Task 20918. Improving Png.Save and tests

Comments removing

update3

OpenRA.Game/FileFormats/Png.cs

@@ -16,6 +16,7 @@
 using System.Net;
 using System.Text;
 using ICSharpCode.SharpZipLib.Checksum;
+using ICSharpCode.SharpZipLib.Zip.Compression;
 using ICSharpCode.SharpZipLib.Zip.Compression.Streams;
 using OpenRA.Graphics;
 using OpenRA.Primitives;
@@ -371,13 +372,14 @@ public byte[] Save()
 
 				using (var data = new MemoryStream())
 				{
-					using (var compressed = new DeflaterOutputStream(data))
+					using (var compressed = new DeflaterOutputStream(data, new Deflater(Deflater.BEST_COMPRESSION)))
 					{
 						var rowStride = Width * PixelStride;
 						for (var y = 0; y < Height; y++)
 						{
-							// Write uncompressed scanlines for simplicity
-							compressed.WriteByte(0);
+							// Assuming no filtering for simplicity
+							const byte FilterType = 0;
+							compressed.WriteByte(FilterType);
 							compressed.Write(Data, y * rowStride, rowStride);
 						}
 

OpenRA.Test/OpenRA.Game/PngTest.cs

@@ -0,0 +1,162 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.IO;
+using System.Linq;
+using NUnit.Framework;
+using OpenRA.FileFormats;
+using OpenRA.Graphics;
+using OpenRA.Primitives;
+
+namespace OpenRA.Test
+{
+	[TestFixture]
+	public class PngTests
+	{
+		[Test]
+		public void Save_ShouldProduceValidPngFile()
+		{
+			// Arrange
+			var colors = Enumerable.Range(0, 256).Select(i => Color.FromArgb(i, i, i)).ToArray();
+			var png = new Png(new byte[10 * 20], SpriteFrameType.Indexed8, 10, 20, colors);
+
+			// Act
+			var result = png.Save();
+
+			// Assert
+			Assert.IsTrue(Png.Verify(new MemoryStream(result)));
+		}
+
+		[Test]
+		public void Save_Method_Should_Write_Indexed8_Palette_If_256_Colors_Or_Less()
+		{
+			// Arrange
+			var colors = Enumerable.Range(0, 256).Select(i => Color.FromArgb(i, i, i)).ToArray();
+			var png = new Png(new byte[10 * 20], SpriteFrameType.Indexed8, 10, 20, colors);
+
+			// Act
+			var result = png.Save();
+
+			// Assert
+			// Byte at index 25 contains color type information
+			// 0x03 represents Indexed8 with a palette
+			var colorTypeByte = result[25];
+			Assert.That(colorTypeByte, Is.EqualTo(0x03));
+		}
+
+		[Test]
+		public void Save_Method_Should_Write_Rgba32_If_Alpha_Channel_Required()
+		{
+			// Arrange
+			var png = new Png(new byte[10 * 20 * 4], SpriteFrameType.Rgba32, 10, 20);
+
+			// Act
+			var result = png.Save();
+
+			// Assert
+			// Byte at index 25 contains color type information
+			// 0x06 represents RGBA32 with alpha
+			var colorTypeByte = result[25];
+			Assert.That(colorTypeByte, Is.EqualTo(0x06));
+		}
+
+		[Test]
+		public void Save_ShouldThrowException_WhenDataLenghtNotEqualExpectedLenght()
+		{
+			// Arrange
+			var colors = Enumerable.Range(0, 256).Select(i => Color.FromArgb(i, i, i)).ToArray();
+
+			// Act
+			void TestDelegate() => new Png(new byte[10 * 20], SpriteFrameType.Indexed8, 100, 20, colors);
+
+			// Assert
+			var ex = Assert.Throws<InvalidDataException>(TestDelegate);
+			Assert.That(ex.Message, Is.EqualTo("Input data does not match expected length"));
+		}
+
+		[Test]
+		public void PngConstructor_InvalidSignature_ThrowsInvalidDataException()
+		{
+			// Arrange
+			byte[] invalidSignature = { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 };
+
+			// Act & Assert
+			var exception = Assert.Throws<InvalidDataException>(() => new Png(new MemoryStream(invalidSignature)));
+			StringAssert.Contains("PNG Signature is bogus", exception.Message);
+		}
+
+		[Test]
+		public void PngConstructor_HeaderNotFirst_ThrowsInvalidDataException()
+		{
+			// Arrange
+			var invalidPngData = new byte[]
+			{
+				0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
+				0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4e, 0x44,
+				0x00, 0x00, 0x00, 0x00,
+			};
+
+			// Act & Assert
+			var exception = Assert.Throws<InvalidDataException>(() => new Png(new MemoryStream(invalidPngData)));
+			StringAssert.Contains("Invalid PNG file - header does not appear first.", exception.Message);
+		}
+
+		[Test]
+		public void PngConstructor_DuplicateIhdrHeader_ThrowsInvalidDataException()
+		{
+			// Arrange
+			var invalidPngData = new byte[]
+			{
+				0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
+				0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52,
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				0x49, 0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x00,
+			};
+
+			using (var stream = new MemoryStream(invalidPngData))
+			{
+				// Act & Assert
+				var exception = Assert.Throws<EndOfStreamException>(() => new Png(stream));
+			}
+		}
+
+		public void PngConstructor_CompressionMethodNotSupported_ThrowsInvalidDataException()
+		{
+			// Arrange
+			var invalidPngData = new byte[]
+			{
+				0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
+				0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52,
+				0x00, 0x00, 0x00, 0x00, 0x08, 0x02, 0x00, 0x00,
+				0x49, 0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x00,
+			};
+
+			using (var stream = new MemoryStream(invalidPngData))
+			{
+				// Act & Assert
+				var exception = Assert.Throws<InvalidDataException>(() => new Png(stream));
+				Assert.AreEqual("Compression method not supported", exception.Message);
+			}
+		}
+
+		[Test]
+		public void Constructor_ThrowsExceptionForNullPaletteIfTypeIsIndexed8()
+		{
+			// Arrange
+			const int Width = 100;
+			const int Height = 100;
+			const SpriteFrameType Type = SpriteFrameType.Indexed8;
+
+			// Act and Assert
+			Assert.Throws<InvalidDataException>(() => new Png(new byte[Width * Height], Type, Width, Height, null));
+		}
+	}
+}