PHP 7.1.1 Released


(PHP 4 >= 4.3.0, PHP 5, PHP 7)

imagecolormatchMakes the colors of the palette version of an image more closely match the true color version


bool imagecolormatch ( resource $image1 , resource $image2 )

Makes the colors of the palette version of an image more closely match the true color version.



A truecolor image link resource.


A palette image link resource pointing to an image that has the same size as image1.

Return Values

Returns TRUE on success or FALSE on failure.


Example #1 imagecolormatch() example

// Setup the true color and palette images
$im1 imagecreatefrompng('./gdlogo.png');
$im2 imagecreate(imagesx($im1), imagesy($im1));

// Add some colors to $im2
$colors   = Array();
$colors[] = imagecolorallocate($im22553674);
$colors[] = imagecolorallocate($im2400240);
$colors[] = imagecolorallocate($im282100255);
$colors[] = imagecolorallocate($im2846344);

// Match these colors with the true color image

// Free from memory

See Also

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User Contributed Notes 3 notes

gk at karko dot net
6 years ago
Those that have Ubuntu servers note, that this function is added in PHP's GD library fork and is not available by default in Ubuntu php5-gd package.

Here's how-to install the PHP GD version:
albriNOght at anSPAMre dot net
11 years ago
This function appears to work by changing the values of the colors of the paletted image -- no good if you're trying to force the resultant image to stick with certain pre-defined color values.
12 years ago
This function is a godsend! It works exactly as documented.

I'm working on an application where I need to take a transparent GIF, matte the GIF on a user defined background color, and finally scale the GIF based on a user defined %.

The only way I could get this to work so that the final image was high quality, ie: no jagged edges, and a smooth scale, was to convert the GIF to a JPG, and then copy the JPG into a new GIF image like this:

// open transparent gif
$GIFimg = imagecreatefromgif($file_path);

// create jpg image
$JPGimg = imagecreatetruecolor($width, $height);

// copy GIF to JPG
imagecopy($JPGimg, $GIFimg, 0, 0, 0, 0, $width, $height);

// create a true color image
$JPGscaled = imagecreatetruecolor($n_width, $n_height);

// scale the new JPG using the truecolor image
imagecopyresampled($JPGscaled, $JPGimg, 0, 0, 0, 0, $new_width, $new_height, $width, $height);

// create final GIF image
$GIFfinal = imagecreate($n_width, $n_height);

// copy the scaled JPG back to a GIF
imagecopymerge($GIFfinal, $JPGscaled, 0, 0, 0, 0, $n_width, $n_height, 100);

This worked great except the final step, copying the JPG to a GIF. If the JPG had too many colors, the function would index the colors to make it a palette image. So what would end up happening is the final image contained INCORRECT colors.

Adding this one line at the bottom of the code fixed everything.

imagecolormatch($JPGscaled, $GIFfinal);

I hope this helps anyone who is converting images back and forth and dealing with palette issues and color correction. Also, be aware that the above code is a sample and will not work by copying and pasting.
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