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bma  
#1 Posted : Monday, January 25, 2016 3:01:53 AM(UTC)
bma

Rank: Member

Groups: Member
Joined: 1/12/2016(UTC)
Posts: 23

Thanks: 8 times
Hello,

When I try to resize an animated gif image, the new image loses quality and is deformed (See images attached).


Code:
public byte[] ResizeGif(byte[] media, int width, int height)
{
	using (var imageStream = new MemoryStream(media))
	using (var exportedImageStream = new MemoryStream())
	using (var imageReader = ImageReader.Create(imageStream))
	{

		using (var imageWriter = new GifWriter(exportedImageStream))
		{
			imageWriter.BackgroundIndex = ((GifReader)imageReader).BackgroundEntryIndex;
			imageWriter.Palette = ((GifReader)imageReader).Palette;
			imageWriter.PlaybackCount = ((GifReader)imageReader).PlaybackCount;

			for (var i = 0; i < ((GifReader)imageReader).Frames.Count; i++)
			{
				// Read a frame
				using (var frame = ((GifReader)imageReader).Frames[i])
				using (var bitmap = frame.GetBitmap())
				{
					Console.WriteLine(i);
					// Preserve the original palette
					var palette = bitmap.Palette;
					// Preserve the original pixel format
					var pixelFormat = bitmap.PixelFormat;

					// Convert the bitmap to a non-indexed format
					bitmap.ColorManagement.Convert(ColorSpace.Rgb, true, false);

					// Resize the bitmap in a high quality mode
					bitmap.Transforms.Resize(width, height, ResizeInterpolationMode.High);

					// Return to the indexed format
					bitmap.Palette = palette;
					bitmap.ColorManagement.Convert(pixelFormat);

					// Copy frame delay
					imageWriter.FrameOptions.Delay = frame.Delay;

					// Add the frame
					Pipeline.Run(bitmap + imageWriter);
				}
			}
		}

		return exportedImageStream.GetBuffer();
	}
}


Kind regards

Edited by user Monday, January 25, 2016 3:05:38 AM(UTC)  | Reason: Not specified

File Attachment(s):
image_resized.gif (8,192kb) downloaded 4 time(s).
original_image.gif (5,332kb) downloaded 2 time(s).
Fedor  
#2 Posted : Tuesday, January 26, 2016 5:58:23 AM(UTC)
Fedor

Rank: Advanced Member

Groups: Member, Administration, Moderator
Joined: 7/28/2003(UTC)
Posts: 1,558

Thanks: 5 times
Was thanked: 62 time(s) in 61 post(s)
Here is the updated code which fixes the problems:

Code:
public byte[] ResizeGif(byte[] media, int width, int height)
{
	using (var imageStream = new MemoryStream(media))
	using (var exportedImageStream = new MemoryStream())
	using (var imageReader = ImageReader.Create(imageStream))
	{
		var kX = (float)width / (float)imageReader.Width;
		var kY = (float)height / (float)imageReader.Height;

		using (var imageWriter = new GifWriter(exportedImageStream))
		{
			imageWriter.BackgroundIndex = ((GifReader)imageReader).BackgroundEntryIndex;
			imageWriter.Palette = ((GifReader)imageReader).Palette;
			imageWriter.PlaybackCount = ((GifReader)imageReader).PlaybackCount;

			for (var i = 0; i < ((GifReader)imageReader).Frames.Count; i++)
			{
				// Read a frame
				using (var frame = ((GifReader)imageReader).Frames[i])
				using (var bitmap = frame.GetBitmap())
				{
					Console.WriteLine(i);
					bitmap.Save("../../../" + i + ".png");

					// Preserve the original palette
					var palette = bitmap.Palette;
					// Preserve the original pixel format
					var pixelFormat = bitmap.PixelFormat;

					// Convert the bitmap to a non-indexed format
					bitmap.ColorManagement.Convert(ColorSpace.Rgb, true, false);

					var newWidth = Math.Max(1, (int)((float)bitmap.Width * kX));
					var newHeight = Math.Max(1, (int)((float)bitmap.Height * kY));
					//Use low quality resize mode to prevent noise
					bitmap.Transforms.Resize(newWidth, newHeight, ResizeInterpolationMode.Low);

					// Return to the indexed format
					bitmap.ColorManagement.Palette = palette;
					bitmap.ColorManagement.Convert(pixelFormat);

					// Copy frame delay
					imageWriter.FrameOptions.Left = (ushort)((float)frame.Left * kX);
					imageWriter.FrameOptions.Top = (ushort)((float)frame.Top * kY);
					imageWriter.FrameOptions.Delay = frame.Delay;
					imageWriter.FrameOptions.DisposalMethod = frame.DisposalMethod;

					// Add the frame
					Pipeline.Run(bitmap + imageWriter);
				}
			}
		}

		return exportedImageStream.GetBuffer();
	}
}

Edited by user Tuesday, January 26, 2016 8:34:32 AM(UTC)  | Reason: Not specified

Best regards,
Fedor Skvortsov
thanks 1 user thanked Fedor for this useful post.
bma on 1/26/2016(UTC)
bma  
#3 Posted : Tuesday, January 26, 2016 6:21:18 AM(UTC)
bma

Rank: Member

Groups: Member
Joined: 1/12/2016(UTC)
Posts: 23

Thanks: 8 times
Thank you! It worked!
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