How to Convert PNG to JPG with PHP Preserving Quality

Many websites prefer JPG images due to their reduced file size without compromising visual quality. If you have a collection of PNG files and need to convert them to JPG using PHP, here's a comprehensive guide:

PHP Functions and Libraries for PNG to JPG Conversion

PHP offers several functions and libraries that efficiently handle image manipulation.

imagecreatefrompng(): Reads a PNG file and creates an image resource.
imagejpeg(): Outputs a JPG image from an image resource.
imagecopy(): Copies a portion of one image onto another.
imagedestroy(): Frees memory associated with an image resource.

Conversion Code Snippet

To safely convert PNG to JPG with transparency in white, follow these steps:

1. Load the PNG image using imagecreatefrompng().
2. Create a true color background image filled with white using imagecreatetruecolor() and imagefill().
3. Enable alpha blending to preserve transparency with imagealphablending().
4. Copy the PNG image onto the background image using imagecopy().
5. Destroy the original PNG image resource using imagedestroy().
6. Set the desired image quality (0-100) for the JPG file.
7. Output the JPG image using imagejpeg().
8. Destroy the background image resource using imagedestroy().

$image = imagecreatefrompng($filePath);
$bg = imagecreatetruecolor(imagesx($image), imagesy($image));
imagefill($bg, 0, 0, imagecolorallocate($bg, 255, 255, 255));
imagealphablending($bg, TRUE);
imagecopy($bg, $image, 0, 0, 0, 0, imagesx($image), imagesy($image));
imagedestroy($image);
$quality = 50; // 0 = worst / smaller file, 100 = better / bigger file
imagejpeg($bg, $filePath . ".jpg", $quality);
imagedestroy($bg);