imagecolortransparent

(PHP 4, PHP 5)

imagecolortransparent — Define a color as transparent

Description

int imagecolortransparent ( resource $image [, int $color ] )

Sets the transparent color in the given image .

Parameters

image: An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
color: A color identifier created with imagecolorallocate().

Return Values

The identifier of the new (or current, if none is specified) transparent color is returned.

Examples

Example #1 imagecolortransparent() example

 <?php
// Create a 55x30 image
$im = imagecreatetruecolor(55, 30);
$red = imagecolorallocate($im, 255, 0, 0);
$black = imagecolorallocate($im, 0, 0, 0);

// Make the background transparent
imagecolortransparent($im, $black);

// Draw a red rectangle
imagefilledrectangle($im, 4, 4, 50, 25, $red);

// Save the image
imagepng($im, './imagecolortransparent.png');
imagedestroy($im);
?>

The above example will output something similar to:

Notes

Note: Transparency is copied only with imagecopymerge() and true color images, not with imagecopy() or pallete images.

Note: The transparent color is a property of the image, transparency is not a property of the color. Once you have set a color to be the transparent color, any regions of the image in that color that were drawn previously will be transparent.