IMAGECOLORALLOCATEALPHA(3) 1 IMAGECOLORALLOCATEALPHA(3)
imagecolorallocatealpha - Allocate a color for an image
SYNOPSIS
int imagecolorallocatealpha (resource $image, int $red, int $green, int $blue, int $alpha)
DESCRIPTION
imagecolorallocatealpha(3) behaves identically to imagecolorallocate(3) with the addition of the transparency parameter $alpha.
PARAMETERS
o $
image -An image resource, returned by one of the image creation functions, such as imagecreatetruecolor(3).
o $red
-Value of red component.
o $green
-Value of green component.
o $blue
-Value of blue component.
o $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. Previ- |
| | ously -1 was returned. |
| | |
+--------+---------------------------------------------------+
EXAMPLES
Example #1
Example of using imagecolorallocatealpha(3)
<?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:[NOT DISPLAYABLE MEDIA]Output of example : Example of using imagecolorallocateal-
pha()
NOTES
Note
This function requires GD 2.0.1 or later (2.0.28 or later is recommended).
SEE ALSO
imagecolorallocate(3), imagecolordeallocate(3).
PHP Documentation Group IMAGECOLORALLOCATEALPHA(3)