[英]Merging (watermark) a jpg with png while resizing the png in PHP GD
[英]Using GD in PHP, how can I make a transparent PNG watermark on PNG and GIF files ? (JPG files work fine)
我有一个图像(让我们称之为原始图像 ),我想在其上为另一个图像添加水印(让我们称之为徽标 )。
徽标是透明的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);
}
仅当原始图像是JPG文件时,此代码才能正常工作(良好=保持徽标的透明度)。
当原始文件是GIF或PNG时,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起作用?
谢谢
更新:
这是我的重新编码版本:
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);
}
imagecopy不支持使用带有Alpha通道的两个图像。 看看imagecopymerge。
http://php.net/manual/en/function.imagecopymerge.php
用户注释部分有很多示例,并且您可以根据需要完成实现:
http://www.php.net/manual/en/function.imagecopymerge.php#92787
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