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A-6 Color Printing Overview (Color LaserJet, 5, 5M, DeskJet) EN
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 plane is sent. In pixel format, each
pixel is fully specified before sending the next pixel.
Encoding by Plane
Planar encoding uses successive data planes, each providing one bit
for each pixel in a row. Each plane builds upon the preceding planes
until the pixels in a row are fully defined. A pixel is not fully defined
until it has received all the planes for that row.
The planes in a row form index numbers that define a pixel by
selecting a palette entry. For example, an 8-entry palette requires
3planes (2
3
= 8). The underlined bits below compose the index of the
color of the third pixel in the first row.
?*b#V row 1 plane 1 (red) b1 b1 b1 b1 b1 b1 . . .
?*b#V plane 2 (grn) b2 b2 b2 b2 b2 b2 . . .
?*b#W plane 3 (blue) b3 b3 b3 b3 b3 b3 . . .
?*b#V row 2 plane 1 (red) b1 b1 b1 b1 b1 b1 . . .