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

imagecolorexactalphaGet the index of the specified color + alpha


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

Returns the index of the specified color+alpha in the palette of the image.

Elenco dei parametri


Una risorsa immagine, restituita da una delle funzioni di creazione immagine, come imagecreatetruecolor().


Valore della componente rossa.


Valore della componente verde.


Valore della componente blu.


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.

Valori restituiti

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.

Log delle modifiche

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


Example #1 Get colors from the GD logo


// 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);


// Free from memory

Il precedente esempio visualizzerĂ  qualcosa simile a:

    [0] => 16711680
    [1] => 2130706432
    [2] => 939524095
    [3] => 342163252

Vedere anche:

add a note add a note

User Contributed Notes 2 notes

matt at matt-darby dot com
18 years ago
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!
phpdoc-comment at aditus dot nu
21 years ago
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.
To Top