WaterMarking在gif图像上

Question

所以我正在为Gif图像上的png图像加水印。我的代码是：

<?php
// Load the stamp and the photo to apply the watermark to
$stamp = imagecreatefrompng('add_item.png');// watermark image
$im = imagecreatefromjpeg('gif_image.gif');// source image
$image_path = "/opt/lampp/htdocs/my/Harshal/watermarking/".time().".png";

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

// Copy the stamp image onto our photo using the margin offsets and the photo 
// width to calculate positioning of the stamp. 
imagecopy($im, $stamp, imagesx($im) - $sx - $marge_right, imagesy($im) - $sy - $marge_bottom, 0, 0, imagesx($stamp), imagesy($stamp));

// Output and free memory
//header('Content-type: image/png');
imagepng($im,$image_path);
imagedestroy($im);
?>

我的代码工作正常并且在gif图像上为png图像添加水印但问题是： 水印png图像后面有白色背景，而其他图像则没有透明。

你们能告诉我为什么只有gif图像有问题吗？

查看生成的图像。

我知道Gif是许多图像的组合，但有没有任何解决方案可以让图像具有正常的行为。 我也看到了一些在线水印工具，但它们也有同样的问题。

Answer 1

您可以将gif转换为真彩色图像。试试这个：

<?php
// Load the stamp and the photo to apply the watermark to
$stamp = imagecreatefrompng('add_item.png');// watermark image
$im = imagecreatefromgif('gif_image.gif');// source image
$image_path = "/opt/lampp/htdocs/my/Harshal/watermarking/".time().".png";

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

// Convert gif to a true color image
$tmp = imagecreatetruecolor(imagesx($im), imagesy($im));
$bg = imagecolorallocate($tmp, 255, 255, 255);
imagefill($tmp, 0, 0, $bg);
imagecopy($tmp, $im, 0, 0, 0, 0, imagesx($im), imagesy($im));
$im = $tmp;

// Copy the stamp image onto our photo using the margin offsets and the photo 
// width to calculate positioning of the stamp. 
imagecopy($im, $stamp, imagesx($im) - $sx - $marge_right, imagesy($im) - $sy - $marge_bottom, 0, 0, imagesx($stamp), imagesy($stamp));

// Output and free memory
//header('Content-type: image/png');
imagepng($im,$image_path);
imagedestroy($im);