我有一个图像(我们称之为原始图像)我想在另一个图像上加水印(我们称之为logo).
The logo是透明的 PNG,而原始图像可以是 png、jpg 或 gif。
我有以下代码:
function watermarkImage($originalFileContents, $originalWidth, $originalHeight) {
$logoImage = imagecreatefrompng('logo.png');
imagealphablending($logoImage, true);
$logoWidth = imagesx($logoImage);
$logoHeight = imagesy($logoImage);
$originalImage = imagecreatefromstring($originalFileContents);
$destX = $originalWidth - $logoWidth;
$destY = $originalHeight - $logoHeight;
imagecopy(
// source
$originalImage,
// destination
$logoImage,
// destination x and y
$destX, $destY,
// source x and y
0, 0,
// width and height of the area of the source to copy
$logoWidth, $logoHeight
);
imagepng($originalImage);
}
这段代码效果很好(好=保持透明度logo)仅当原始图像是一个 JPG 文件。
当。。。的时候原始文件是 GIF 或 PNG,徽标具有纯白色背景,这意味着透明度不起作用。
为什么 ?我需要改变什么才能让它发挥作用?
Thanks
UPDATE:
这是我重新编码的版本:
function generate_watermarked_image($originalFileContents, $originalWidth, $originalHeight, $paddingFromBottomRight = 0) {
$watermarkFileLocation = 'watermark.png';
$watermarkImage = imagecreatefrompng($watermarkFileLocation);
$watermarkWidth = imagesx($watermarkImage);
$watermarkHeight = imagesy($watermarkImage);
$originalImage = imagecreatefromstring($originalFileContents);
$destX = $originalWidth - $watermarkWidth - $paddingFromBottomRight;
$destY = $originalHeight - $watermarkHeight - $paddingFromBottomRight;
// creating a cut resource
$cut = imagecreatetruecolor($watermarkWidth, $watermarkHeight);
// copying that section of the background to the cut
imagecopy($cut, $originalImage, 0, 0, $destX, $destY, $watermarkWidth, $watermarkHeight);
// placing the watermark now
imagecopy($cut, $watermarkImage, 0, 0, 0, 0, $watermarkWidth, $watermarkHeight);
// merging both of the images
imagecopymerge($originalImage, $cut, $destX, $destY, 0, 0, $watermarkWidth, $watermarkHeight, 100);
}