PHP: Resize image - preserve ratio of width and height

resize_image.php

/**
 * Resize image - preserve ratio of width and height.
 * @param string $sourceImage path to source JPEG image
 * @param string $targetImage path to final JPEG image file
 * @param int $maxWidth maximum width of final image (value 0 - width is optional)
 * @param int $maxHeight maximum height of final image (value 0 - height is optional)
 * @param int $quality quality of final image (0-100)
 * @return bool
 */
function resizeImage($sourceImage, $targetImage, $maxWidth, $maxHeight, $quality = 80)
{
    // Obtain image from given source file.
    if (!$image = @imagecreatefromjpeg($sourceImage))
    {
        return false;
    }

    // Get dimensions of source image.
    list($origWidth, $origHeight) = getimagesize($sourceImage);

    if ($maxWidth == 0)
    {
        $maxWidth  = $origWidth;
    }

    if ($maxHeight == 0)
    {
        $maxHeight = $origHeight;
    }

    // Calculate ratio of desired maximum sizes and original sizes.
    $widthRatio = $maxWidth / $origWidth;
    $heightRatio = $maxHeight / $origHeight;

    // Ratio used for calculating new image dimensions.
    $ratio = min($widthRatio, $heightRatio);

    // Calculate new image dimensions.
    $newWidth  = (int)$origWidth  * $ratio;
    $newHeight = (int)$origHeight * $ratio;

    // Create final image with new dimensions.
    $newImage = imagecreatetruecolor($newWidth, $newHeight);
    imagecopyresampled($newImage, $image, 0, 0, 0, 0, $newWidth, $newHeight, $origWidth, $origHeight);
    imagejpeg($newImage, $targetImage, $quality);

    // Free up the memory.
    imagedestroy($image);
    imagedestroy($newImage);

    return true;
}

/**
 * Example
 * resizeImage('image.jpg', 'resized.jpg', 200, 200);
 */
 

Everything works fine except PNG transparency. I am getting a black background on all PNGs.

work awesome!