PHP创建的水印看起来很奇怪

Question

我有脚本添加水印(PNG，透明)到图像(JPG)。在某种程度上，水印会改变颜色并使其不透明。这是我用来添加水印的代码：

$im = imagecreatefromjpeg('../../pics/'.$ran.'_large.jpg');
$stamp = imagecreatefrompng('a.png');

$marge_right = 10;
$marge_bottom = 10;
$sx = imagesx($stamp);
$sy = imagesy($stamp);

imagecopymerge($im, $stamp, imagesx($im) - $sx - $marge_right, imagesy($im) - $sy - $marge_bottom, 0, 0, imagesx($stamp), imagesy($stamp), 70);

// Save the image to file and free memory
imagejpeg($im, '../../pics/'.$ran.'_large.jpg');
imagedestroy($im);

Image with watermark after PHP generates it (wrong way)

Answer 1

感谢你们的帮助- I found answer in this site

$im = imagecreatefromjpeg('../../pics/'.$ran.'_large.jpg');
$stamp = imagecreatefrompng('a.png');

imagealphablending($im, true);

$marge_right = 10;
$marge_bottom = 10;

$sx = imagesx($stamp);
$sy = imagesy($stamp);

$offset = 10;

imagecopy($im, $stamp, imagesx($im) - imagesx($stamp) - $offset, imagesy($im) - imagesy($stamp) - $offset, 0, 0, imagesx($stamp), imagesy($stamp));
// Save the image to file and free memory
imagejpeg($im, '../../pics/'.$ran.'_large.jpg');
imagedestroy($im);

Answer 2

您的输出图像格式为jpeg。Jpeg不支持透明。将输出格式更改为png。

也建议你使用图像魔法。Gd是非常原始的。

Answer 3

当从PNG创建带有alpha图的PNG图像时，不要忘记这些函数：

imagealphablending($stamp,false);
imagesavealpha($stamp,true);

看看有没有什么不同？