Using GD in PHP, how can I make a transparent PNG watermark on PNG and GIF files ? (JPG files work fine)
I have an image (let's call it original image) on which I want to watermark another image (let's call it logo).
The logo is a transparent PNG, whereas the original image can be png, jpg, or gif. I have the following code: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开发者_高级运维;
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);
}
This code works good (good = keep the transparency of the logo) only when the original image is a JPG file.
When the original file is a GIF or PNG, the logo has a solid white background, meaning the transparency is not working.Why ? What do I need to change so it'll work ?
ThanksUPDATE:
Here is my recoded version: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 does not support using two images with alpha channels. take a look at imagecopymerge.
http://php.net/manual/en/function.imagecopymerge.php
There are plenty examples in the user comments sections, and a finished implementation for what you want:
http://www.php.net/manual/en/function.imagecopymerge.php#92787
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