How to get GIF transparency color for saving with GD?

问题

My GD wrapper works like charm with JPEG and PNG images, however when using GIF image the resulting image loses transparency.

Further search suggests i have to use imagecolortransparent (sets the transparent color) after getting color identifier with:

imagecolorallocate (resource $image , int $red , int $green , int $blue).

So question is: how can i get original transparecy color (RGB)?

回答1:

Assuming that the GIF image is loaded into resource $image... try the following

$index_of_transparent_colour = imagecolortransparent($image);
if($index_of_transparent_colour != -1) {
    $actual_transparent_colour = imagecolorsforindex($image,$index_of_transparent_colour);
}

Should be able to access the actual RGB values from

$actual_transparent_colour['red']
$actual_transparent_colour['green'] 
$actual_transparent_colour['blue']

Hope this helps :)

Love to all :)

来源：https://stackoverflow.com/questions/8528903/how-to-get-gif-transparency-color-for-saving-with-gd