Define a color as transparent

# imagecolortransparent

(PHP 4, PHP 5, PHP 7, PHP 8)

imagecolortransparent — Define a color as transparent

### Description

imagecolortransparent(GdImage `$image`, ?int `$color` = `null`): int

Gets or sets the transparent color in the given `image`.

### Parameters

`image`

  A GdImage object, 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 `null`, and the image has no transparent color, the returned identifier will be `-1`.

### Changelog

Version | Description
--- | ---
8.0.0 | `image` expects a GdImage instance now; previously, a valid `gd` resource was expected.
8.0.0 | `color` is now nullable.

### 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');
?>`

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.

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