GRAPHICS PRO

November '20

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G R A P H I C S - P R O. C O M 2 0 2 0 N O V E M B E R G R A P H I C S P R O 5 5 off (0), or on (1). With only one switch, the light is either on, displaying white, or off, displaying black. EIGHT BIT GRAYSCALE Grayscale pixels contain eight bits of in- formation. Translated into our light switch analogy, each pixel has eight switches that can be turned on or off. With eight switches each with a power of two, 256 combinations of tonal values can be achieved (2 8 = 256). Each gray value is assigned a number be- tween zero (black) and 255 (white). The potential of 256 gray values when seen on screen or translated into printer dots pro- duces the illusion of continuous tone. A closer look, however, reveals that they are a mosaic of varying shades of gray pixels (Fig- ure 4). Low grayscale values produce darker grays with the number zero being assigned to absolute black. Conversely, high values produce lighter colors with the number 255 assigned to white. Of course, in a 256-level grayscale, a value of 127 is a mid-tone gray. RED, GREEN, BLUE Color images are actually composed of three grayscale channels. That may sound contra- dictory, but the concept is rather simple. Bitmap and grayscale images contain only one channel: a single image in the Chan- nels panel that is identical to the image on screen. RGB images contain three channels that are grayscales displayed through red, green, and blue color filters (Figure 5). Each grayscale pixel can contain eight bits of information or a maximum of 256 shades of gray. RGB images display a multitude of variations of color. In fact, with three chan- nels of 256 variations, there are almost 17 million colors (256 3 = 16,777,216), which is the extent of your color palette in Pho- toshop or any other graphics program that supports RGB images. As with grayscales, darker colors have lower numbers and light- er colors have higher numbers. GRAY VERSUS COLOR When the RGB values of a pixel are all equal, then the color produced will be black (0R, 0G, 0B), white (255R, 255G, 255B), or gray (any other numbers between zero and 256 with three equal RGB numbers). Pixels appear colored when their RGB numbers are unequal. For example, a color with higher red numbers and lower green and blue numbers is predominantly red. HSB, CMYK, AND LAB Software automatically converts RGB val- ues into other color models. The color of pixels can be interpreted in hue, saturation, and brightness (HSB); cyan, magenta, yel- low, and black (CMYK); and red/green (A), blue/yellow (B), and lightness (L)—LAB (Figure 6). Color models are simply differ- ent interpretations of color values for spe- cific purposes. HSB, for example, divides color into its basic physical components. Hue is the posi- tion of the color on the color wheel in de- grees, saturation, its strength in percentages, www.leister.com SOLANO AT: lighter, quieter and more durable than any other hot-air tool. We know how. SOLANO AT Light, quiet, durable

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