(PHP 4 >= 4.3.2, PHP 5, PHP 7)
imagecolorallocatealpha — Allocate a color for an image
$image
, int $red
, int $green
, int $blue
, int $alpha
)
imagecolorallocatealpha() behaves identically to
imagecolorallocate() with the addition of the transparency
parameter alpha.
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.
red, green
and blue parameters are integers
between 0 and 255 or hexadecimals between 0x00 and 0xFF.
A color identifier or FALSE if the allocation failed.
This function may
return Boolean FALSE, but may also return a non-Boolean value which
evaluates to FALSE. Please read the section on Booleans for more
information. Use the ===
operator for testing the return value of this
function.
| Version | Description |
|---|---|
| 5.1.3 |
Returns FALSE if the allocation failed. Previously
-1 was returned.
|
Example #1 Example of using imagecolorallocatealpha()
<?php
$size = 300;
$image=imagecreatetruecolor($size, $size);
// something to get a white background with black border
$back = imagecolorallocate($image, 255, 255, 255);
$border = imagecolorallocate($image, 0, 0, 0);
imagefilledrectangle($image, 0, 0, $size - 1, $size - 1, $back);
imagerectangle($image, 0, 0, $size - 1, $size - 1, $border);
$yellow_x = 100;
$yellow_y = 75;
$red_x = 120;
$red_y = 165;
$blue_x = 187;
$blue_y = 125;
$radius = 150;
// allocate colors with alpha values
$yellow = imagecolorallocatealpha($image, 255, 255, 0, 75);
$red = imagecolorallocatealpha($image, 255, 0, 0, 75);
$blue = imagecolorallocatealpha($image, 0, 0, 255, 75);
// drawing 3 overlapped circle
imagefilledellipse($image, $yellow_x, $yellow_y, $radius, $radius, $yellow);
imagefilledellipse($image, $red_x, $red_y, $radius, $radius, $red);
imagefilledellipse($image, $blue_x, $blue_y, $radius, $radius, $blue);
// don't forget to output a correct header!
header('Content-Type: image/png');
// and finally, output the result
imagepng($image);
imagedestroy($image);
?>
The above example will output something similar to:
Note: This function requires GD 2.0.1 or later (2.0.28 or later is recommended).