HP PCL/PJL reference (PCL 5 Color) - Technical Reference Manual

EN Color Printing Overview 1-7
z An RGB, eight-entry palette with the following colors
starting at index 0: black, red, green, yellow, blue,
magenta, cyan, and white.
z A CMY, eight-entry palette with the following colors
starting at index 0: white, cyan, magenta, blue, yellow,
green, red and black.
• PCL Imaging mode is entered with the Configure Image Data
command that creates a programmable palette of a
programmed size. This palette can be programmed using the
color component and set index commands.
• HP-GL/2 Imaging mode is entered when HP GL/2 mode is
entered and the initialize command IN creates a
programmable palette that is shared between PCL and
HP-GL/2.
Any and all of the modes can be used on a page. For example, you
could enter the Simple Color mode to print a headline and bar chart,
PCL imaging mode to print a photographic image, and
Black-and-White mode for the text on the page. Each mode is
described in more detail in Chapter 2. “Using Color Modes.”
PCL 5 Raster Images
Monochrome PCL 5 raster images are made up of a series of zeros
and ones. A one indicates that a black dot should be deposited, a
zero indicates no dot, letting the white background show through. A
one-inch wide image with a resolution of 600 dots per inch (DPI) has
600 consecutive zeros and/or ones, which represent a horizontal slice
through the image starting at the left edge of the image. This slice is
known as a raster row. For an image one inch high and one inch wide,
at 600 dpi there are 600 hundred rows of 600 zeros and/or ones.
Color raster images follow the same conventions with this major
exception: the representation of a dot is changed from a single zero
or one to a color specification (a pixel).
Pixels and Pixel Encoding
Raster images can be thought of as being composed of a series of
pixels (picture elements). In the case of monochrome raster images,
a pixel is a single bit which takes on a value of zero or one. In color
images a pixel is essentially a color specification. However, there are
several ways of specifying a color, and how the color is specified is
called the Pixel Encoding Mode (PEM).