Image Stack Image Setting An image setting persists as it appears on the command-line and may affect subsequent processing such as reading an image, an image operator, or when writing an image as appropriate. An image setting stays in effect until it is reset or the command-line terminates. The image settings include: In this example, -channel applies to each of the images, since, as we mentioned, settings persist: magick -channel RGB wand. An operator is any command-line option not listed as a image setting or image sequence operator. Unlike an image setting, which persists until the command-line terminates, an operator is applied to the current image set and forgotten.
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Brightness and Contrast values apply changes to the input image. They are not absolute settings. A brightness or contrast value of zero means no change.
Positive values increase the brightness or contrast and negative values decrease the brightness or contrast. The default is to apply the same transformation to all channels. Brightness and Contrast arguments are converted to offset and slope of a linear transform and applied using -function polynomial "slope,offset".
Negative slopes, i. All achievable slopes are zero or positive. The offset varies from The default thresholds are shown. The radiusxsigma controls a gaussian blur applied to the input image to reduce noise and smooth the edges.
This option sets the caption meta-data of an image read in after this option has been given. To modify a caption of images already in memory use " -set caption". The caption can contain special format characters listed in the Format and Print Image Properties.
These attributes are expanded when the caption is finally assigned to the individual images. If the first character of string is , the image caption is read from a file titled by the remaining characters in the string. Comments read in from a file are literal; no embedded formatting characters are recognized.
Caption meta-data is not visible on the image itself. To do that use the -annotate or -draw options instead. See individual operator documentation. This is turned on by default and if set means that operators that understand this flag should perform: cross-channel synchronization of the channels. If not specified, then most grey-scale operators will apply their image processing operations to each individual channel as specified by the rest of the -channel setting completely independently from each other.
For example for operators such as -auto-level and -auto-gamma the color channels are modified together in exactly the same way so that colors will remain in-sync. Without it being set, then each channel is modified separately and independently, which may produce color distortion. That is to say it will modify the image processing with the understanding that fully-transparent colors should not contribute to the final result. How each operator does this depends on that operators current implementation.
Not all operators understands this flag at this time, but that is changing. To print a complete list of channel types, use -list channel.
Options that are affected by the -channel setting include the following. For example -threshold will by default grayscale the image before thresholding, if no -channel setting has been defined. As an alpha channel is optional within images, some operators will read the color channels of an image as a greyscale alpha mask, when the image has no alpha channel present, and the -channel setting tells the operator to apply the operation using alpha channels.
The -clut operator is a good example of this. The expression consists of one or more channels, either mnemonic or numeric e. Here we take an sRGB image and a grayscale image and inject the grayscale image into the alpha channel: magick wizard. See Image Geometry for complete details about the geometry argument. The width and height given in the of the size portion of the geometry argument give the number of columns and rows to remove.
The offset portion of the geometry argument is influenced by a -gravity setting, if present. The -chop option removes entire rows and columns, and moves the remaining corner blocks leftward and upward to close the gaps. While it can remove internal rows and columns of pixels, it is more typically used with as -gravity setting and zero offsets so as to remove a single edge from an image.
Compare this to -shave which removes equal numbers of pixels from opposite sides of the image. Using -chop effectively undoes the results of a -splice that was given the same geometry and -gravity settings.
The image is divided into tiles of width and height pixels. The tile size should be larger than the size of features to be preserved and respects the aspect ratio of the image. The number of histogram bins should be smaller than the number of pixels in a single tile. A clip-limit of 2 to 3 is a good starting place e. Very large values will let the histogram equalization do whatever it wants to do, that is result in maximal local contrast.
The value 1 will result in the original image. Note, if the number of bins and the clip-limit are ommitted, they default to and no clipping respectively. If a clipping path is present, it is applied to subsequent operations. For example, in the command magick cockatoo. The -clip feature requires SVG support.
If the SVG delegate library is not present, the option is ignored. Use the alpha channel of the current image as a mask. Pixels in the black areas of the clip mask are modified per the requirements of the operator. In some ways this is similar to though not the same as defining a rectangular -region , or using the negative of the mask third image in a three image -composite , operation. This is identical to -clip except choose a specific clip path in the event the image has more than one path available.
Outside parenthesis not recommended it clones the images from the current image sequence. Specify the image by its index in the sequence. The first image is index 0. Specify a range of images with a dash e. Separate multiple indexes with commas but no spaces e. The second LUT image is ordinarily a gradient image containing the histogram mapping of how each channel should be modified. Typically it is a either a single row or column image of replacement color values.
If larger than a single row or column, values are taken from a diagonal line from top-left to bottom-right corners. The lookup is further controlled by the -interpolate setting, which is especially handy for an LUT which is not the full length needed by the ImageMagick installed Quality Q level. Catom can return a useful second-order continuity. This operator is especially suited to replacing a grayscale image with a specific color gradient from the CLUT image.
Only the channel values defined by the -channel setting will have their values replaced. If either the image being modified, or the lookup image, contains no transparency i.
That is you can use a grayscale CLUT image to adjust a existing images alpha channel, or you can color a grayscale image using colors form CLUT containing the desired colors, including transparency. See also -hald-clut which replaces colors according to the lookup of the full color RGB value from a 2D representation of a 3D color cube. Overlay each image in an image sequence according to its -dispose meta-data, to reproduce the look of an animation at each point in the animation sequence.
All images should be the same size, and are assigned appropriate GIF disposal settings for the animation to continue working as expected as a GIF animation. Such frames are more easily viewed and processed than the highly optimized GIF overlay images. Specify the amount of colorization as a percentage. Separate colorization values can be applied to the red, green, and blue channels of the image with a comma-delimited list of colorization values e.
The type can be shared or private. 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. If private is chosen, the image colors appear exactly as they are defined. However, other clients may go technicolor when the image colormap is installed.
The actual number of colors in the image may be less than your request, but never more. Note that this a color reduction option. Images with fewer unique colors than specified by value 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, it is more efficient to convert the image to the gray colorspace before reducing the number of colors. Refer to the color reduction algorithm for more details. This option permits saturation changes, hue rotation, luminance to alpha, and various other effects.
The matrix is similar to those used by Adobe Flash except offsets are in column 6 rather than 5 in support of CMYKA images and offsets are normalized divide Flash offset by As an example, to add contrast to an image with offsets, try this command: magick kittens. For colorspace conversion, the gamma function is first removed to produce linear RGB.
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Samule The color of the border is specified with the -mattecolor command line option. To print a complete list of -evaluate operators, use -list evaluate. Unlike the similar -frame option, -raise does not alter the dimensions of the image. The x and y offsets are treated in the same manner as in -crop. While it can remove internal rows and columns of pixels, it is more typically used with as -gravity setting and zero offsets so as to remove a single edge from an image.
How to negate image using ImageMagick
IMAGEMAGICK NEGATE PDF