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Digg imagecolorallocatealpha
Allocate a color for an image
(PHP 4 >= 4.3.2, PHP 5)
imagecolorallocatealpha() behaves identically to imagecolorallocate() with the addition of the transparency parameter alpha. Parameters
The colors parameters are integers between 0 and 255 or hexadecimals between 0x00 and 0xFF. ExamplesExample 990. Example of using imagecolorallocatealpha()<?phpThe above example will output something similar to:  Code Examples / Notes » imagecolorallocatealphaeric
If you only wish to extract the alpha value for a color, you can simply extract it like so: <?php $color = imagecolorat($im, 50, 50); $alpha = $color >> 24; ?> It actually shifts off the first 24 bits (where 8x3 are used for each color), and returns the remaining 7 allocated bits (commonly used for alpha) fchristl
Check out this Source, it's a little funny feature showing you, for what imagecolorallocatealpha() is used: <?php $im=imagecreatetruecolor(300,300); $white=imagecolorallocate($im,255,255,255); imagefilledrectangle($im,0,0,imagesx($im),imagesy($im),$white); for($i=0;$i<256;$i=$i+10) { $col=imagecolorallocatealpha($im,$i,$i,$i,ceil(rand(0,127))); imagefilledellipse($im,$i,$i,$i,$i,$col); } header("content-type: image/png"); imagepng($im); ?> |
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