Merge pull request #1212 from SixLabors/js/fix-1211

Swap buffers when encoding PNG with Filtered Adam7 Palette mode

src/ImageSharp/Formats/Png/PngEncoderCore.cs

@@ -1081,6 +1081,10 @@ namespace SixLabors.ImageSharp.Formats.Png
                         // encode data
                         IManagedByteBuffer r = this.EncodeAdam7IndexedPixelRow(destSpan);
                         deflateStream.Write(r.Array, 0, resultLength);
+
+                        IManagedByteBuffer temp = this.currentScanline;
+                        this.currentScanline = this.previousScanline;
+                        this.previousScanline = temp;
                     }
                 }
             }

tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs

@@ -199,12 +199,14 @@ namespace SixLabors.ImageSharp.Tests.Formats.Png
                 return;
             }
 
+            foreach (var filterMethod in PngFilterMethods)
+            {
                 foreach (PngInterlaceMode interlaceMode in InterlaceMode)
                 {
                     TestPngEncoderCore(
                     provider,
                     pngColorType,
-                PngFilterMethod.Adaptive,
+                    (PngFilterMethod)filterMethod[0],
                     pngBitDepth,
                     interlaceMode,
                     appendPngColorType: true,
@@ -212,6 +214,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Png
                     appendPngBitDepth: true);
                 }
             }
+        }
 
         [Theory]
         [WithTestPatternImages(24, 24, PixelTypes.Rgba32, PngColorType.Rgb, PngBitDepth.Bit8)]
@@ -231,13 +234,15 @@ namespace SixLabors.ImageSharp.Tests.Formats.Png
         [WithTestPatternImages(24, 24, PixelTypes.Rgba64, PngColorType.GrayscaleWithAlpha, PngBitDepth.Bit16)]
         public void WorksWithAllBitDepthsAndExcludeAllFilter<TPixel>(TestImageProvider<TPixel> provider, PngColorType pngColorType, PngBitDepth pngBitDepth)
           where TPixel : unmanaged, IPixel<TPixel>
+        {
+            foreach (var filterMethod in PngFilterMethods)
             {
                 foreach (PngInterlaceMode interlaceMode in InterlaceMode)
                 {
                     TestPngEncoderCore(
                     provider,
                     pngColorType,
-                PngFilterMethod.Adaptive,
+                    (PngFilterMethod)filterMethod[0],
                     pngBitDepth,
                     interlaceMode,
                     appendPngColorType: true,
@@ -246,6 +251,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Png
                     optimizeMethod: PngChunkFilter.ExcludeAll);
                 }
             }
+        }
 
         [Theory]
         [WithBlankImages(1, 1, PixelTypes.A8, PngColorType.GrayscaleWithAlpha, PngBitDepth.Bit8)]