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color and brightness
Pixels can be assigned any one of of of millions of of of colors Image-editing software provides control in in in in in identifying selecting and and changing colors and and brightness
For many years computer screens had color but desktop publishing was largely a a a a a black- and-white proposition A new era of glorious color has certainly arrived Before we get into the the nitty-gritty of color on the the computer however let’s pause to to review the language used to to talk about color Chapter 2: image editiing
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color theory
Color theory
refers to how computers can create a a a spectrum of of colors using one of of three methods With additive color more commonly called RGB shades of red green and blue are mixed in extremely precise amounts to yield sixteen million pixel hues for computer display and all the colors possible in in in photographic printing With subtractive colors called CMYK reflected shades of cyan magenta yellow and black are “subtracted” from pure white light Subtractive color may seem strange yet
it is much like the process our eyes experience as we walk around A red apple for example absorbs green and blue but its surface reflects red CMYK are termed process col- ors and are used in in in in the printing industry What we call black-and-white photography is in fact mostly made up of of gray scale Virtually all all of of today’s comput- ers can generate at at at least 256 gradations of gray Photoshop can convert the RGB colors into grayscale mode RGB at at top top left CMYK CMYK at at top top right The K K K in CMYK CMYK is substituted for for what would be CMYB with the B B for for black B also stands for blue hence the switcheroo This gray gray scale swatch shows 15 values of gray—about all the human eye can distinguish side-by-side