imagecolorstotal
imageconvolution
GD and Image Functions
PHP Manual

# 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. If `color` is not specified, and the image has no transparent color, the returned identifier will be -1.

### 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.