UnrealEngineUWP/Engine/Source/Programs/AutomationTool/AutomationUtils/ImageUtils.cs

// Copyright 1998-2019 Epic Games, Inc. All Rights Reserved.

using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.Linq;

namespace AutomationTool
{
	public static class ImageUtils
	{
		/// <summary>
		/// Resave an image file as a .jpg file, with the specified quality and scale.
		/// </summary>
		public static void ResaveImageAsJpgWithScaleAndQuality(string SrcImagePath, string DstImagePath, float Scale, int JpgQuality)
		{
			// Find the built-in jpg encoder
			var Codec = ImageCodecInfo.GetImageDecoders().Where(d => d.FormatID == ImageFormat.Jpeg.Guid).First();

			using (var SrcImage = Image.FromFile(SrcImagePath))
			{
				// Create a resized destination bitmap
				var DstRect = new Rectangle(0, 0, (int)(SrcImage.Width * Scale), (int)(SrcImage.Height * Scale));
				using (var DstImage = new Bitmap(DstRect.Width, DstRect.Height))
				{
					DstImage.SetResolution(SrcImage.HorizontalResolution, SrcImage.VerticalResolution);

					// Draw and scale the original image into the new bitmap.
					using (var Grfx = Graphics.FromImage(DstImage))
					using (var ImageAttrs = new ImageAttributes())
					{
						Grfx.InterpolationMode = InterpolationMode.HighQualityBicubic;
						Grfx.CompositingQuality = CompositingQuality.HighQuality;
						Grfx.CompositingMode = CompositingMode.SourceCopy;
						Grfx.PixelOffsetMode = PixelOffsetMode.HighQuality;
						Grfx.SmoothingMode = SmoothingMode.HighQuality;

						ImageAttrs.SetWrapMode(WrapMode.TileFlipXY);
						Grfx.DrawImage(SrcImage, DstRect, 0, 0, SrcImage.Width, SrcImage.Height, GraphicsUnit.Pixel, ImageAttrs);
					}
					
					// Save using the Jpg encoder and a custom quality level.
					var EncParams = new EncoderParameters(1);
					EncParams.Param[0] = new EncoderParameter(Encoder.Quality, JpgQuality);
					DstImage.Save(DstImagePath, Codec, EncParams);
				}
			}
		}
	}
}