如何使用 C# 调整动画 gif 图像的大小？

Question

Is there a method to create a copy of an animated gif image using C#?

What I want is to generate a copy of a given gif image using the height and width parameters that the user provides. I have tried for a couple of hours to accomplish this but the resulting image does not preserve the original animations.

Answer 1

Took me a while to find this, but finally found a solution:

Install Magick.NET via NuGet, license can be found here:
https://magick.codeplex.com/license

Example code:

var newWidth = 100;
using (var collection = new MagickImageCollection(new FileInfo(@"C:\test.gif")))
{
    collection.Coalesce();
    foreach (var image in collection)
    {
        image.Resize(newWidth, 0);
    }
    collection.Write(@"c:\resized.gif");
}

From my tests, this works with alpha channels and varying frame rates. Seems to be perfect!

Answer 2

You need to loop through the frames in the animated GIF and resize each one.

May also want to take a look at GifLib .

Answer 3

In case it helps someone in the future, I have found another solution that is much faster than Magick.NET (in processing the same gif, it takes only 3s instead of 50-60s than Magick.NET takes)

PhotoSauce.MagicScaler (Only work with Windows (.NET Core and .NET 5+) and partially works on Linux )

Example:

MagicImageProcessor.ProcessImage(@"\img\big.jpg", @"\img\small.jpg", new ProcessImageSettings { Width = 400 });

Resize with Bytes (Tested with png, jpg and gif):

public static byte[] ResizeImageBytes(byte[] imageBytes, int newWidth, int newHeight) {
    using (MemoryStream outStream = new()) {
        ProcessImageSettings processImageSettings = new() {
            Width = newWidth,
            Height = newHeight,
            ResizeMode = CropScaleMode.Stretch,
            HybridMode = HybridScaleMode.Turbo
        };
        MagicImageProcessor.ProcessImage(imageBytes, outStream, processImageSettings);
        return outStream.ToArray();
    }
}