PHP imagecolorallocatealpha() Allocate color and transparency for an image Usage and Examples

PHP Image Processing

imagecolorallocatealpha — Allocate color and transparency for an image.

Syntax

int imagecolorallocatealpha ( resource $image , int $red , int $green , int $blue , int $alpha )

The behavior of imagecolorallocatealpha() is the same as imagecolorallocate(), but with an additional transparency parameter alpha, whose value ranges from 0 to 127.0 represents completely opaque,127 represents completely transparent.

Returns FALSE if allocation fails.

Note:This function requires GD 2.0.1 or higher version (recommended 2.0.28 and higher versions).

Example

<?php
$size　=　300;
$image=imagecreatetruecolor($size, $size);
//　Draw a box with white background and 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 some colors using the alpha value
$yellow = imagecolorallocatealpha($image,　255,　255, 0,　75);
$red = imagecolorallocatealpha($image,　255, 0, 0,　75);
$blue = imagecolorallocatealpha($image, 0, 0,　255,　75);
//　Draw three overlapping circles
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, $blue);
//　Do not forget to output the correct header!
header('Content-type: image/png');
//　The final output result
imagepng($image);
imagedestroy($image);
?>

The image of the output result of the above example is as follows:

Related articles

• imagecolorallocate() Allocate colors for an image.

• imagecolordeallocate() Deallocate the allocation of image colors.

PHP Image Processing