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Animated GIF files become not animated after resizing in Sitecore

Maintaining websites in Sitecore helps you discover interesting issues. In this blog, we discuss one such issue :)

The Problem

We all know that Sitecore has the ability to resize images based on the query parameters that are supplied in a media item's URL. You must have already figured out that animated GIF files become not animated after resizing in Sitecore (it is in this blog's title itself). 

Wondering why it happens? According to Sitecore in KB1001735  - 

There is no built-in .NET functionality to resize a GIF file and keep its properties (for example, the delay between frames). In this case, only the first frame of the file is displayed. As a result, the animated GIF file might become not animated after resizing it using Sitecore.  

What this means is if you have a GIF like this - 


and if you want to resize it in Sitecore, it will appear like this - 


Sitecore has suggested a fix for it in the KB article which skips resizing of GIF files to prevent GIF files from becoming non-animated. If this solution suits you, you may go for it. But in our case, we did not want to loose the performance benefits which come with resized GIFs. So, we decided to find a way to resize the GIF files.

The Solution

I started understanding the processor mentioned in KB article which is - Sitecore.Resources.Media.ResizeProcessor, Sitecore.Kernel

While analyzing it, I was able to find that the below line is responsible for the transformation or resizing - 
Stream stream = this.MediaManager.Effects.TransformImageStream(mediaStream.Stream, transformationOptions, imageFormat);

This TransformImageStream() method goes to Sitecore.Resources.Media.ImageEffects which further calls Sitecore.Resources.Media.ResizeImageStream() method as in below line - 
return new ImageEffectsResize().ResizeImageStream(inputStream, options, outputFormat);

This ResizeImageStream() contains the code responsible for running the logics before resizing the image. This looked like a useful method to me which can be copied over into my processor. This method contains below line which actually resizes the image - 
Bitmap bitmap2 = resizer.Resize(bitmap1, resizeOptions, outputFormat)

This is where we want to add our logic to resize the GIF files.

If you are wondering, this is how resizer resizes a GIF - 
private Bitmap ResizeGif(Bitmap image, Size size, bool preserveResolution)
    {
      return image.Size == size ? image : new ThumbMaker(image).ResizeToGif(size, preserveResolution);
    }

Now, we needed a way to resize a GIF images. Little browsing suggested that it is possible to resize GIF images using a third party library like Magick.Net. It can be installed as a NuGet in the project.

I started testing the Magick.Net NuGet for GIF resizing in Sitecore and after a few exceptions, I was able to resize a GIF image successfully in Sitecore. Here is the code from the proof of concept -

Disclaimer - This is just a proof of concept work and it should be properly refined before deploying to production

Custom Processor code -
using Sitecore.Abstractions;
using Sitecore.Diagnostics;
using scResources = global::Sitecore.Resources.Media;
using Sitecore.Resources.Media;
using Sitecore.ImageLib;
using Sitecore.IO;
using Sitecore.Configuration;
using ImageMagick;
using System;
using System.IO;
using System.Drawing.Imaging;
using System.Drawing;

namespace <Your Namespace>
{
    public class GifResizeProcessor : scResources.ResizeProcessor
    {
        public GifResizeProcessor(BaseMediaManager mediaManager, BaseLog log) : base(mediaManager, log)
        {
        }

        public new void Process(GetMediaStreamPipelineArgs args)
        {
            Assert.ArgumentNotNull(args, "args");
            if (!string.Equals(args.MediaData.MimeType, "image/gif", StringComparison.OrdinalIgnoreCase))
            {
                base.Process(args);
            }
            else
            {
                MediaStream outputStream = args.OutputStream;
                string extension = args.MediaData.Extension;
                MediaStream mediaStream = outputStream;
                TransformationOptions transformationOptions = args.Options.GetTransformationOptions();
                ImageFormat imageFormat = this.MediaManager.Config.GetImageFormat(extension, (ImageFormat)null);
                Stream stream = ResizeImageStream(mediaStream.Stream, transformationOptions, imageFormat);
                args.OutputStream = new MediaStream(stream, extension, mediaStream.MediaItem);
            }
        }

        public Stream ResizeImageStream(
      Stream inputStream,
      TransformationOptions options,
      ImageFormat outputFormat)
        {
            Assert.ArgumentNotNull((object)inputStream, nameof(inputStream));
            Assert.ArgumentNotNull((object)options, nameof(options));
            Assert.ArgumentNotNull((object)outputFormat, nameof(outputFormat));
            ResizeOptions resizeOptions = GetResizeOptions(options);

            if (resizeOptions.IsEmpty)
                return inputStream;

            if (inputStream.Length > Settings.Media.MaxSizeInMemory)
            {
                Tracer.Error((object)"Could not resize image stream as it was larger than the maximum size allowed for memory processing.");
                return (Stream)null;
            }

            Resizer resizer = new Resizer();
            MemoryStream memoryStream = new MemoryStream();
            FileUtil.CopyStream(inputStream, (Stream)memoryStream, 8192);
            inputStream.Close();
            memoryStream.Seek(0L, SeekOrigin.Begin);

            // Save the result            
            using (Bitmap bitmap1 = new Bitmap((Stream)memoryStream))
            {
                bool proportionsAreSaved;
                Size frameSize = resizer.GetFrameSize(bitmap1, resizeOptions, out proportionsAreSaved);
                Size imageSize = GetImageSize(bitmap1, frameSize, resizeOptions, proportionsAreSaved);
                if (bitmap1.Size.Equals((object)frameSize))
                {
                    memoryStream.Seek(0L, SeekOrigin.Begin);
                    return (Stream)memoryStream;
                }

                memoryStream.Seek(0L, SeekOrigin.Begin);
                //here resize using magick
                var readSettings = new MagickReadSettings() { Format = MagickFormat.Gif };
                //var image = new magickimage(svgstream, readsettings);
                using (var collection = new MagickImageCollection(memoryStream, readSettings))
                {
                    collection.Coalesce();

                    // Resize each image in the collection to the width
                    foreach (var image in collection)
                    {
                        image.Resize(imageSize.Width, imageSize.Height);
                    }
                    MemoryStream resizedMemoryStream = new MemoryStream();
                    collection.Write(resizedMemoryStream);
                    resizedMemoryStream.Seek(0L, SeekOrigin.Begin);
                    memoryStream.Close();
                    return (Stream)resizedMemoryStream;
                }
            }
        }
///////////////ALL METHODS BELOW THIS POINT HAVE BEEN JUST COPIED OVER FROM SITECORE DLLS TO MAKE THIS CODE WORK. NO CUSTOMIZATION DONE IN THERE/////////////////////
        private static ResizeOptions GetResizeOptions(TransformationOptions options)
        {
            return new ResizeOptions()
            {
                AllowStretch = options.AllowStretch,
                BackgroundColor = options.BackgroundColor,
                IgnoreAspectRatio = options.IgnoreAspectRatio,
                MaxSize = options.MaxSize,
                Scale = options.Scale,
                Size = options.Size,
                PreserveResolution = options.PreserveResolution,
                CompositingMode = options.CompositingMode,
                InterpolationMode = options.InterpolationMode,
                PixelOffsetMode = options.PixelOffsetMode
            };
        }

        private Size GetImageSize(
      Bitmap image,
      Size frameSize,
      ResizeOptions options,
      bool proportionsAreSaved)
        {
            if (proportionsAreSaved || options.IgnoreAspectRatio)
                return frameSize;
            float val1 = (float)frameSize.Width / (float)image.Width;
            float val2 = (float)frameSize.Height / (float)image.Height;
            float amount = Math.Min(val1, val2);
            if (!options.AllowStretch && (double)amount > 1.0)
                return new Size(image.Width, image.Height);
            bool flag = (double)val2 < (double)val1;
            return new Size(!flag ? frameSize.Width : Scale(image.Width, amount, frameSize.Width), flag ? frameSize.Height : this.Scale(image.Height, amount, frameSize.Height));
        }

        private int Scale(int value, float amount, int maxValue)
        {
            int num = this.Scale(value, amount);
            if (maxValue - num == 1)
                num = maxValue;
            return num;
        }

        private int Scale(int value, float amount)
        {
            return (int)Math.Round((double)value * (double)amount);
        }
    }
}
 
And here is the config to make this processor work - 
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:environment="http://www.sitecore.net/xmlconfig/environment/">
  <sitecore>    
    <pipelines>      
  <getMediaStream>
        <processor patch:instead="*[@type='Sitecore.Resources.Media.ResizeProcessor, Sitecore.Kernel']" type="<Your Namespace>.GifResizeProcessor, <Your DLL Name>" resolve="true"/>
      </getMediaStream>
    </pipelines>
  </sitecore>
</configuration>

Once you have the above code in place, if you resize the GIF, you will see the resized GIF with animation.




Thanks for reading this. Hope it helps you!!
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