What are the potential reasons for transparent areas being replaced with black color when using PHP to overlay PNG on JPG images?

When overlaying a PNG image with transparent areas on top of a JPG image using PHP, the transparent areas may be replaced with black color due to the way JPG images handle transparency. To solve this issue, you can use imagecopymerge() function in PHP to overlay the PNG image onto the JPG image while preserving transparency. 

$jpgImage = imagecreatefromjpeg('background.jpg');
$pngImage = imagecreatefrompng('overlay.png');

imagealphablending($jpgImage, true);
imagesavealpha($jpgImage, true);

$width = imagesx($pngImage);
$height = imagesy($pngImage);

imagecopymerge($jpgImage, $pngImage, 0, 0, 0, 0, $width, $height, 100);

header('Content-Type: image/jpeg');
imagejpeg($jpgImage);

imagedestroy($jpgImage);
imagedestroy($pngImage);

Keywords

PHP PNG JPG transparency image overlay

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