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imagecolorallocatealpha
Allocate a color for an image
(PHP 4 >= 4.3.2, PHP 5)
int imagecolorallocatealpha ( resource image, int red, int green, int blue, int alpha )
imagecolorallocatealpha() behaves identically to imagecolorallocate() with the addition of the transparency parameter alpha.
Parameters
- 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
0and127.0indicates completely opaque while127indicates completely transparent.
The colors parameters are integers between 0 and 255 or hexadecimals between 0x00 and 0xFF.
Examples
Example 990. 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:
