imagecolormatch

(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

Description

bool imagecolormatch ( resource $image1 , resource $image2 )

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

Parameters

image1

A truecolor image link resource.

image2

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.

Examples

Example #1 imagecolormatch() example

<?php
// 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
imagecolormatch($im1$im2);

// Free from memory
imagedestroy($im1);
imagedestroy($im2);
?>

Notes

Note: This function requires GD 2.0.1 or later (2.0.28 or later is recommended).

See Also

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User Contributed Notes 3 notes

up
1
gk at karko dot net
235 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: http://preview.tinyurl.com/yel4r7t
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1
albriNOght at anSPAMre dot net
240 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.
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-1
Samantha
242 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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