PHP: imagecolormatch

Description

bool imagecolormatch ( resource image1, resource image2 )

Ostrzeżenie

Ta funkcja jest obecnie nieudokumentowana, dostępna jest jedynie lista jej argumentów.

image1 must be Truecolor, image2 must be Palette, and both image1 and image2 must be the same size.

Zwraca TRUE w przypadku sukcesu, FALSE w przypadku porażki.

Notatka: Ta funkcja jest dostępna tylko jeśli PHP zostało skompilowane z dołączoną wersją biblioteki GD.

Notatka: Fa funkcja wymaga GD 2.0.1 lub nowszego.

See also imagecreatetruecolor().


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.

imagecolormatch

Description

User Contributed Notes