may be used to determine the influence of the pixel color when compositing the pixel with another image pixel. If the image matte channel is disabled, then all pixels in the image are treated as opaque. The color of an opaque pixel is fully visible while the color of a transparent pixel color is entirely absent (pixel color is ignored). By definition, raster images have a rectangular shape. All image rows are of equal length, and all image columns have the same number of rows. By treating the alpha channel as a visual "mask" the rectangular image may be given a "shape" by treating the alpha channel as a cookie-cutter for the image. Pixels within the shape are opaque, while pixels outside the shape are transparent. Pixels on the boundary of the shape may be between opaque and transparent in order to provide antialiasing (visually smooth edges). The description of the composition operators use this concept of image "shape" in order to make the description of the operators easier to understand. While it is convenient to describe the operators in terms of "shapes" they are by no means limited to mask-style operations since they are based on continuous floating-point mathematics rather than simple boolean operations. The following composite methods are available:
To print a complete list of composite operators, use the -list composite option. There can be more methods listed, that what is shown above, many of these require special arguments, restricting there use to special composition operators, such as -blend, -dissolve, and -displace. perform alpha composition on the current image sequence. This is done according to the current -compose setting with the source image offset but the position given by -geometry use this type of pixel compression when writing the image. Choices are: None, BZip, Fax, Group4, JPEG, JPEG2000, Lossless, LZW, RLE or Zip. To print a complete list of compression types, use the -list compress option. Specify +compress to store the binary image in an uncompressed format. The default is the compression type of the specified image file. If LZW compression is specified but LZW compression has not been enabled, the image data will be written in an uncompressed LZW format that can be read by LZW decoders. This may result in larger-than-expected GIF files. Lossless refers to lossless JPEG, which is only available if the JPEG library has been patched to support it. Use of lossless JPEG is generally not recommended. Use the -quality option to set the compression level to be used by JPEG, PNG, MIFF, and MPEG encoders. Use the -sampling-factor option to set the sampling factor to be used by JPEG, MPEG, and YUV encoders for down-sampling the chroma channels. enhance or reduce the image contrast. This option enhances the intensity differences between the lighter and darker elements of the image. Use -contrast to enhance the image or +contrast to reduce the image contrast. For a more pronounced effect you can repeat the option:
convert rose: -contrast -contrast rose_c2.png
Increase the contrast in an image by stretching the range of intensity values. While doing so black-out at most black-point pixels and white-out at most white-point pixels. Or, if percent is used, black-out at most black-point % pixels and white-out at most 100% minus white-point% pixels. Note that -contrast-stretch 0 will modify the image such that the image's min and max values are stretched to 0 and QuantumRange, respectively, without any loss of data due to burn-out at either end. This is not the same as -normalize, which is equivalent to -contrast-stretch 2%,99%. The channels are stretched in concert. Specify -channel to normalize the RGB channels individually. convolve image with the specified convolution kernel. The kernel is specified as a comma-separated list of integers, ordered left-to right, starting with the top row. The order of the kernel is determined by the square root of the number of entries. Presently only square kernels are supported. cut out a rectangular region of the image. See -resize for details about the geometry specification. The width and height give the size of the image that remains after cropping, and x and y are offsets that give the location of the top left corner of the cropped image with respect to the original image. To specify the amount to be removed, use -shave instead. If the x and y offsets are present, a single image is generated, consisting of the pixels from the cropping region. The offsets specify the location of the upper left corner of the cropping region measured downward and rightward with respect to the upper left corner of the image. If the -gravity option is present with NorthEast, East, or SouthEast gravity, it gives the distance leftward from the right edge of the image to the right edge of the cropping region. Similarly, if the -gravity option is present with SouthWest, South, or SouthEast gravity, the distance is measured upward between the bottom edges. If the x and y offsets are omitted, a set of tiles of the specified geometry, covering the entire input image, is generated. The rightmost tiles and the bottom tiles are smaller if the specified geometry extends beyond the dimensions of the input image. By adding a exclamation character flag to the geometry argument, the cropped images virtual canvas page size and offset will be set as if the geometry argument was a viewport or window. This means the canvas page size will be set to exactly the same size you specified, the the image offset set relative to top left corner of the region cropped. If the cropped image 'missed' the actual image on its virtual canvas, a special single pixel transparent 'missed' image is returned, and a 'crop missed' warning given. displace image colormap by amount. Amount defines the number of positions each colormap entry is shifted. convert cipher pixels to plain pixels. Get the passphrase from the specified filename. enable debug printout. The events parameter specifies which events are to be logged. It can be either None, All, Trace, or a comma-separated list consisting of one or more of the following domains: Annotate, Blob, Cache, Coder, Configure, Deprecate, Exception, Locale, Render, Resource, TemporaryFile, Transform, X11, or User. For example, to log cache and blob events, use.
convert -debug "Cache,Blob" rose: rose.png
The User domain is normally empty, but developers can log user events in their private copy of ImageMagick. Use the -log option to specify the format for debugging output. Use +debug to turn off all logging. Debugging may also be set using the MAGICK_DEBUG environment variable. The allowed values for the MAGICK_DEBUG environment variable are the same as for the -debug option. find areas that has changed between images Given a sequence of images all the same size, such as produced by -coalesce, replace the second and later images, with a smaller image of just the area that changed relative to the previous image. The resulting sequence of images can be used to optimize an animation sequence, though will not work correctly for GIF animations when parts of the animation can go from opaque to transparent. This option is actually equivalent to the -layers method 'compare-any'. add coder/decoder specific options. This option creates one or more definitions for coders and decoders to use while reading and writing image data. Definitions may be passed to coders and decoders to control options that are specific to certain image formats. If value is missing for a definition, an empty-valued definition of a flag will be created with that name. This is used to control on/off options. Use +define key to remove definitions previously created. Use +define "*" to remove all existing definitions. The following definitions may be created:
jp2:rate=value
Specify the compression factor to use while writing JPEG-2000
files. The compression factor is the reciprocal of the compression
ratio. The valid range is 0.0 to 1.0, with 1.0 indicating lossless
compression. If defined, this value overrides the -quality setting.
A quality setting of 75 results in a rate value of 0.06641.
mng:need-cacheoff
turn playback caching off for streaming MNG.
ps:imagemask
If the ps:imagemask flag is defined, the PS3 and EPS3 coders will
create Postscript files that render bilevel images with the Postscript
imagemask operator instead of the image operator.
For example, to create a postscript file that will render only the black pixels of a bilevel image, use:
convert bilevel.tif -define ps:imagemask eps3:stencil.ps
Set attributes of the image registry by prefixing the value with registry:. For example, to set a temporary path to put work files, use: convert -define registry:temporary-path=/data/tmp ... display the next image after pausing. This option is useful for regulating the animation of image sequences ticks/ticks-per-second seconds must expire before the display of the next image. The default is no delay between each showing of the image sequence. The default ticks-per-second is 100. Use > to change the image delay only if its current value exceeds the given delay. < changes the image delay only if current value is less than the given delay. For example, if you specify 30> and the image delay is 20, the image delay does not change. However, if the image delay is 40 or 50, the delay it is changed to 30. Enclose the given delay in quotation marks to prevent the < or > from being interpreted by your shell as a file redirection. delete the image, specified by its index, from the image sequence. Specify the image by its index in the sequence. The first image is index 0. Negative indexes are relative to the end of the sequence, for example, -1 represents the last image of the sequence. Specify a range of images with a dash (e.g. 0-4). Separate indexes with a comma (e.g. 0,2). Use +delete to delete the last image in the current image sequence. horizontal and vertical resolution in pixels of the image. This option specifies the image resolution to store while encoding a raster image or the canvas resolution while rendering (reading) vector formats such as Postscript, PDF, WMF, and SVG into a raster image. Image resolution provides the unit of measure to apply when rendering to an output device or raster image. The default unit of measure is in dots per inch (DPI). The -units option may be used to select dots per centimeter instead. The default resolution is 72 dots per inch, which is equivalent to one point per pixel (Macintosh and Postscript standard). Computer screens are normally 72 or 96 dots per inch while printers typically support 150, 300, 600, or 1200 dots per inch. To determine the resolution of your display, use a ruler to measure the width of your screen in inches, and divide by the number of horizontal pixels (1024 on a 1024x768 display). If the file format supports it, this option may be used to update the stored image resolution. Note that Photoshop stores and obtains image resolution from a proprietary embedded profile. If this profile is not stripped from the image, then Photoshop will continue to treat the image using its former resolution, ignoring the image resolution specified in the standard file header. The density option is an attribute and does not alter the underlying raster image. It may be used to adjust the rendered size for desktop publishing purposes by adjusting the scale applied to the pixels. To resize the image so that it is the same size at a different resolution, use the -resample option. depth of the image. This is the number of bits in a color sample within a pixel. Use this option to specify the depth of raw images whose depth is unknown such as GRAY, RGB, or CMYK, or to change the depth of any image after it has been read. obtain image by descending window hierarchy. straighten an image. A threshold of 40% works for most images. Use -set 'option:deskew:auto-crop width' option to auto crop the image. The set argument is the pixel width of the image background (e.g 40). reduce the speckles within an image. shift image pixels as defined by a displacement map. With this option, composite image is used as a displacement map. Black, within the displacement map, is a maximum positive displacement. White is a maximum negative displacement and middle gray is neutral. The displacement is scaled to determine the pixel shift. By default, the displacement applies in both the horizontal and vertical directions. However, if you specify mask, composite image is the horizontal X displacement and mask the vertical Y displacement. specifies the X server to contact. This option is used with convert for obtaining image or font from this X server. See X(1). define the GIF disposal image setting for images that are being created or read in. The layer disposal method defines the way each the displayed image is to be modified after the current 'frame' of an animation has finished being displayed (after its 'delay' period), but before the next frame on an animation is to be overlaid onto the display. Here are the valid methods: Undefined 0 No disposal specified (equivalent to 'none'). None 1 Do not dispose, just overlay next frame image. Background 2 Clear the frame area with the background color. Previous 3 Clear to the image prior to this frames overlay. You can also use the numbers given above, which is what the GIF format uses internally to represent the above settings.
To print a complete list of dispose methods, use the -list dipose option. Use +dispose, turn off the setting and prevent resetting the layer disposal methods of images being read in. Use -set 'dispose' method to set the image disposal method for images already in memory. dissolve an image into another by the given percent. The opacity of the composite image is multiplied by the given percent, then it is composited over the main image. distort an image, using the given method and its required arguments. The arguments is a single string containing a list of floating point numbers separated by commas or spaces. The number of floating point values need depends on the distortion method being used. Choose from these distortion types:
To print a complete list of distortion methods, use the -list distort option. Many of the above methods are based on how a set of individual coordinates should be translated when image is distorted. Such a coordinate list is given as a sequence of pairs of coordinates, source X,Y coordinate, followed immediataly by that points distorted X,Y coordinate (4 floating point values). For example, to warp an image using 'perspective' distortion, you need a list of at least 4 coordinate pairs, or 16 numbers. These number could be thought of as representing the distortion of a quadraterial from the source image to the distorted image. Here is the perspective distortion of the built-in "rose:" image. Note the 4 sets of coordinate pairs.
convert rose: -virtual-pixel black \
-distort Perspective '0,0,0,0 0,45,0,45 69,0,60,10 69,45,60,35' \
rose_3d_rotated.gif
If more that the minimum number of coordinate pairs are given, then the distortion method will be 'least squares' fitted to produce the best result for all the coordinate pairs given. It also allows the use of image registration to find coordinate pairs. Using extra coordinate pairs can be used to improve the fit of a distorted image to another image or chart beyond the resolution of a pixel coordinate. Of course a bad coordinate pair can also make the 'fit' worse. Caution is always advised. The output image size will by default be the same as the input image. This means that if the part of the distorted image falls outside the viewed areas of the 'distorted space', those parts will be clipped and lost. However if you use the plus form of the operator (+distort) the resulting image will be automatically adjusted to show the whole of the distorted image, using the smallest image possible, if it is posible for that distortion method. A 'virtual canvas' offset will also then be added to the resulting image to locate that image in 'distorted space'. Use a +repage, to remove this offset if it is unwanted. You can alternatively specify a special "-set option:distort:viewport {geometry_string}" setting which will specify the size and the offset of the generated 'viewport' image of the distorted image space. Colors are acquired from the source image according to the -interpolate color lookup setting, when the image is magnified. However if the viewed image is minified (image becomes smaller), a special area resampling function (added ImageMagick v6.3.5-9), is used to produce a higher quality image. For example you can use a 'perspective' distortion to view a infinitely tiled 'plane' all the way to the horizon. For example...
convert -size 90x90 pattern:checkerboard -normalize -virtual-pixel tile \
-distort perspective '0,0,5,45 89,0,45,46 0,89,0,89 89,89,89,89' \
checks_tiled.jpg
Warning, infinitely tiled perspective images involving the horizon can be very slow to generate due to the use of the high quality 'area resampling' function (added ImageMagick v6.3.5-9). You can turn off 'area resampling' using a -filter setting of 'point', but the quality will suffer badly. If an image generates invalid pixels, such as the 'sky' in the last 'perspective' distortion example, -distort will use the current -mattecolor setting for these pixels. If you do not what this 'sky' to be visible, set the color to match the rest of the ground. Affine rotations and shears (such as 'SRT' distortion), tend to produce a cleaner result that the equivalent -rotate and/or -shear operation, with more control of due to the above settings. It is algorithmically slower, though in IM it may be faster. Apply a Hilbert-Peano error diffusion dither to images when general color reduction is applied via an option, or automatically when saving to specific formats. This is enabled by default. Dithering places two or more colors in neighbouring pixels so that to the eye a closer approximation of the images original color is reproduced. This reduces the number of colors needed to reproduce the image but at the cost of a lower level pattern of colors. Error diffusion dithers can use any set of colors (generated or user defined) to an image. Use +dither to turn off dithering (the default), and to also render PostScript without text or graphic aliasing. Disabling dithering often (but not always) leads to faster process, a smaller number of colors, but more cartoon like image coloring. Generally resulting in 'color banding' effects in areas with color gradients. The color reduction operators -colors, -monochrome, -map, and -posterize, apply dithering to images using the reduced color set they created. These operators are also used as part of automatic color reduction when saving images to formats with limited color support, such as GIF:, XBM:, and others, so dithering may also be used in these cases. Alternativelly you can use -random-threshold to generate purely random dither. Or use -ordered-dither to apply threshold mapped dither patterns, using uniform color maps, rather than specific color maps. annotate an image with one or more graphic primitives. Use this option to annotate an image with one or more graphic primitives. The primitives include shapes, text, transformations, and pixel operations. The shape primitives are: point x,y line x0,y0 x1,y1 rectangle x0,y0 x1,y1 roundRectangle x0,y0 x1,y1 wc,hc arc x0,y0 x1,y1 a0,a1 ellipse x0,y0 rx,ry a0,a1 circle x0,y0 x1,y1 polyline x0,y0 ... xn,yn polygon x0,y0 ... xn,yn Bezier x0,y0 ... xn,yn path path specification image operator x0,y0 w,h filename The text primitive is. text x0,y0 string The text gravity primitive is.
gravity NorthWest, North, NorthEast, West, Center,
East, SouthWest, South, or SouthEast
The text gravity primitive only affects the placement of text and does not interact with the other primitives. It is equivalent to using the -gravity commandline option, except that it is limited in scope to the -draw option in which it appears. The transformation primitives are. rotate degrees translate dx,dy scale sx,sy skewX degrees skewY degrees The pixel operation primitives are. color x0,y0 method matte x0,y0 method The shape primitives are drawn in the color specified in the preceding -fill option. For unfilled shapes, use -fill none. You can optionally control the stroke with the -stroke and -strokewidth options. Point requires a single coordinate. Line requires a start and end coordinate. Rectangle expects an upper left and lower right coordinate. RoundRectangle has the upper left and lower right coordinates and the width and height of the corners. Circle has a center coordinate and a coordinate for the outer edge. Use Arc to inscribe an elliptical arc within a rectangle. Arcs require a start and end point as well as the degree of rotation (e.g. 130,30 200,100 45,90). Use Ellipse to draw a partial ellipse centered at the given point with the x-axis and y-axis radius and start and end of arc in degrees (e.g. 100,100 100,150 0,360). Finally, polyline and polygon require three or more coordinates to define its boundaries. Coordinates are integers separated by an optional comma. For example, to define a circle centered at 100,100 that extends to 150,150 use: -draw 'circle 100,100 150,150' Paths (See Paths) represent an outline of an object which is defined in terms of moveto (set a new current point), lineto (draw a straight line), curveto (draw a curve using a cubic Bezier), arc (elliptical or circular arc) and closepath (close the current shape by drawing a line to the last moveto) elements. Compound paths (i.e., a path with subpaths, each consisting of a single moveto followed by one or more line or curve operations) are possible to allow effects such as donut holes in objects. Use image to composite an image with another image. Follow the image keyword with the composite operator, image location, image size, and filename: -draw 'image Over 100,100 225,225 image.jpg' You can use 0,0 for the image size, which means to use the actual dimensions found in the image header. Otherwise, it will be scaled to the given dimensions. See -compose for a description of the composite operators. Use text to annotate an image with text. Follow the text coordinates with a string. If the string has embedded spaces, enclose it in single or double quotes. For example, -draw 'text 100,100 "Works like magick!"' annotates the image with Works like magick! for an image titled bird.miff. See the -annotate option for another convenient way to annotate an image with text. Rotate rotates subsequent shape primitives and text primitives about the origin of the main image. If the -region option precedes the -draw option, the origin for transformations is the upper left corner of the region. Translate translates them. Scale scales them. SkewX and SkewY skew them with respect to the origin of the main image or the region. The transformations modify the current affine matrix, which is initialized from the initial affine matrix defined by the -affine option. Transformations are cumulative within the -draw option. The initial affine matrix is not affected; that matrix is only changed by the appearance of another -affineoption. If another -draw option appears, the current affine matrix is reinitialized from the initial affine matrix. Use color to change the color of a pixel to the fill color (see -fill). Follow the pixel coordinate with a method: point replace floodfill filltoborder reset Consider the target pixel as that specified by your coordinate. The point method recolors the target pixel. The replace method recolors any pixel that matches the color of the target pixel. Floodfill recolors any pixel that matches the color of the target pixel and is a neighbor, whereas filltoborder recolors any neighbor pixel that is not the border color. Finally, reset recolors all pixels. Use matte to the change the pixel matte value to transparent. Follow the pixel coordinate with a method (see the color primitive for a description of methods). The point method changes the matte value of the target pixel. The replace method changes the matte value of any pixel that matches the color of the target pixel. Floodfill changes the matte value of any pixel that matches the color of the target pixel and is a neighbor, whereas filltoborder changes the matte value of any neighbor pixel that is not the border color (-bordercolor). Finally reset changes the matte value of all pixels. You can set the primitive color, font, and font bounding box color with -fill, -font, and -box respectively. Options are processed in command line order so be sure to use these options before the -draw option. Drawing primitives conform to the Magick Vector Graphics format. detect edges within an image. emboss an image. convert plain pixels to cipher pixels. Get the passphrase from the specified filename. specify the text encoding. Choose from AdobeCustom, AdobeExpert, AdobeStandard, AppleRoman, BIG5, GB2312, Latin 2, None, SJIScode, Symbol, Unicode, Wansung. specify endianness (MSB or LSB) of the image. To print a complete list of endian type, use the -list endian option. Use +endian to revert to unspecified endianness. apply a digital filter to enhance a noisy image. perform histogram equalization on the image channel-by-channel. To perform histogram equalization on all channels in concert, transform the image into some other color space, such as HSL, OHTA, YIQ or YUV, then equalize the appropriate intensity-like channel, then convert back to RGB. For example using HSL, we have: ... -colorspace HSL -channel lightness -equalize -colorspace RGB ... For YIQ, YUV and OHTA use the red channel. For example, OHTA is a principal components transformation that puts most of the information in the first channel. Here we have ... -colorspace OHTA -channel red -equalize -colorspace RGB ... evaluate an arithmetic, relational, or logical expression. Choose from:
Add And Divide LeftShift Log Max Min Multiply Or Pow RightShift Set Subtract Xor The function will modify each of the color values for the specified -channel in the image. The values are not normalized, but are modified as 0 to QuantumRange. The transparency channel of the image is represented as a 'alpha' values (0 - fully transparent), so divide an alpha channel value by 2 will make the image semi-transparent. Percentage '%' can be used to specify a value as a percentage of the QuantumRange. To print a complete list of evaluate operators, use the -list evaluate option. Pow has been added as of IM 6.4.1-9, and works on normalized color values. Note that Pow is equivalent to the -gamma operator. For example -gamma 2 would be equivalent to -evaluate pow 0.5 or a 'square root' function. The value used with -gamma is just the inverse of the value used with Pow. Log has been added as of IM 6.4.2-1 and works on normalize color values. This is a "scaled" log function. The constant used with Log provides a "scaling factor" that adjusts the curvature in the graph of the log function. The formula on normalize values is log(constant*value)/log(constant+1). The Add, Subtract and Multiply methods can also be achieved sing either the -level or the +level operator with appropriate argument to linearly modify the overall range of color values. Please note however that -level treats transparency as 'matte' values (0 = opaque), while -evaluate works with 'alpha' values. set the image size and offset. If the image is enlarged, unfilled areas are set to to the background color. See -resize for details about the geometry specification. extract the specified area from image. The option is most useful for extracting a subregion of a very large raw image. Note, these two command are equivalent: convert -size 16000x16000 -depth 8 -extract 640x480+1280+960 image.rgb image.png convert -size 16000x16000 -depth 8 image.rgb[640x480+1280+960]' image.rgb image.png color to use when filling a graphic primitive. This option accepts a color name, a hex color, or a numerical RGB, RGBA, HSL, HSLA, CMYK, or CMYKA specification. See Color Names for a description of how to properly specify the color argument. Enclose the color specification in quotation marks to prevent the "#" or the parentheses from being interpreted by your shell. For example, convert -fill blue ... convert -fill "#ddddff" ... convert -fill "rgb(255,255,255)" ... See -draw for further details. To print a complete list of color names, use the -list color option. use this type of filter when resizing an image. Use this option to affect the resizing operation of an image (see -resize). For example you can use a simple resize filter such as: Point Hermite Cubic Box Gaussian Catrom Triangle Quadratic Mitchell The Bessel and Sinc filter is also provided, but are by default blackman-windowed. However these filters define a windowing filter for the Sinc or Bessel filter function, as appropriate for the scaling operator used (usally Sinc for orthogonal -resize). Windowed filters include: Lanczos Hamming Parzen Blackman Kaiser Welsh Hanning Bartlet Bohman Also one special self-windowing filter is also provided Lagrange, which will automatically re-adjust its function depending on the current 'support' or 'lobes' expert settings (see below). If you do not select a filter with this option, the filter defaults to Mitchell for a colormapped image, a image with a matte channel, or if the image is enlarged. Otherwise the filter default to Lanczos. To print a complete list of resize filters, use the -list filter option. You can modify how the filter behaves as it scales your image through the use of these expert settings:
For example, to get a 8 lobe Lanczos-Bessel filter:
convert image.png -filter bessel \
-set filter:window=bessel -set filter:lobes=8 \
-resize 150% image.jpg
Or a raw un-windowed Sinc filter with 4 lobes:
convert image.png -set filter:filter=sinc -set filter:lobes=4 \
-resize 150% image.jpg
Note that the use of expert options (except for 'blur' with simple resize filters), are provided for image processing experts who have studied and understood how resize filters work. Without this knowledge, and an understanding of the defination of the actual filters involved, using expert settings are more likely to be detremental to your image resizing. a simple alias for the -layers method "flatten" create a mirror image. reflect the scanlines in the vertical direction. floodfill the image with color at the specified offset. Using -fuzz to floodfill pixels which only change by a small amount. create a mirror image. reflect the scanlines in the horizontal direction. set the font to use when annotating images with text, or creating labels. To print a complete list of fonts, use the -list font option (for versions prior to 6.3.6, use 'type' instead of 'font'). In addition to the fonts specified by the above pre-defined list, you can also specify a font from a specific source. For example Arial.ttf is a TrueType font file, ps:helvetica is PostScript font, and x:fixed is X11 font. define the foreground color. The color is specified using the format described under the -fill option. the image format type. When used with the mogrify utility, this option converts any image to the image format you specify. For a list of image format types supported by ImageMagick, see the output of this command: identify -list format. By default the file is written to its original name. However, if the filename extension matches a supported format, the extension is replaced with the image format type specified with -format. For example, if you specify tiff as the format type and the input image filename is image.gif, the output image filename becomes image.tiff. output formatted image characteristics. See Format and Print Image Properties for an explanation on how to specify the argument to this option. surround the image with an ornamental border. See -resizefor details about the geometry specification. The -frame option is not affected by the -gravity option. The color of the border is specified with the -mattecolor command line option. include the X window frame in the imported image. colors within this distance are considered equal. A number of algorithms search for a target color. By default the color must be exact. Use this option to match colors that are close to the target color in RGB space. For example, if you want to automatically trim the edges of an image with -trim but the image was scanned and the target background color may differ by a small amount. This option can account for these differences. The distance can be in absolute intensity units or, by appending % as a percentage of the maximum possible intensity (255, 65535, or 4294967295). apply a mathematical expression to an image or image channels. If the first character of expression is @, the expression is read from a file titled by the remaining characters in the string. See FX, The Special Effects Image Operator for a detailed discussion of this option. level of gamma correction. The same color image displayed on two different workstations may look different due to differences in the display monitor. Use gamma correction to adjust for this color difference. Reasonable values extend from 0.8 to 2.3. Gamma less than 1.0 darkens the image and gamma greater than 1.0 lightens it. Large adjustments to image gamma may result in the loss of some image information if the pixel quantum size is only eight bits (quantum range 0 to 255). Gamma adjusts the image's channel values pixel-by-pixel according to a power law, namely, pow(pixel,1/gamma) or pixel^(1/gamma), where pixel is the normalized or 0 to 1 color value. For example, using a value of gamma=2 will be the same as taking the square root of the image. You can apply separate gamma values to the red, green, and blue channels of the image with a gamma value list delimited with commas (e.g., 1.7,2.3,1.2). Use +gamma value to set the image gamma level without actually adjusting the image pixels. This option is useful if the image is of a known gamma but not set as an image attribute (e.g. PNG images). Note that gamma adjustments is also available via the -level operator blur the image with a Gaussian operator. Convolve the image with a Gaussian or normal distribution. The formula is: where r is the blur radius (r2 = u2 + v2), and σ is the standard deviation of the Gaussian distribution. As a guideline, set r to approximately 3σ. Specify a radius of 0 and ImageMagick selects a suitable radius for you. preferred size and location of the image. If the x is negative, the offset is measured leftward from the right edge of the screen to the right edge of the image being displayed. Similarly, negative y is measured between the bottom edges. The offsets are not affected by %; they are always measured in pixels. direction primitive gravitates to when annotating the image. Choices are: NorthWest, North, NorthEast, West, Center, East, SouthWest, South, SouthEast. Or you can use -list with a 'Gravity' option to get a complete list of -gravity settings available in your ImageMagick installation. The direction you choose specifies where to position the text when annotating the image. For example, a gravity of Center forces the text to be centered within the image. By default, the image gravity is NorthWest. See -draw for more details about graphic primitives. Only the text primitive is affected by the -gravity option. The -gravity option is also used in concert with the -geometry option and other options that take geometry as a parameter, such as the -crop option. See -geometry for details of how the -gravity option interacts with the x and y parameters of a geometry specification. When used as an option to composite, -gravity gives the direction that the image gravitates within the composite. When used as an option to montage, -gravity gives the direction that an image gravitates within a tile. The default gravity is Center for this purpose. green chromaticity primary point. print usage instructions. when comparing images, highlight pixel differences with this color. specify the icon geometry. Offsets, if present in the geometry specification, are handled in the same manner as the -geometry option, using X11 style to handle negative offsets. iconic animation. identify the format and characteristics of the image. This information is printed: image scene number; image name; image size; the image class (DirectClass or PseudoClass); the total number of unique colors; and the number of seconds to read and transform the image. Refer to MIFF for a description of the image class. If -colors is also specified, the total unique colors in the image and color reduction error values are printed. Refer to color reduction algorithm for a description of these values. If -verbose preceds this option, copious amounts of image properties are displayed including image statistics, profiles, image histogram, and others. make image immutable. implode image pixels about the center. insert the last image into the image sequence. This option takes last image in the current image sequence and inserts it at the given index. If a negative index is used, the insert position is calculated before the last image is removed from the sequence. As such -insert -1 will result in no change to the image sequence. The +insert option is equivalent to -insert -1. In other words, insert the last image, at the end of the current image sequence. Consequently this has no effect on the image sequence order. use this type of rendering intent when managing the image color. Use this option to affect the color management operation of an image (see -profile). Choose from these intents: Absolute, Perceptual, Relative, Saturation. The default intent is undefined. To print a complete list of rendering intents, use the -list intent option. the type of interlacing scheme. Choose from: none line plane partition JPEG GIF PNG This option is used to specify the type of interlacing scheme for raw image formats such as RGB or YUV. None means do not interlace (RGBRGBRGBRGBRGBRGB...), Line uses scanline interlacing (RRR...GGG...BBB...RRR...GGG...BBB...), and. Plane uses plane interlacing (RRRRRR...GGGGGG...BBBBBB...). Partition is like plane except the different planes are saved to individual files (e.g. image.R, image.G, and image.B). Use Line or Plane to create an interlaced PNG or GIF or progressive JPEG image. To print a complete list of interlacing schemes, use the -list interlace option. The pixel color interpolation method to use when looking up a color basied on a floating point or real value. When looking up the color of a pixel using a non-interger floating point value, you typically fall in between the pixel colors defined by the source image. This setting determines how the color is determined from the colors of the pixels surrounding that point. That is how to determine the color of a point that falls between two, or even four different colored pixels. integer: The color of the top-left pixel (floor function) nearest-neighbor: The nearest pixel to the lookup point (rounded function) average: The average color of the surrounding four pixels bilinear A double linear interpolation of pixels (the default) mesh Divide area into two flat triangular interpolations bicubic Fitted bicubic-spines of surrounding 16 pixels spline Direct spline curves (colors are blurred) filter Use resize -filter settings This is most important for distortion operators such as -distort, -implode, -transform and -fx. To print a complete list of interpolation methods, use the -list interpolate option. See also -virtual-pixel, for control of the lookup for positions outside the boundaries of the image. assign a label to an image. Use this option to assign a specific label to the image, as it is read in or created. You can use the -set operation to re-assign a the labels of images already read in. Image formats such as TIFF, PNG, MIFF, supports saving the label information with the image. When saving an image to a PostScript file, any label assigned to an image will be used as a header string to print above the postscript image. You can include the image filename, type, width, height, or other image attribute by embedding special format character. See -format for details of the percent escape codes. For example, -label "%m:%f %wx%h" bird.miff assigns an image label of MIFF:bird.miff 512x480 to the "bird.miff" image and whose width is 512 and height is 480, as it is read in. If a +label option was used instead, any existing label present in the image would be used. You can remove all labels from an image by assigning the empty string. A label is not drawn on the image, but is embedded in the image datastream via a Label tag or similar mechanism. If you want the label to be visible on the image itself, use the -draw option, or during the final processing in the creation of a image montage. The label font can be specified with -font, and the other font attribute settings. If the first character of string is @, the image label is read from a file titled by the remaining characters in the string. Labels in a file are literal, no embedded formatting characters are recognized. perform local adaptive threshold. Perform local adaptive threshold using the specified width, height, and offset. The offset is a distance in sample space from the mean, as an absolute integer ranging from 0 to the maximum sample value or as a percentage. handle multiple images forming a set of image layers or animation frames. Perform various image operation methods to a ordered sequence of images which may represent either a set of overlaid 'image layers', a GIF disposal animation, or a fully-'coalesced' animation sequence.
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