imagecolormatch

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

imagecolormatch — 使一个图像中调色板版本的颜色与真彩色版本更能匹配

说明

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

使一个图像中调色板版本的颜色与真彩色版本更能匹配。

参数

image1: 真彩色图像连接资源。
image2: 必须是调色板图像，而且和 image1 的大小必须相同。

返回值

成功时返回 true，或者在失败时返回 false。

范例

Example #1 imagecolormatch() 例子


<?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);
?>

注释

参见

imagecreatetruecolor() - 新建一个真彩色图像

User Contributed Notes

gk at karko dot net 28-Jun-2010 09:42


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

albriNOght at anSPAMre dot net 12-Dec-2005 09:22


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.

Samantha 08-Feb-2004 07:14


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.