PHP Manual
GD and Image Functions
Get the index of the specified color + alpha or its closest possible alternative

imagecolorresolvealpha

(PHP 4 >= 4.0.6, PHP 5, PHP 7, PHP 8)

imagecolorresolvealpha — Get the index of the specified color + alpha or its closest possible alternative

Description

imagecolorresolvealpha(
    GdImage $image,
    int $red,
    int $green,
    int $blue,
    int $alpha
): int

This function is guaranteed to return a color index for a requested color, either the exact color or the closest possible alternative.

Parameters

image: A GdImage object, returned by one of the image creation functions, such as imagecreatetruecolor().
red: Value of red component.
green: Value of green component.
blue: Value of blue component.
alpha: A value between 0 and 127. 0 indicates completely opaque while 127 indicates completely transparent.

The colors parameters are integers between 0 and 255 or hexadecimals between 0x00 and 0xFF.

Return Values

Returns a color index.

Changelog

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

Examples

Example #1 Using imagecoloresolvealpha() to get colors from an image

<?php
// Load an image
$im = imagecreatefromgif('phplogo.gif');

// Get closest colors from the image
$colors = array();
$colors[] = imagecolorresolvealpha($im, 255, 255, 255, 0);
$colors[] = imagecolorresolvealpha($im, 0, 0, 200, 127);

// Output
print_r($colors);
?>

The above example will output something similar to:

Array
(
    [0] => 89
    [1] => 85
)