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1-8 Color Printing Overview EN
The PCL 5 color command set supports several Pixel Encoding
Modes. The PEMs are categorized first by whether the pixel is an
index into a palette, or a color specification. The other PEM
categorization is whether the pixel data is divided into planes and
transferred one plane at a time or is transferred in sequential order.
There are four supported Pixel Encoding modes:
1 Indexed by Plane
2 Indexed by Pixel
3 Direct by Plane
4 Direct by Pixel (also known as 24-bit direct).
For example, the format known as direct by plane, uses a 3-bit pixel
where the first bit indicates the presence or absence of a red dot, the
second a green dot and the third a blue dot. The data is still arranged
in rows, but all the red data is sent, then the green and finally all the
blue. The example below represents the commands to transfer an
image with the direct by plane PEM. The underlined bits, while
transferred separately, are logically from the same pixel.
The direct by pixel PEM uses only the row transfer command. Each
pixel is composed of three bytes, one byte per component of the color
specification. All the bytes of a given pixel are transferred before the
next one is transferred.
The indexed by pixel PEM is similar to the direct pixel PEM but the
pixel occupies at most one byte and is an index into the current
palette.
The indexed by plane PEM is similar to the direct by plane PEM
except the pixel's value is an index into the current palette. The use of
this mode is discouraged due to the extra processing required to
combine the bits from each plane into a single number, which is then
used as an index into the current palette.
?*b#V row 1 plane 1 (red) b1 b1 b1 b1 b1 b1...
?*b#V plane 2 (green) 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...
?*b#W row x b1 b2 b3 b1 b2 b3 b1...