imagecolorallocatealpha

(PHP 4 >= 4.3.2, PHP 5, PHP 7)

imagecolorallocatealpha — Allocate a color for an image

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.

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 0 and 127. 0 indicates completely opaque while 127 indicates completely transparent.

The red, green and blue parameters are integers between 0 and 255 or hexadecimals between 0x00 and 0xFF.

Return Values

A color identifier or FALSE if the allocation failed.

Warning

This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE. Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.

Changelog

Version	Description
5.1.3	Returns FALSE if the allocation failed. Previously -1 was returned.

Examples

Example #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
?>

The above example will output something similar to: