(PHP 4 >= 4.0.6, PHP 5, PHP 7)
imagecolorresolvealpha — Get the index of the specified color + alpha or its closest possible alternative
imagecolorresolvealpha ( resource $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.
image
An image resource, 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.
Returns a color index.
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($colors);
imagedestroy($im);
?> The above example will output something similar to:
Array
(
[0] => 89
[1] => 85
)
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https://www.php.net/manual/en/function.imagecolorresolvealpha.php