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Manage animated GIF with ImageWorkshop

The purpose of the tutorial

We will see how to work with animated GIF without losing the animation because of GD library. In this tutorial, we want to add a watermark and resize the animated GIF.

Original animated GIF with incredible Jim CarreyThe edited animated GIF

" Illustations: Jim Carrey working on ImageWorkshop... "

GD & the GIF format

GD library is not able to work with animated GIF without breaking them. In fact, a GIF is a compression of multiple images, and GD just use the first of them !

How to proceed so ?

This is simple: we will extract all the images (frames) of the GIF, then we will manage them (resizing, watermarking...), and finally we will re-generate the initial GIF with the edited frames !

Prerequisite

To perform this, we will use 2 libraries I made specially for that:


1 - Test the image format

To avoid bugs, we first have to check if the image is an animated GIF:

$gifPath = '/folder/images/pic.gif'; // Your animated GIF path

if (GifFrameExtractor::isAnimatedGif($gifPath)) { // check this is an animated GIF
    
    // All the following code will be placed here...
}
2 - Extract the frames
// Extractions of the GIF frames and their durations
$gfe = new GifFrameExtractor();
$frames = $gfe->extract($gifPath);

All the frames are now contained in the $frames array.

3 - Initializing our watermark layer
// Initialization of the watermark layer
$watermarkLayer = ImageWorkshop::initFromPath('/folder/images/watermark.jpg');
4 - Resize and watermark all the frames
$retouchedFrames = array();

// For each frame, we add a watermark and we resize it
foreach ($frames as $frame) {
	
    // Initialization of the frame as a layer
	$frameLayer = ImageWorkshop::initFromResourceVar($frame['image']);
	
	$frameLayer->resizeInPixel(350, null, true); // Resizing
	$frameLayer->addLayerOnTop($watermark, 20, 20, 'LB'); // Watermarking
	
	$retouchedFrames[] = $frameLayer->getResult();
}

All of the edited frames are now in the $retouchedFrames array ! Now it's time to create a new GIF with them...

5 - Creation of the GIF
// Then we re-generate the GIF
$gc = new GifCreator();
$gc->create($retouchedFrames, $gfe->getFrameDurations(), 0);

GifCreator::create() expect in first param an array of images, in second parameter all the frame durations (extract previously) and the last is to choose the loop number of your GIF (give 0 for infinite loop).

6 - Saving the result
// And now save it !
file_put_contents('/folder/images/newgif.gif', $gc->getGif());

GifCreator generates the string source code of your GIF, you can save the string in a new file thanks to file_put_contents() !

All the code of the tutorial:
$gifPath = '/folder/images/pic.gif'; // Your animated GIF path

if (GifFrameExtractor::isAnimatedGif($gifPath)) { // check this is an animated GIF
    
    // Extractions of the GIF frames and their durations
    $gfe = new GifFrameExtractor();
    $frames = $gfe->extract($gifPath);
    
    // Initialization of the watermark layer
    $watermarkLayer = ImageWorkshop::initFromPath('/folder/images/watermark.jpg');
    
    $retouchedFrames = array();

    // For each frame, we add a watermark and we resize it
    foreach ($frames as $frame) {
    	
        // Initialization of the frame as a layer
    	$frameLayer = ImageWorkshop::initFromResourceVar($frame['image']);
    	
    	$frameLayer->resizeInPixel(350, null, true); // Resizing
    	$frameLayer->addLayerOnTop($watermark, 20, 20, 'LB'); // Watermarking
    	
    	$retouchedFrames[] = $frameLayer->getResult();
    }
    
    // Then we re-generate the GIF
    $gc = new GifCreator();
    $gc->create($retouchedFrames, $gfe->getFrameDurations(), 0);
    
    // And now save it !
    file_put_contents('/folder/images/newgif.gif', $gc->getGif());
}

Feel free to crop, resize, change the opacity, etc, of your animated GIF ;)

Known issues

Sometimes, the edited GIF can be outputted with bad colors or even lines... Try to give a background color (or change it) with getResult('ffffff') method. This is because tranparent backgrounds can display some bugs (I'm working on ImageWorkshop to fix it).