Create thumbnails with PHP

create-thumbnail.php

<?

// Link image type to correct image loader and saver
// - makes it easier to add additional types later on
// - makes the function easier to read
const IMAGE_HANDLERS = [
    IMAGETYPE_JPEG => [
        'load' => 'imagecreatefromjpeg',
        'save' => 'imagejpeg',
        'quality' => 100
    ],
    IMAGETYPE_PNG => [
        'load' => 'imagecreatefrompng',
        'save' => 'imagepng',
        'quality' => 0
    ],
    IMAGETYPE_GIF => [
        'load' => 'imagecreatefromgif',
        'save' => 'imagegif'
    ]
];

/**
 * @param $src - a valid file location
 * @param $dest - a valid file target
 * @param $targetWidth - desired output width
 * @param $targetHeight - desired output height or null
 */
function createThumbnail($src, $dest, $targetWidth, $targetHeight = null) {

    // 1. Load the image from the given $src
    // - see if the file actually exists
    // - check if it's of a valid image type
    // - load the image resource

    // get the type of the image
    // we need the type to determine the correct loader
    $type = exif_imagetype($src);

    // if no valid type or no handler found -> exit
    if (!$type || !IMAGE_HANDLERS[$type]) {
        return null;
    }

    // load the image with the correct loader
    $image = call_user_func(IMAGE_HANDLERS[$type]['load'], $src);

    // no image found at supplied location -> exit
    if (!$image) {
        return null;
    }


    // 2. Create a thumbnail and resize the loaded $image
    // - get the image dimensions
    // - define the output size appropriately
    // - create a thumbnail based on that size
    // - set alpha transparency for GIFs and PNGs
    // - draw the final thumbnail

    // get original image width and height
    $width = imagesx($image);
    $height = imagesy($image);

    // maintain aspect ratio when no height set
    if ($targetHeight == null) {

        // get width to height ratio
        $ratio = $width / $height;

        // if is portrait
        // use ratio to scale height to fit in square
        if ($width > $height) {
            $targetHeight = floor($targetWidth / $ratio);
        }
        // if is landscape
        // use ratio to scale width to fit in square
        else {
            $targetHeight = $targetWidth;
            $targetWidth = floor($targetWidth * $ratio);
        }
    }

    // create duplicate image based on calculated target size
    $thumbnail = imagecreatetruecolor($targetWidth, $targetHeight);

    // set transparency options for GIFs and PNGs
    if ($type == IMAGETYPE_GIF || $type == IMAGETYPE_PNG) {

        // make image transparent
        imagecolortransparent(
            $thumbnail,
            imagecolorallocate($thumbnail, 0, 0, 0)
        );

        // additional settings for PNGs
        if ($type == IMAGETYPE_PNG) {
            imagealphablending($thumbnail, false);
            imagesavealpha($thumbnail, true);
        }
    }

    // copy entire source image to duplicate image and resize
    imagecopyresampled(
        $thumbnail,
        $image,
        0, 0, 0, 0,
        $targetWidth, $targetHeight,
        $width, $height
    );


    // 3. Save the $thumbnail to disk
    // - call the correct save method
    // - set the correct quality level

    // save the duplicate version of the image to disk
    return call_user_func(
        IMAGE_HANDLERS[$type]['save'],
        $thumbnail,
        $dest,
        IMAGE_HANDLERS[$type]['quality']
    );
}

Thanks a lot for this!
On my page (https://www.pollisoft.se), is use the same thumbnail size for all image size and aspect ratios. With the following change/addition (the else statement) to your script, I avoided thumbnail image distortion when sourceRatio doesn't equal targetRatio. Feel free to include if you want.

`// maintain aspect ratio when no height set
if ($targetHeight == null) {

	$startX = 0;
	$startY = 0;
	$src_w = width;
	$src_h = height;
	
    // get width to height ratio
    $ratio = $width / $height;

    // if is portrait
    // use ratio to scale height to fit in square
    if ($width > $height) {
        $targetHeight = floor($targetWidth / $ratio);
    }
    // if is landscape
    // use ratio to scale width to fit in square
    else {
        $targetHeight = $targetWidth;
        $targetWidth = floor($targetWidth * $ratio);
    }
} else {
	// Calculate starting positions and copy area 
	// to not distort the thumbnail image ratio.
	// get width to height ratio
	$ratio = $width / $height;
	$targetRatio = $targetWidth / $targetHeight;
	$combinedRatio = $ratio / $targetRatio;

	// Cut X wise in source to avoid thumb image distortion
	if ($combinedRatio >= 1) {
		$thumbRatio = $height / $targetHeight;
		$startX = ($width - ($thumbRatio * $targetWidth)) / 2;
		$src_w = ($thumbRatio * $targetWidth);
		$startY = 0;
		$src_h = $height;
	}
	// Cut Y wise in source to avoid thumb image distortion
	else {
		$thumbRatio = $width / $targetWidth;
		$startY = ($height - ($thumbRatio * $targetHeight)) / 2;
		$src_h = ($thumbRatio * $targetHeight);
		$startX = 0;
		$src_w = $width;
	}
}`

Hi
I am getting error for gif images : imagegif() expects at most 2 arguments, 3 given
Thanks