Color Quantization

Functions for truecolor to palette conversion

Summary

Color Quantization	Functions for truecolor to palette conversion
Functions
gdImageTrueColorToPaletteSetMethod	Selects the quantization method
gdImageTrueColorToPaletteSetQuality	Chooses a quality range for quantization
gdImageCreatePaletteFromTrueColor	Creates a new palette image from a truecolor image
gdImageTrueColorToPalette	Converts a truecolor image to a palette image

int gdImageTrueColorToPaletteSetMethod ( gdImagePtr im,
int method,
int speed )

Selects the quantization method

That quantization method is used for all subsequent gdImageTrueColorToPalette and gdImageCreatePaletteFromTrueColor calls.

im	The image.
method	The quantization method, see gdPaletteQuantizationMethod.
speed	The quantization speed between 1 (highest quality) and 10 (fastest). 0 selects a method-specific default (recommended).

Zero if the given method is invalid or not available; non-zero otherwise.

void gdImageTrueColorToPaletteSetQuality ( gdImagePtr im,
int min_quality,
int max_quality )

Chooses a quality range for quantization

That quality range is used in all subsequent calls to gdImageTrueColorToPalette and gdImageCreatePaletteFromTrueColor if the quantization method is GD_QUANT_LIQ.

im	The image.
min_quality	The minimum quality in range 1-100 (1 = ugly, 100 = perfect). If the palette cannot represent the image with at least min_quality, then no conversion is done.
max_quality	The maximum quality in range 1-100 (1 = ugly, 100 = perfect), which must be higher than the min_quality. If the palette can represent the image with a quality better than max_quality, then fewer colors than requested will be used.

gdImagePtr gdImageCreatePaletteFromTrueColor ( gdImagePtr im,
int dither,
int colorsWanted )

Creates a new palette image from a truecolor image

im	The image.
dither	Whether dithering should be applied.
colorsWanted	The number of desired palette entries.

A newly create palette image; NULL on failure.

int gdImageTrueColorToPalette ( gdImagePtr im,
int dither,
int colorsWanted )

Converts a truecolor image to a palette image

im	The image.
dither	Whether dithering should be applied.
colorsWanted	The number of desired palette entries.

Non-zero if the conversion succeeded, zero otherwise.