What are some common pitfalls when using PHP GD for watermarking images?

One common pitfall when using PHP GD for watermarking images is not setting the correct transparency for the watermark, resulting in a watermark that appears opaque and obstructive. To solve this issue, make sure to set the correct alpha channel value when creating the watermark image using imagecopymerge. 

// Load the main image
$mainImage = imagecreatefromjpeg('main_image.jpg');

// Load the watermark image
$watermark = imagecreatefrompng('watermark.png');

// Set the transparency level for the watermark
imagealphablending($watermark, false);
imagesavealpha($watermark, true);

// Get the dimensions of the watermark image
$watermarkWidth = imagesx($watermark);
$watermarkHeight = imagesy($watermark);

// Calculate the position to place the watermark on the main image
$positionX = imagesx($mainImage) - $watermarkWidth - 10;
$positionY = imagesy($mainImage) - $watermarkHeight - 10;

// Merge the watermark onto the main image
imagecopymerge($mainImage, $watermark, $positionX, $positionY, 0, 0, $watermarkWidth, $watermarkHeight, 50);

// Output the watermarked image
header('Content-Type: image/jpeg');
imagejpeg($mainImage);

// Free up memory
imagedestroy($mainImage);
imagedestroy($watermark);

Keywords

PHP GD watermarking images transparency positioning

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