PixelPacket Structure

The PixelPacket structure is used to represent pixels in ImageMagick. ImageMagick may be compiled to support 32 or 64 bit pixels. The size of PixelPacket is controlled by the value of the QuantumDepth define. The default is 64 bit pixels, which provide the best accuracy. If memory consumption must be minimized, or processing time must be minimized, then ImageMagick may be compiled with QuantumDepth=8. The following table shows the relationship between QuantumDepth, the type of Quantum, and the overall PixelPacket size.

Effect Of QuantumDepth Values

QuantumDepth

Quantum Type

PixelPacket Size

8

unsigned char

32 bits

16

unsigned short

64 bits

The members of the PixelPacket structure, and their interpretation, are shown in the following table:

PixelPacket Structure Members

Member

Type

Interpretation

RGBColorspace

RGBColorspace + matte

CMYKColorspace

red

Quantum

Red

Red

Cyan

green

Quantum

Green

Green

Magenta

blue

Quantum

Blue

Blue

Yellow

opacity

Quantum

Ignored

Opacity

Black