imagecolorallocatealpha — Assign color and transparency to an image.
int imagecolorallocatealpha ( resource $image , int $red , int $green , int $blue , int $alpha )
imagecolorallocatealpha() behaves the same as imagecolorallocate(), but with an additional transparency parameter, alpha, whose values range from 0 to 127. 0 means fully opaque and 127 means fully transparent.
Returns FALSE if allocation fails.
Note: This function requires GD 2.0.1 or higher (2.0.28 and higher recommended).
<?php$size = 300;$image=imagecreatetruecolor($size, $size);//Draw a box with a white background and a black border$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;//use alpha Value assign some color $yellow = imagecolorallocatealpha($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, $blue);//Don’t forget to output the correct header! header('Content-type: image/png');//The final output result imagepng($image);imagedestroy($image);?>The picture of the output result of the above example is as follows:
imagecolorallocate() assigns a color to an image.
imagecolordeallocate() Deallocates an image color.