Byte 1 (Pixel Encoding Mode)

This byte designates the format of any subsequent raster images. The range of the value is zero to three. All other values for this field are ignored.

Value

Pixel Encoding

Restrictions

 

Mode

 

 

 

 

0

Indexed by Plane

Bits/Index can only be 1, 2, 3, 4, 5, 6,

 

 

7, or 8. Bit/Components 1, 2, and 3

 

 

are ignored

 

 

 

1

Indexed by Pixel

Bits/Index can only be 1, 2, 4, or 8.

 

 

Bit/Components 1, 2, and 3 are

 

 

ignored

 

 

 

2

Direct by Plane

Bits/Components 1, 2, and 3 must

 

 

be 1

 

 

 

3

Direct by Pixel

Bits/Components 1, 2, and 3 must

 

 

be 8

 

 

 

 

The number of bits per index determines the size of the palette

 

created by this command. In the case of the Indexed by Plane mode

 

the number of planes needed to represent the index is also

 

determined by the number of bits per index. Therefore, if a 256 entry

 

palette is needed, then the bits per index is set to eight since

 

28 = 256. If the Indexed by Plane mode is chosen, at most eight

 

planes are needed to represent each row of data.

 

The recommended pixel encoding mode is Direct by Pixel, since this

 

gives the most efficient raster processing. However, using this mode

 

means that delta row compression should be used since it exploits

 

redundancy between rows. Other PCL compression modes exploit

 

redundancy within a row. With Direct by Pixel the redundancy from

 

pixel to pixel in a row is masked by the differences at the byte level

 

within the pixel, that is, the differences between the red, green, and

 

blue bytes within the pixel.

 

 

Note

Raster data in Index by Plane or Direct by Plane modes cannot be

 

compressed using raster compression mode 5.

 

You need one plane or one bit/pixel for each power of two colors in the

 

 

palette. For example, a 256-color palette requires 8 planes or

 

8 bits/pixel (28 = 256).

EN

Using Color Modes 2-7

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HP L 5 manual Byte 1 Pixel Encoding Mode, Value Pixel Encoding Restrictions Mode