Programming Web Graphics with Perl and GNU Softwar

Color Control, Palettes, and Patterns

A color is represented by an anonymous array of three elements representing the red, green, and blue values:

my $red = [ 255, 0, 0 ];

The Gimp comes with several default patterns, palettes, and gradients, all of which may be referred to by name:

# Set the current pattern
my $pattern = "Blob1";
gimp_patterns_set_pattern($pattern);

# Convert $image to an indexed palette
my $palette = "Reds_And_Purples";
gimp_convert_indexed_palette($image, 1, 4, 0, $palette);

# Set the active gradient
my $gradient = "Mexican_flag_smooth";
gimp_gradients_set_active($gradient);

Table C-4. Procedures for Manipulating the Colors in an Image, and Managing Palettes and Patterns

Name	Description	Arguments
gimp_brightness_contrast	Modify brightness/contrast in the specified drawable	image (Image) The image drawable (Drawable) The drawable brightness (Integer) Brightness adjustment in the range -127 to 127 contrast (Integer) Constrast adjustment in the range -127 to 127
gimp_color_balance	Modify the color balance of the specified drawable	image (Image) The image drawable (Drawable) The drawable transfer_mode (Integer) Transfer mode 0 Shadows 1 Midtones 2 Highlights preserve_lum (Integer) Preserve luminosity values at each pixel cyan_red (Float) Cyan-Red color balance in the range -100 to 100 magenta_green (Float) Magenta-Green color balance in the range -100 to 100 yellow_blue (Float) Yellow-Blue color balance in the range -100 to 100
gimp_color_picker	Determine the color at the ...