Add test for legacy tga format

tests/ImageSharp.Tests/Formats/Tga/TgaDecoderTests.cs

@@ -733,6 +733,20 @@ namespace SixLabors.ImageSharp.Tests.Formats.Tga
             }
         }
 
+        // Test case for legacy format, when RLE crosses multiple lines:
+        // https://github.com/SixLabors/ImageSharp/pull/2172
+        [Theory]
+        [WithFile(Github_RLE_legacy, PixelTypes.Rgba32)]
+        public void TgaDecoder_CanDecode_LegacyFormat<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage(TgaDecoder))
+            {
+                image.DebugSave(provider);
+                ImageComparingUtils.CompareWithReferenceDecoder(provider, image);
+            }
+        }
+
         [Theory]
         [WithFile(Bit16BottomLeft, PixelTypes.Rgba32)]
         [WithFile(Bit24BottomLeft, PixelTypes.Rgba32)]

tests/ImageSharp.Tests/TestImages.cs

@@ -544,6 +544,8 @@ namespace SixLabors.ImageSharp.Tests
             public const string NoAlphaBits16BitRle = "Tga/16bit_rle_noalphabits.tga";
             public const string NoAlphaBits32Bit = "Tga/32bit_no_alphabits.tga";
             public const string NoAlphaBits32BitRle = "Tga/32bit_rle_no_alphabits.tga";
+
+            public const string Github_RLE_legacy = "Tga/Github_RLE_legacy.tga";
         }
 
         public static class Webp

tests/Images/Input/Tga/Github_RLE_legacy.tga

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:3570d2883a10a764577dd5174a9168320e8653b220800714da8e3880f752ab5e
+size 51253