imagecolormatch

(PHP 4 >= 4.3.0, PHP 5)

imagecolormatch — パレットイメージの色を True カラーイメージに近づける

説明

bool imagecolormatch ( resource $image1 , resource $image2 )

パレットイメージの色を True カラーイメージに近づけます。

パラメータ

image1: truecolor イメージリンクリソース。
image2: パレットイメージリンクリソース。 image1 と同じ大きさの画像をさします。

返り値

成功した場合に TRUE を、失敗した場合に FALSE を返します。

注意

注意: この関数は、PHP がバンドル版の GD ライブラリでコンパイルされている場合のみ使用可能です。

注意: この関数は、GD 2.0.1 以降を必要とします (2.0.28 以降を推奨します)。

参考

imagecreatetruecolor()

add a note User Contributed Notes
imagecolormatch

albriNOght at anSPAMre dot net
12-Dec-2005 06:22


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
09-Feb-2004 04:14


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.

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imagecolorresolve

imagecolorexactalpha

Last updated: Fri, 05 Sep 2008