Note that if given a grayscale image, all the colorspace grayscale imagesproduce exactly the same image as the input greyscale image, with theexception of 'Lightness*' ('') channel image for a LAB / LUVcolorspace.
Note that 'Gray' (also known as 'Intensity' or more exactly 'Luminance') andthe 'Luma' of the YUV colorspace are equivalent. Similarly 'Brightness' ofHSB colorspace, and the Negated 'blacK' channel of CMYK colorspace, areequivalent (and typically overly bright for grey-scale usage).
The '' colorspace is based on the ''colorspace, which is a cylindrical representation of the ''colorspace, though with a simpler formula for the lightness channel, so as togenerate pure white at maximum lightness.
It is recommended you use this colorspace for hue rotations, so as to preservethe general brightness of all the colors in the image. See the examples in .
As of IM version 6.3.7-10, the 'plus' versions of these operators inverts thecolor selection. That is, the colors that do NOT match the given color willbe replaced. For example here I replace any color that is NOT pure-black,with white, leaving just the pure black borders of the image.
It can be difficult to find a specific named color to use. But by loading theimage to the right in the IM "" program you can use the middle mouse button to look atthe ImageMagick color name for the specific color that has been plotted.
Here for example are red-blue blurs in the 3 main linear colorspaces.I picked these colors as they appear to show the greatest difference,in the intermedite colors generated.
All the above 'named' colors are in sRGB colorspace, which is the colorspacethey were defined in. But sometimes you want to define a color in a differentcolorspace. For example, in HSL, or CYMK, or even as a XYZ color. Imagemagickcan do this and you can see the details of these specifications in .
Don't think of the 'R' or 'Red' channel as being red, think of it as 'channel1' which could contain data for 'red', 'hue', 'cyan', or other things dependingon the colorspace of the the image. 'Red' is just a label for the channeltypically used for 'red', or the first channel.
Basically when processing images that involve mixing colors, for example inoperations such as (color reduction), but also in andmore generally , you shouldprocess the images in a linear colorspace for the more accurate results,though in reality few people do this.
As this is very common the 'RGB' channels also have an alternative naming of'Cyan', 'Magenta', and 'Yellow', or just the letters 'C', 'M' and 'Y', thoughin reality they refer to the same set of channels that is used for'' images. A special fourth color channel is also added forthe 'Black' or 'K' color channel.
The same thing happens for other colorspaces. For example usinga '' color space means the 'Red' channel contains the'Lightness' value, while 'Green' channel holds the 'A' (or red-green) value,and 'Blue' channel holds the 'B' (or blue-yellow) value.
Gamma correction is only a rough 'quick' method of adjusting the colors tomake an image 'look' correct. It is not the usual or even the best method ofcorrecting a image for human response.
We dont know much about the resistance since much of their work was secretive and the Kuwaiti government was very reticent to say what they were doing. When asked about the feats of the resistance movement inside the government supplied no details. During the war we didnt hear much about them, but after the war many Kuwaiti patriotic posters that were alleged to have been made and placed on walls during the war were available for purchase. This sudden appearance of the posters may be explained by Richard Johnsons comments in
Using other colorspaces can be useful. For example here I take the built-inrose image and want to negate the luminance channel of the image in'' colorspace. When finished I re-combine to build a sRGBimage again.