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Scenario 2
White Reference Black Reference
red = 63 red = 4
green = 127 green = 0
blue = 31 blue = 0
Using these reference values, 50% blue for scenario 1 is 31,
and 50% blue for scenario 2 is 15.
Color Selection The HP color printers offer two methods for selecting colors:
Indexed selection
Direct selection
In indexed selection, colors are chosen using their palette
index numbers. For non-raster mode, the palette index
number is specified using the Foreground Color command.
In raster mode, the data bit combination for each pixel
forms an index number. The example below shows how the
index numbers for an 8-color palette are specified:
Three-bit combinations: 0 1 0 1 0 1 0 1
0 0 1 1 0 0 1 1
0 0 0 0 1 1 1 1
Palette index number: 0 1 2 3 4 5 6 7
The number of colors in the palette dictates the number of
bits per pixel of raster data required to specify an index
number. For example, to specify 256 colors you need to send
8 bits of raster data per pixel (2
8
= 256).
In direct selection, colors are specified using the proportions
of their primary components. For example, using a
24-bit-per- pixel representation, the color specified by (0xff,
0xf0, 0x00) for red, green, and blue would print a slightly
red-tinted yellow. A palette is not used for direct selection.
Pixel Encoding Colors are encoded in a row of raster data using either
plane or pixel format. In planar format, all the pixels in a
row are partially specified by one plane (bit) before the next
Color Printing Overview 1-5Color Printing Overview 1-5