diff --git a/src/ImageSharp/Formats/Png/PngDecoderCore.cs b/src/ImageSharp/Formats/Png/PngDecoderCore.cs index a96c53c10..c4b10b4dc 100644 --- a/src/ImageSharp/Formats/Png/PngDecoderCore.cs +++ b/src/ImageSharp/Formats/Png/PngDecoderCore.cs @@ -228,8 +228,7 @@ internal sealed class PngDecoderCore : IImageDecoderInternals PngThrowHelper.ThrowMissingFrameControl(); } - previousFrameControl ??= new((uint)this.header.Width, (uint)this.header.Height); - this.InitializeFrame(previousFrameControl.Value, currentFrameControl.Value, image, previousFrame, out currentFrame); + this.InitializeFrame(previousFrameControl, currentFrameControl.Value, image, previousFrame, out currentFrame); this.currentStream.Position += 4; this.ReadScanlines( @@ -240,11 +239,16 @@ internal sealed class PngDecoderCore : IImageDecoderInternals currentFrameControl.Value, cancellationToken); - previousFrame = currentFrame; - previousFrameControl = currentFrameControl; + // if current frame dispose is restore to previous, then from future frame's perspective, it never happened + if (currentFrameControl.Value.DisposeOperation != PngDisposalMethod.RestoreToPrevious) + { + previousFrame = currentFrame; + previousFrameControl = currentFrameControl; + } + break; case PngChunkType.Data: - + pngMetadata.AnimateRootFrame = currentFrameControl != null; currentFrameControl ??= new((uint)this.header.Width, (uint)this.header.Height); if (image is null) { @@ -261,9 +265,12 @@ internal sealed class PngDecoderCore : IImageDecoderInternals this.ReadNextDataChunk, currentFrameControl.Value, cancellationToken); + if (pngMetadata.AnimateRootFrame) + { + previousFrame = currentFrame; + previousFrameControl = currentFrameControl; + } - previousFrame = currentFrame; - previousFrameControl = currentFrameControl; break; case PngChunkType.Palette: this.palette = chunk.Data.GetSpan().ToArray(); @@ -632,7 +639,7 @@ internal sealed class PngDecoderCore : IImageDecoderInternals /// The previous frame. /// The created frame private void InitializeFrame( - FrameControl previousFrameControl, + FrameControl? previousFrameControl, FrameControl currentFrameControl, Image image, ImageFrame? previousFrame, @@ -645,12 +652,16 @@ internal sealed class PngDecoderCore : IImageDecoderInternals frame = image.Frames.AddFrame(previousFrame ?? image.Frames.RootFrame); // If the first `fcTL` chunk uses a `dispose_op` of APNG_DISPOSE_OP_PREVIOUS it should be treated as APNG_DISPOSE_OP_BACKGROUND. - if (previousFrameControl.DisposeOperation == PngDisposalMethod.RestoreToBackground - || (previousFrame is null && previousFrameControl.DisposeOperation == PngDisposalMethod.RestoreToPrevious)) + // So, if restoring to before first frame, clear entire area. Same if first frame (previousFrameControl null). + if (previousFrameControl == null || (previousFrame is null && previousFrameControl.Value.DisposeOperation == PngDisposalMethod.RestoreToPrevious)) + { + Buffer2DRegion pixelRegion = frame.PixelBuffer.GetRegion(); + pixelRegion.Clear(); + } + else if (previousFrameControl.Value.DisposeOperation == PngDisposalMethod.RestoreToBackground) { - Rectangle restoreArea = previousFrameControl.Bounds; - Rectangle interest = Rectangle.Intersect(frame.Bounds(), restoreArea); - Buffer2DRegion pixelRegion = frame.PixelBuffer.GetRegion(interest); + Rectangle restoreArea = previousFrameControl.Value.Bounds; + Buffer2DRegion pixelRegion = frame.PixelBuffer.GetRegion(restoreArea); pixelRegion.Clear(); } diff --git a/src/ImageSharp/Formats/Png/PngEncoderCore.cs b/src/ImageSharp/Formats/Png/PngEncoderCore.cs index ea94270f2..802e4dd6a 100644 --- a/src/ImageSharp/Formats/Png/PngEncoderCore.cs +++ b/src/ImageSharp/Formats/Png/PngEncoderCore.cs @@ -161,6 +161,7 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable ImageFrame? clonedFrame = null; ImageFrame currentFrame = image.Frames.RootFrame; + int currentFrameIndex = 0; bool clearTransparency = this.encoder.TransparentColorMode is PngTransparentColorMode.Clear; if (clearTransparency) @@ -189,29 +190,50 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable if (image.Frames.Count > 1) { - this.WriteAnimationControlChunk(stream, (uint)image.Frames.Count, pngMetadata.RepeatCount); + this.WriteAnimationControlChunk(stream, (uint)(image.Frames.Count - (pngMetadata.AnimateRootFrame ? 0 : 1)), pngMetadata.RepeatCount); + } + + // If the first frame isn't animated, write it as usual and skip it when writing animated frames + if (!pngMetadata.AnimateRootFrame || image.Frames.Count == 1) + { + FrameControl frameControl = new((uint)this.width, (uint)this.height); + this.WriteDataChunks(frameControl, currentFrame.PixelBuffer.GetRegion(), quantized, stream, false); + currentFrameIndex++; + } - // Write the first frame. + if (image.Frames.Count > 1) + { + // Write the first animated frame. + currentFrame = image.Frames[currentFrameIndex]; PngFrameMetadata frameMetadata = GetPngFrameMetadata(currentFrame); PngDisposalMethod previousDisposal = frameMetadata.DisposalMethod; FrameControl frameControl = this.WriteFrameControlChunk(stream, frameMetadata, currentFrame.Bounds(), 0); - this.WriteDataChunks(frameControl, currentFrame.PixelBuffer.GetRegion(), quantized, stream, false); + uint sequenceNumber = 1; + if (pngMetadata.AnimateRootFrame) + { + this.WriteDataChunks(frameControl, currentFrame.PixelBuffer.GetRegion(), quantized, stream, false); + } + else + { + sequenceNumber += this.WriteDataChunks(frameControl, currentFrame.PixelBuffer.GetRegion(), quantized, stream, true); + } + + currentFrameIndex++; // Capture the global palette for reuse on subsequent frames. ReadOnlyMemory? previousPalette = quantized?.Palette.ToArray(); // Write following frames. - uint increment = 0; ImageFrame previousFrame = image.Frames.RootFrame; // This frame is reused to store de-duplicated pixel buffers. using ImageFrame encodingFrame = new(image.Configuration, previousFrame.Size()); - for (int i = 1; i < image.Frames.Count; i++) + for (; currentFrameIndex < image.Frames.Count; currentFrameIndex++) { ImageFrame? prev = previousDisposal == PngDisposalMethod.RestoreToBackground ? null : previousFrame; - currentFrame = image.Frames[i]; - ImageFrame? nextFrame = i < image.Frames.Count - 1 ? image.Frames[i + 1] : null; + currentFrame = image.Frames[currentFrameIndex]; + ImageFrame? nextFrame = currentFrameIndex < image.Frames.Count - 1 ? image.Frames[currentFrameIndex + 1] : null; frameMetadata = GetPngFrameMetadata(currentFrame); bool blend = frameMetadata.BlendMethod == PngBlendMethod.Over; @@ -232,22 +254,17 @@ internal sealed class PngEncoderCore : IImageEncoderInternals, IDisposable } // Each frame control sequence number must be incremented by the number of frame data chunks that follow. - frameControl = this.WriteFrameControlChunk(stream, frameMetadata, bounds, (uint)i + increment); + frameControl = this.WriteFrameControlChunk(stream, frameMetadata, bounds, sequenceNumber); // Dispose of previous quantized frame and reassign. quantized?.Dispose(); quantized = this.CreateQuantizedImageAndUpdateBitDepth(pngMetadata, encodingFrame, bounds, previousPalette); - increment += this.WriteDataChunks(frameControl, encodingFrame.PixelBuffer.GetRegion(bounds), quantized, stream, true); + sequenceNumber += this.WriteDataChunks(frameControl, encodingFrame.PixelBuffer.GetRegion(bounds), quantized, stream, true) + 1; previousFrame = currentFrame; previousDisposal = frameMetadata.DisposalMethod; } } - else - { - FrameControl frameControl = new((uint)this.width, (uint)this.height); - this.WriteDataChunks(frameControl, currentFrame.PixelBuffer.GetRegion(), quantized, stream, false); - } this.WriteEndChunk(stream); diff --git a/src/ImageSharp/Formats/Png/PngMetadata.cs b/src/ImageSharp/Formats/Png/PngMetadata.cs index 93ddcf263..d9028dd80 100644 --- a/src/ImageSharp/Formats/Png/PngMetadata.cs +++ b/src/ImageSharp/Formats/Png/PngMetadata.cs @@ -29,6 +29,7 @@ public class PngMetadata : IDeepCloneable this.InterlaceMethod = other.InterlaceMethod; this.TransparentColor = other.TransparentColor; this.RepeatCount = other.RepeatCount; + this.AnimateRootFrame = other.AnimateRootFrame; if (other.ColorTable?.Length > 0) { @@ -83,6 +84,11 @@ public class PngMetadata : IDeepCloneable /// public uint RepeatCount { get; set; } = 1; + /// + /// Gets or sets a value indicating whether the root frame is shown as part of the animated sequence + /// + public bool AnimateRootFrame { get; set; } = true; + /// public IDeepCloneable DeepClone() => new PngMetadata(this); diff --git a/src/ImageSharp/Formats/Png/PngScanlineProcessor.cs b/src/ImageSharp/Formats/Png/PngScanlineProcessor.cs index f217515e3..b327ed21b 100644 --- a/src/ImageSharp/Formats/Png/PngScanlineProcessor.cs +++ b/src/ImageSharp/Formats/Png/PngScanlineProcessor.cs @@ -198,8 +198,9 @@ internal static class PngScanlineProcessor ref byte scanlineSpanRef = ref MemoryMarshal.GetReference(scanlineSpan); ref TPixel rowSpanRef = ref MemoryMarshal.GetReference(rowSpan); ref Color paletteBase = ref MemoryMarshal.GetReference(palette.Value.Span); + uint offset = pixelOffset + frameControl.XOffset; - for (nuint x = pixelOffset, o = 0; x < frameControl.XMax; x += increment, o++) + for (nuint x = offset, o = 0; x < frameControl.XMax; x += increment, o++) { uint index = Unsafe.Add(ref scanlineSpanRef, o); pixel.FromRgba32(Unsafe.Add(ref paletteBase, index).ToRgba32()); diff --git a/tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs b/tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs index 9b165526e..9ff368d4e 100644 --- a/tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs +++ b/tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs @@ -87,7 +87,9 @@ public partial class PngDecoderTests TestImages.Png.DisposeBackgroundRegion, TestImages.Png.DisposePreviousFirst, TestImages.Png.DisposeBackgroundBeforeRegion, - TestImages.Png.BlendOverMultiple + TestImages.Png.BlendOverMultiple, + TestImages.Png.FrameOffset, + TestImages.Png.DefaultNotAnimated }; [Theory] diff --git a/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.Chunks.cs b/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.Chunks.cs index 044da2193..76fd260dd 100644 --- a/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.Chunks.cs +++ b/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.Chunks.cs @@ -3,6 +3,7 @@ using System.Buffers.Binary; using SixLabors.ImageSharp.Formats.Png; +using SixLabors.ImageSharp.Formats.Png.Chunks; using SixLabors.ImageSharp.PixelFormats; // ReSharper disable InconsistentNaming @@ -59,6 +60,38 @@ public partial class PngEncoderTests } } + [Theory] + [WithFile(TestImages.Png.DefaultNotAnimated, PixelTypes.Rgba32)] + [WithFile(TestImages.Png.APng, PixelTypes.Rgba32)] + public void AcTL_CorrectlyWritten(TestImageProvider provider) + where TPixel : unmanaged, IPixel + { + using Image image = provider.GetImage(PngDecoder.Instance); + PngMetadata metadata = image.Metadata.GetPngMetadata(); + int correctFrameCount = image.Frames.Count - (metadata.AnimateRootFrame ? 0 : 1); + using MemoryStream memStream = new(); + image.Save(memStream, PngEncoder); + memStream.Position = 0; + Span bytesSpan = memStream.ToArray().AsSpan(8); // Skip header. + bool foundAcTl = false; + while (bytesSpan.Length > 0 && !foundAcTl) + { + int length = BinaryPrimitives.ReadInt32BigEndian(bytesSpan[..4]); + PngChunkType type = (PngChunkType)BinaryPrimitives.ReadInt32BigEndian(bytesSpan.Slice(4, 4)); + if (type == PngChunkType.AnimationControl) + { + AnimationControl control = AnimationControl.Parse(bytesSpan[8..]); + foundAcTl = true; + Assert.True(control.NumberFrames == correctFrameCount); + Assert.True(control.NumberPlays == metadata.RepeatCount); + } + + bytesSpan = bytesSpan[(4 + 4 + length + 4)..]; + } + + Assert.True(foundAcTl); + } + [Theory] [InlineData(PngChunkType.Gamma)] [InlineData(PngChunkType.Chroma)] diff --git a/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs b/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs index 950f1d2e3..ca5aae961 100644 --- a/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs +++ b/tests/ImageSharp.Tests/Formats/Png/PngEncoderTests.cs @@ -447,6 +447,8 @@ public partial class PngEncoderTests [Theory] [WithFile(TestImages.Png.APng, PixelTypes.Rgba32)] + [WithFile(TestImages.Png.DefaultNotAnimated, PixelTypes.Rgba32)] + [WithFile(TestImages.Png.FrameOffset, PixelTypes.Rgba32)] public void Encode_APng(TestImageProvider provider) where TPixel : unmanaged, IPixel { @@ -458,15 +460,17 @@ public partial class PngEncoderTests image.DebugSave(provider: provider, encoder: PngEncoder, null, false); using Image output = Image.Load(memStream); - ImageComparer.Exact.VerifySimilarity(output, image); - Assert.Equal(5, image.Frames.Count); + // some loss from original, due to compositing + ImageComparer.TolerantPercentage(0.01f).VerifySimilarity(output, image); + Assert.Equal(image.Frames.Count, output.Frames.Count); PngMetadata originalMetadata = image.Metadata.GetPngMetadata(); PngMetadata outputMetadata = output.Metadata.GetPngMetadata(); Assert.Equal(originalMetadata.RepeatCount, outputMetadata.RepeatCount); + Assert.Equal(originalMetadata.AnimateRootFrame, outputMetadata.AnimateRootFrame); for (int i = 0; i < image.Frames.Count; i++) { diff --git a/tests/ImageSharp.Tests/Formats/Png/PngMetadataTests.cs b/tests/ImageSharp.Tests/Formats/Png/PngMetadataTests.cs index b3c122a7a..225e4deef 100644 --- a/tests/ImageSharp.Tests/Formats/Png/PngMetadataTests.cs +++ b/tests/ImageSharp.Tests/Formats/Png/PngMetadataTests.cs @@ -32,7 +32,8 @@ public class PngMetadataTests InterlaceMethod = PngInterlaceMode.Adam7, Gamma = 2, TextData = new List { new PngTextData("name", "value", "foo", "bar") }, - RepeatCount = 123 + RepeatCount = 123, + AnimateRootFrame = false }; PngMetadata clone = (PngMetadata)meta.DeepClone(); @@ -44,6 +45,7 @@ public class PngMetadataTests Assert.False(meta.TextData.Equals(clone.TextData)); Assert.True(meta.TextData.SequenceEqual(clone.TextData)); Assert.True(meta.RepeatCount == clone.RepeatCount); + Assert.True(meta.AnimateRootFrame == clone.AnimateRootFrame); clone.BitDepth = PngBitDepth.Bit2; clone.ColorType = PngColorType.Palette; @@ -144,6 +146,26 @@ public class PngMetadataTests VerifyExifDataIsPresent(exif); } + [Theory] + [WithFile(TestImages.Png.DefaultNotAnimated, PixelTypes.Rgba32)] + public void Decode_IdentifiesDefaultFrameNotAnimated(TestImageProvider provider) + where TPixel : unmanaged, IPixel + { + using Image image = provider.GetImage(PngDecoder.Instance); + PngMetadata meta = image.Metadata.GetFormatMetadata(PngFormat.Instance); + Assert.False(meta.AnimateRootFrame); + } + + [Theory] + [WithFile(TestImages.Png.APng, PixelTypes.Rgba32)] + public void Decode_IdentifiesDefaultFrameAnimated(TestImageProvider provider) + where TPixel : unmanaged, IPixel + { + using Image image = provider.GetImage(PngDecoder.Instance); + PngMetadata meta = image.Metadata.GetFormatMetadata(PngFormat.Instance); + Assert.True(meta.AnimateRootFrame); + } + [Theory] [WithFile(TestImages.Png.PngWithMetadata, PixelTypes.Rgba32)] public void Decode_IgnoresExifData_WhenIgnoreMetadataIsTrue(TestImageProvider provider) diff --git a/tests/ImageSharp.Tests/TestImages.cs b/tests/ImageSharp.Tests/TestImages.cs index fe633fddc..afb13363d 100644 --- a/tests/ImageSharp.Tests/TestImages.cs +++ b/tests/ImageSharp.Tests/TestImages.cs @@ -73,6 +73,8 @@ public static class TestImages public const string DisposeBackgroundRegion = "Png/animated/15-dispose-background-region.png"; public const string DisposePreviousFirst = "Png/animated/12-dispose-prev-first.png"; public const string BlendOverMultiple = "Png/animated/21-blend-over-multiple.png"; + public const string FrameOffset = "Png/animated/frame-offset.png"; + public const string DefaultNotAnimated = "Png/animated/default-not-animated.png"; public const string Issue2666 = "Png/issues/Issue_2666.png"; // Filtered test images from http://www.schaik.com/pngsuite/pngsuite_fil_png.html diff --git a/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_default-not-animated.png/00.png b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_default-not-animated.png/00.png new file mode 100644 index 000000000..4c5ea8169 --- /dev/null +++ b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_default-not-animated.png/00.png @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:8d4716e18655be53630d6d50daebe8c38e0eedb2432c7a73840b55d1473d5944 +size 1050 diff --git a/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_default-not-animated.png/01.png b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_default-not-animated.png/01.png new file mode 100644 index 000000000..790fe45e4 --- /dev/null +++ b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_default-not-animated.png/01.png @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:9b5a6d3cf1a777f6b719c2a1cf79bffe2251355d75e6c0f7ce7a973b3d033419 +size 1177 diff --git a/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/00.png b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/00.png new file mode 100644 index 000000000..870ed61a4 --- /dev/null +++ b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/00.png @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:b85aaf7153e0ca538856a58d7b069bcc13fadc468ea603c85f8782cc691f86c3 +size 387 diff --git a/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/01.png b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/01.png new file mode 100644 index 000000000..cab85d946 --- /dev/null +++ b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/01.png @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:fcb83d6893dcfd869b764ff9846c259eaa0caf26cec3f0fc2cbae2c26f2eeaa5 +size 660 diff --git a/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/02.png b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/02.png new file mode 100644 index 000000000..1a2c5adcf --- /dev/null +++ b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/02.png @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:562ec382f6d2af68e66092bf6949f66147d5f608d3c618eea5a7c1ea400737ff +size 768 diff --git a/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/03.png b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/03.png new file mode 100644 index 000000000..d850459ee --- /dev/null +++ b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/03.png @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:d12a7791b960072e32b78bd9aaf456dc99341eea1c66ea05050433d8c082c6ac +size 579 diff --git a/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/04.png b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/04.png new file mode 100644 index 000000000..000b0567d --- /dev/null +++ b/tests/Images/External/ReferenceOutput/PngDecoderTests/Decode_VerifyAllFrames_Rgba32_frame-offset.png/04.png @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:2db38d7ffcc95c23a5c94a06f10c6cc67406ae581a955c99ede4af97b1a044f8 +size 628 diff --git a/tests/Images/Input/Png/animated/default-not-animated.png b/tests/Images/Input/Png/animated/default-not-animated.png new file mode 100644 index 000000000..1ed72698d --- /dev/null +++ b/tests/Images/Input/Png/animated/default-not-animated.png @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:647d484c8f320b55824b9219270524df3edc434a4793e1627e0ee14af8d6e4f8 +size 1689 diff --git a/tests/Images/Input/Png/animated/frame-offset.png b/tests/Images/Input/Png/animated/frame-offset.png new file mode 100644 index 000000000..4eebb44a3 --- /dev/null +++ b/tests/Images/Input/Png/animated/frame-offset.png @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:3c019073841b48b02cb07c779fed8654c6052aee700e7620d07f5d775d97088f +size 2156