(PHP 4 >= 4.0.6, PHP 5, PHP 7)
imagecolorexactalpha — Get the index of the specified color + alpha
$image
, int $red
, int $green
, int $blue
, int $alpha
)Returns the index of the specified color+alpha in the palette of the image.
imageAn image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
redValue of red component.
greenValue of green component.
blueValue of blue component.
alphaA value between 0 and 127. 0 indicates completely opaque while 127 indicates completely transparent.
Returns the index of the specified color+alpha in the palette of the image, or -1 if the color does not exist in the image's palette.
Example #1 Get colors from the GD logo
<?php
// Setup an image
$im = imagecreatefrompng('./gdlogo.png');
$colors = Array();
$colors[] = imagecolorexactalpha($im, 255, 0, 0, 0);
$colors[] = imagecolorexactalpha($im, 0, 0, 0, 127);
$colors[] = imagecolorexactalpha($im, 255, 255, 255, 55);
$colors[] = imagecolorexactalpha($im, 100, 255, 52, 20);
print_r($colors);
// Free from memory
imagedestroy($im);
?>
The above example will output something similar to:
Array
(
[0] => 16711680
[1] => 2130706432
[2] => 939524095
[3] => 342163252
)
Note: This function requires GD 2.0.1 or later (2.0.28 or later is recommended).
Note that a color allocated with imagecolorexactalpha won't show alpha (it will be opaque) when used with imageline(). Use imagerectangle() set to your normal start and end points instead.
Ensure that the image is created via imagecreatetruecolor() as well!
What might be misleading in the docs is that if the specified color + alpha channel does not exist it will be created. So if you like to use an alpha channel in your image enable alpha blending and then create you color using this method.
