Drop netcoreapp3.1 and net5.0

Also replace System.Drawing with SkiaSharp

Dithery-cli.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFrameworks>netcoreapp3.1;net5.0;net6.0;net7.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net6.0;net7.0;net8.0</TargetFrameworks>
     <RootNamespace>Dithery_cli</RootNamespace>
 
     <PackAsTool>true</PackAsTool>
@@ -19,7 +19,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="System.Drawing.Common" Version="5.0.2" />
+    <PackageReference Include="SkiaSharp" Version="2.88.6" />
     <PackageReference Include="LibDithering" Version="1.0.1" />
   </ItemGroup>
 

FileWriting.cs

@@ -1,28 +1,29 @@
 using System;
 using System.IO;
-using System.Drawing;
+using SkiaSharp;
 
 namespace Dithery_cli
 {
 	public static class FileWriting
 	{
-		public static void DitherAndWritePngFile(string outputFilename, Bitmap bitmap, DitheringBase<byte> ditherer, bool writeToSameBitmap = true)
+		public static void DitherAndWritePngFile(string outputFilename, SKBitmap bitmap, DitheringBase<byte> ditherer, bool writeToSameBitmap = true)
 		{
 			byte[] bytes = ReadWriteBitmaps.ReadBitmapToColorBytes(bitmap);
 
 			TempByteImageFormat temp = new TempByteImageFormat(bytes, bitmap.Width, bitmap.Height, 3);
 			temp = (TempByteImageFormat)ditherer.DoDithering(temp);
 
+			using FileStream fs = new(outputFilename, FileMode.Create);
 			if (writeToSameBitmap)
 			{
 				ReadWriteBitmaps.WriteToBitmap(bitmap, temp.GetPixelChannels);
-				bitmap.Save(outputFilename, System.Drawing.Imaging.ImageFormat.Png);
+				bitmap.Encode(fs, SKEncodedImageFormat.Png, quality: 100);
 			}
 			else
 			{
-				Bitmap tempBitmap = new Bitmap(bitmap.Width, bitmap.Height, bitmap.PixelFormat);
+				SKBitmap tempBitmap = new SKBitmap(bitmap.Width, bitmap.Height, bitmap.ColorType, bitmap.AlphaType);
 				ReadWriteBitmaps.WriteToBitmap(tempBitmap, temp.GetPixelChannels);
-				tempBitmap.Save(outputFilename, System.Drawing.Imaging.ImageFormat.Png);
+				tempBitmap.Encode(fs, SKEncodedImageFormat.Png, quality: 100);
 			}
 		}
 	}

Program.cs

@@ -1,7 +1,8 @@
 using System;
 using System.IO;
 using System.Collections.Generic;
-using System.Drawing;
+using SkiaSharp;
+
 using System.Linq;
 
 namespace Dithery_cli
@@ -163,7 +164,7 @@ static void Main(string[] args)
 				valuesAsList.Remove(DitheringMethod.None);
 
 				using(FileStream bitmapStream = new FileStream(inputFile, FileMode.Open, FileAccess.Read))
-				using(var image = new Bitmap(bitmapStream))
+				using(var image = SKBitmap.Decode(bitmapStream))
 				{
 					if (outputFormat == OutputFormat.SingleImage)
 					{
@@ -184,7 +185,7 @@ static void Main(string[] args)
 						List<(MemoryStream pngData, string text)> images = new List<(MemoryStream pngData, string text)>();
 
 						MemoryStream originalImageMemoryStream = new MemoryStream();
-						image.Save(originalImageMemoryStream, System.Drawing.Imaging.ImageFormat.Png);
+						image.Encode(originalImageMemoryStream, SKEncodedImageFormat.Png, quality: 100);
 						images.Add((originalImageMemoryStream, "Original"));
 
 						foreach (DitheringMethod ditheringMethod in valuesAsList)
@@ -203,7 +204,7 @@ static void Main(string[] args)
 			{
 				DitheringBase<byte> ditherer = GetDitherer(dithering, colorReductionMethod);
 				using(FileStream bitmapStream = new FileStream(inputFile, FileMode.Open, FileAccess.Read))
-				using(var image = new Bitmap(bitmapStream))
+				using(var image = SKBitmap.Decode(bitmapStream))
 				{
 					if (outputFormat == OutputFormat.SingleImage)
 					{
@@ -212,7 +213,7 @@ static void Main(string[] args)
 					else if (outputFormat == OutputFormat.HTMLBasic)
 					{
 						MemoryStream originalImageMemoryStream = new MemoryStream();
-						image.Save(originalImageMemoryStream, System.Drawing.Imaging.ImageFormat.Png);
+						image.Encode(originalImageMemoryStream, SKEncodedImageFormat.Png, quality: 100);
 
 						MemoryStream ditheredImageMemoryStream = new MemoryStream();
 						StreamWriting.DitherAndWritePngStream(ditheredImageMemoryStream, image, ditherer);

ReadWriteBitmaps.cs

@@ -1,25 +1,25 @@
 using System;
 using System.IO;
-using System.Drawing;
+using SkiaSharp;
 
 namespace Dithery_cli
 {
 	public static class ReadWriteBitmaps
 	{
-		public static void WriteToBitmap(Bitmap bitmap, Func<int, int, byte[]> reader)
+		public static void WriteToBitmap(SKBitmap bitmap, Func<int, int, byte[]> reader)
 		{
 			for (int y = 0; y < bitmap.Height; y++)
 			{
 				for (int x = 0; x < bitmap.Width; x++)
 				{
 					byte[] read = reader(x, y);
-					Color color = Color.FromArgb((byte)read[0], (byte)read[1], (byte)read[2]);
+					SKColor color = new SKColor((byte)read[0], (byte)read[1], (byte)read[2]);
 					bitmap.SetPixel(x, y, color);
 				}
 			}
 		}
 
-		public static byte[] ReadBitmapToColorBytes(Bitmap bitmap)
+		public static byte[] ReadBitmapToColorBytes(SKBitmap bitmap)
 		{
 			int width = bitmap.Width;
 			int height = bitmap.Height;
@@ -30,11 +30,11 @@ public static byte[] ReadBitmapToColorBytes(Bitmap bitmap)
 			{
 				for (int x = 0; x < bitmap.Width; x++)
 				{
-					Color color = bitmap.GetPixel(x, y);
+					SKColor color = bitmap.GetPixel(x, y);
 					int arrayIndex = y * width * channelsPerPixel + x * channelsPerPixel;
-					returnValue[arrayIndex + 0] = color.R;
-					returnValue[arrayIndex + 1] = color.G;
-					returnValue[arrayIndex + 2] = color.B;
+					returnValue[arrayIndex + 0] = color.Red;
+					returnValue[arrayIndex + 1] = color.Green;
+					returnValue[arrayIndex + 2] = color.Blue;
 				}
 			}
 

StreamWriting.cs

@@ -1,11 +1,11 @@
 using System.IO;
-using System.Drawing;
+using SkiaSharp;
 
 namespace Dithery_cli
 {
 	public static class StreamWriting
 	{
-		public static void DitherAndWritePngStream(Stream outputStream, Bitmap bitmap, DitheringBase<byte> ditherer, bool writeToSameBitmap = true)
+		public static void DitherAndWritePngStream(Stream outputStream, SKBitmap bitmap, DitheringBase<byte> ditherer, bool writeToSameBitmap = true)
 		{
 			byte[] bytes = ReadWriteBitmaps.ReadBitmapToColorBytes(bitmap);
 
@@ -15,13 +15,13 @@ public static void DitherAndWritePngStream(Stream outputStream, Bitmap bitmap, D
 			if (writeToSameBitmap)
 			{
 				ReadWriteBitmaps.WriteToBitmap(bitmap, temp.GetPixelChannels);
-				bitmap.Save(outputStream, System.Drawing.Imaging.ImageFormat.Png);
+				bitmap.Encode(outputStream, SKEncodedImageFormat.Png, quality: 100);
 			}
 			else
 			{
-				Bitmap tempBitmap = new Bitmap(bitmap.Width, bitmap.Height, bitmap.PixelFormat);
+				SKBitmap tempBitmap = new SKBitmap(bitmap.Width, bitmap.Height, bitmap.ColorType, bitmap.AlphaType);
 				ReadWriteBitmaps.WriteToBitmap(tempBitmap, temp.GetPixelChannels);
-				tempBitmap.Save(outputStream, System.Drawing.Imaging.ImageFormat.Png);
+				tempBitmap.Encode(outputStream, SKEncodedImageFormat.Png, quality: 100);
 			}
 		}
 	}