imagecolormatch

    (PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

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

    Description

    imagecolormatch(GdImage $image1, GdImage $image2): bool

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

    Parameters

    image1

    A truecolor image object.

    image2

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

    Return Values

    Returns true on success or false on failure.

    Changelog

    Version Description
    8.0.0 image1 and image2 expect GdImage instances now; previously, resources were expected.

    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();
    $colors[] = imagecolorallocate($im2, 255, 36, 74);
    $colors[] = imagecolorallocate($im2, 40, 0, 240);
    $colors[] = imagecolorallocate($im2, 82, 100, 255);
    $colors[] = imagecolorallocate($im2, 84, 63, 44);

    // Match these colors with the true color image
    imagecolormatch($im1, $im2);

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

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    User Contributed Notes 3 notes

    up
    2
    gk at karko dot net
    14 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
    up
    1
    albriNOght at anSPAMre dot net
    18 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.
    up
    0
    Samantha
    20 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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