thinkphp在为图片添加png水印不足的处理

thinkphp在为图片加水印的时候。如果水印图片是png图片，透明度处理很不理想，与是做以下处理

在Image.class.php中新增

static function imagecopymerge_alpha($dst_im, $src_im, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h, $pct){
        $opacity=$pct;
        // getting the watermark width
        $w = imagesx($src_im);
        // getting the watermark height
        $h = imagesy($src_im);

        // creating a cut resource
        $cut = imagecreatetruecolor($src_w, $src_h);
        // copying that section of the background to the cut
        imagecopy($cut, $dst_im, 0, 0, $dst_x, $dst_y, $src_w, $src_h);
        // inverting the opacity
        //$opacity = 100 - $opacity;

        // placing the watermark now
        imagecopy($cut, $src_im, 0, 0, $src_x, $src_y, $src_w, $src_h);
        imagecopymerge($dst_im, $cut, $dst_x, $dst_y, $src_x, $src_y, $src_w, $src_h, $opacity);
    }

然后在water方法中把原来的替换就ok，替换方法如下：

//生成混合图像(原来系统中的,注释掉)

//imagecopymerge($sImage, $wImage, $posX, $posY, 0, 0, $wInfo['width'], $wInfo['height'], $alpha);
//新加===================================================================
self::imagecopymerge_alpha($sImage, $wImage, $posX, $posY, 0, 0, $wInfo['width'], $wInfo['height'], $alpha);