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imagecolorset

(PHP 4, PHP 5, PHP 7, PHP 8)

imagecolorset — Set the color for the specified palette index

Description

imagecolorset(
 GdImage $image,
 int $color,
 int $red,
 int $green,
 int $blue,
 int $alpha = 0
): ?false

This sets the specified index in the palette to the specified color. This is useful for creating flood-fill-like effects in palleted images without the overhead of performing the actual flood-fill.

Parameters

image

A GdImage object, returned by one of the image creation functions, such as imagecreatetruecolor().

color

An index in the palette.

red

Value of red component.

green

Value of green component.

blue

Value of blue component.

alpha

Value of alpha component.

Return Values

The function returns null on success, or false on failure.

Changelog

Version Description
8.0.0 image expects a GdImage instance now; previously, a valid gd resource was expected.

Examples

Example #1 imagecolorset() example

<?php
// Create a 300x100 image
$im = imagecreate(300, 100);

// Set the background to be red
imagecolorallocate($im, 255, 0, 0);

// Get the color index for the background
$bg = imagecolorat($im, 0, 0);

// Set the background to be blue
imagecolorset($im, $bg, 0, 0, 255);

// Output the image to the browser
header('Content-Type: image/png');

imagepng($im);
?>

See Also

© 1997–2025 The PHP Documentation Group
Licensed under the Creative Commons Attribution License v3.0 or later.
https://www.php.net/manual/en/function.imagecolorset.php