用白色PHP GD替换透明bg

Question

I have an image in php generated like so:

$base = imagecreatefromstring(file_get_contents($_GET['imgSRC']));
imagepalettetotruecolor($base);
$background = imagecolorallocate($base, 0, 0, 0);
imagecolortransparent($base, $background);
imagealphablending($base, false);
imagesavealpha($base, true);

The image has a transparent background, I would like to replace any transparent pixels with white. What is the cleanest way to do this?

Answer 1

Creating a solid image and copying the transparent image over it worked for me:

class Solid {
    static function white() {
        return new self(255, 255, 255);
    }

    function __construct($red, $green, $blue) {
        $this->red = $red;
        $this->green = $green;
        $this->blue = $blue;
    }

    function under($pic) {
        $w = imagesx($pic);
        $h = imagesy($pic);

        $buffer = imagecreatetruecolor($w, $h);
        imagefilledrectangle($buffer, 0, 0, $w, $h,
            imagecolorallocate($buffer, $this->red, $this->green, $this->blue));

        imagecopy($buffer, $pic, 0, 0, 0, 0, $w, $h);

        return $buffer;
    }
}

This is how I use it:

$solid_picture = Solid::white()->under($transparent_picture);

In case your picture has an alpha channel, consider using imagecopymerge() instead of imagecopy .