By default, the image to which p, r, g, b, a, etc., are applied is the first image u in the image list, which may also be referenced using s.
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It is important to note the special role played by the first image. This is the only image in the image sequence that is modified, any other images being used only for their data. As an illustrative example, comsider the following, and note that the setting -channel red instructs -fx to modify only the red channel; nothing in the green or blue channels will change. It is instructive to ponder why the result is not symmetric.
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It is important to note the special role played by the first image. This is the only image in the image sequence that is modified, other images are used only for their data. As an illustrative example, consider the following, and note that the setting -channel red instructs -fx to modify only the red channel; nothing in the green or blue channels will change. It is instructive to ponder why the result is not symmetric.