imagecolorallocatealpha

Description

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 which may have a value between 0 and 127. 0 indicates completely opaque while 127 indicates completely transparent.

Returns FALSE if the allocation failed.

Esempio 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); ?>

See also imagecolorallocate() and imagecolordeallocate().