PHP | imagecolorset() Function

Last Updated : 17 Jan, 2022

The imagecolorset() function is an inbuilt function in PHP which is used to set the color for the specified palette index. It is used to specify the index in the palette to the specified color. To perform the actual flood-fill, it is useful to create the flood-fill-like effects in palleted images without the overhead.
Syntax:

void imagecolorset ( $image, $index, $red, $green, $blue, $alpha )

Parameters: This function accepts six parameters as mentioned above and described below:

$image: It is returned by one of the image creation functions, such as imagecreatetruecolor(). It is used to create size of image.
$index: This parameter is the index value in the palette image.
$red: This parameter is used to set value of red color component.
$green: This parameter is used to set value of green color component.
$blue: This parameter is used to set value of blue color component.
$alpha: This parameter is used to set the transparency of image. The value of $alpha lies between 0 to 127 where 0 represents completely opaque while 127 represents completely transparent.

Return Value: This function does not return any value.
Below programs illustrate the imagecolorset() function in PHP:
Program 1:

php

<?php
 
// Create an image of given size
$image = imagecreate(500, 300);
 
// Set the background 
imagecolorallocate($image, 0, 0, 0);
 
// Get the color index for the background
$bg = imagecolorat($image, 150, 100);
 
// Change the background color
imagecolorset($image, $bg, 0, 153, 0);
 
// Output of the image
header('Content-Type: image/png');
 
imagepng($image);
imagedestroy($image);
?>

Output:

Program 2:

php

<?php
 
// Create an image of given size
$image = imagecreate(500, 300);
 
// Set the background 
imagecolorallocate($image, 0, 0, 0);

// set the colors of image
$white_color = imagecolorallocate($image, 255, 255, 255);

// draw the head
imagearc($image, 200, 150, 200, 200,  0, 360, $white_color);
 
// Get the color index for the background
$bg = imagecolorat($image, 150, 100);
 
// Set the background
imagecolorset($image, $bg, 0, 153, 0);
 
// Output the image to the browser
header('Content-Type: image/png');
 
imagepng($image);
imagedestroy($image);
?>