From c795d8140444b410659b58eed9f960cf1660a08f Mon Sep 17 00:00:00 2001 From: Sven Claesson Date: Tue, 12 May 2026 09:30:50 +0200 Subject: [PATCH] Fix integer overflow and bounds-checking vulnerabilities in EXR decoder (#3126) * Fix integer overflow and bounds-checking vulnerabilities in EXR decoder Use ulong arithmetic in CalculateBytesPerRow and block size calculations to prevent integer overflow. Add validation for DataWindow dimensions, block size limits, and row offsets outside stream bounds. * Harden EXR row offset validation * EXR: validate sizes, prevent overflows, dispose image --------- Co-authored-by: James Jackson-South --- src/ImageSharp/Formats/Exr/ExrDecoderCore.cs | 117 ++++++-- src/ImageSharp/Formats/Exr/ExrEncoderCore.cs | 20 +- src/ImageSharp/Formats/Exr/ExrUtils.cs | 8 +- .../Formats/Exr/ExrDecoderSecurityTests.cs | 274 ++++++++++++++++++ 4 files changed, 384 insertions(+), 35 deletions(-) create mode 100644 tests/ImageSharp.Tests/Formats/Exr/ExrDecoderSecurityTests.cs diff --git a/src/ImageSharp/Formats/Exr/ExrDecoderCore.cs b/src/ImageSharp/Formats/Exr/ExrDecoderCore.cs index 2e60f3a5b9..c24352d576 100644 --- a/src/ImageSharp/Formats/Exr/ExrDecoderCore.cs +++ b/src/ImageSharp/Formats/Exr/ExrDecoderCore.cs @@ -91,6 +91,11 @@ internal sealed class ExrDecoderCore : ImageDecoderCore /// private ExrHeaderAttributes HeaderAttributes { get; set; } + /// + /// Gets or sets the earliest valid stream position for a scanline chunk. + /// + private long MinimumChunkOffset { get; set; } + /// protected override Image Decode(BufferedReadStream stream, CancellationToken cancellationToken) { @@ -100,24 +105,33 @@ internal sealed class ExrDecoderCore : ImageDecoderCore ExrThrowHelper.ThrowNotSupported($"Compression {this.Compression} is not yet supported"); } - Image image = new(this.configuration, this.Width, this.Height, this.metadata); - Buffer2D pixels = image.GetRootFramePixelBuffer(); + Image image = null; + try + { + image = new Image(this.configuration, this.Width, this.Height, this.metadata); + Buffer2D pixels = image.GetRootFramePixelBuffer(); + + switch (this.PixelType) + { + case ExrPixelType.Half: + case ExrPixelType.Float: + this.DecodeFloatingPointPixelData(stream, pixels, cancellationToken); + break; + case ExrPixelType.UnsignedInt: + this.DecodeUnsignedIntPixelData(stream, pixels, cancellationToken); + break; + default: + ExrThrowHelper.ThrowNotSupported("Pixel type is not supported"); + break; + } - switch (this.PixelType) + return image; + } + catch { - case ExrPixelType.Half: - case ExrPixelType.Float: - this.DecodeFloatingPointPixelData(stream, pixels, cancellationToken); - break; - case ExrPixelType.UnsignedInt: - this.DecodeUnsignedIntPixelData(stream, pixels, cancellationToken); - break; - default: - ExrThrowHelper.ThrowNotSupported("Pixel type is not supported"); - break; + image?.Dispose(); + throw; } - - return image; } /// @@ -139,9 +153,14 @@ internal sealed class ExrDecoderCore : ImageDecoderCore where TPixel : unmanaged, IPixel { bool hasAlpha = this.HasAlpha(); - uint bytesPerRow = ExrUtils.CalculateBytesPerRow(this.Channels, (uint)this.Width); + ulong bytesPerRow = ExrUtils.CalculateBytesPerRow(this.Channels, (uint)this.Width); uint rowsPerBlock = ExrUtils.RowsPerBlock(this.Compression); - uint bytesPerBlock = bytesPerRow * rowsPerBlock; + ulong bytesPerBlock = bytesPerRow * rowsPerBlock; + if (bytesPerBlock > int.MaxValue) + { + ExrThrowHelper.ThrowInvalidImageContentException("EXR block size exceeds the maximum allowed size."); + } + int width = this.Width; int height = this.Height; int channelCount = this.Channels.Count; @@ -158,8 +177,8 @@ internal sealed class ExrDecoderCore : ImageDecoderCore this.Compression, this.memoryAllocator, width, - bytesPerBlock, - bytesPerRow, + (uint)bytesPerBlock, + (uint)bytesPerRow, rowsPerBlock, channelCount, this.PixelType); @@ -170,6 +189,7 @@ internal sealed class ExrDecoderCore : ImageDecoderCore ulong rowOffset = this.ReadUnsignedLong(stream); long nextRowOffsetPosition = stream.Position; + this.ValidateChunkOffset(rowOffset, stream); stream.Position = (long)rowOffset; uint rowStartIndex = this.ReadUnsignedInteger(stream); @@ -212,9 +232,14 @@ internal sealed class ExrDecoderCore : ImageDecoderCore where TPixel : unmanaged, IPixel { bool hasAlpha = this.HasAlpha(); - uint bytesPerRow = ExrUtils.CalculateBytesPerRow(this.Channels, (uint)this.Width); + ulong bytesPerRow = ExrUtils.CalculateBytesPerRow(this.Channels, (uint)this.Width); uint rowsPerBlock = ExrUtils.RowsPerBlock(this.Compression); - uint bytesPerBlock = bytesPerRow * rowsPerBlock; + ulong bytesPerBlock = bytesPerRow * rowsPerBlock; + if (bytesPerBlock > int.MaxValue) + { + ExrThrowHelper.ThrowInvalidImageContentException("EXR block size exceeds the maximum allowed size."); + } + int width = this.Width; int height = this.Height; int channelCount = this.Channels.Count; @@ -231,8 +256,8 @@ internal sealed class ExrDecoderCore : ImageDecoderCore this.Compression, this.memoryAllocator, width, - bytesPerBlock, - bytesPerRow, + (uint)bytesPerBlock, + (uint)bytesPerRow, rowsPerBlock, channelCount, this.PixelType); @@ -243,6 +268,7 @@ internal sealed class ExrDecoderCore : ImageDecoderCore ulong rowOffset = this.ReadUnsignedLong(stream); long nextRowOffsetPosition = stream.Position; + this.ValidateChunkOffset(rowOffset, stream); stream.Position = (long)rowOffset; uint rowStartIndex = this.ReadUnsignedInteger(stream); @@ -597,10 +623,38 @@ internal sealed class ExrDecoderCore : ImageDecoderCore this.HeaderAttributes = this.ParseHeaderAttributes(stream); - this.Width = this.HeaderAttributes.DataWindow.XMax - this.HeaderAttributes.DataWindow.XMin + 1; - this.Height = this.HeaderAttributes.DataWindow.YMax - this.HeaderAttributes.DataWindow.YMin + 1; + ExrBox2i dataWindow = this.HeaderAttributes.DataWindow; + if (dataWindow.XMax < dataWindow.XMin || dataWindow.YMax < dataWindow.YMin) + { + ExrThrowHelper.ThrowInvalidImageContentException("EXR DataWindow max values must be greater than or equal to min values."); + } + + long width = (long)dataWindow.XMax - dataWindow.XMin + 1; + long height = (long)dataWindow.YMax - dataWindow.YMin + 1; + + // Decoding stages each row as four color planes, so the width must be bounded + // before later width * 4 buffer sizing can overflow. + if (width > int.MaxValue / 4 || height > int.MaxValue) + { + ExrThrowHelper.ThrowInvalidImageContentException("EXR DataWindow dimensions exceed the maximum allowed size."); + } + + this.Width = (int)width; + this.Height = (int)height; this.Channels = this.HeaderAttributes.Channels; this.Compression = this.HeaderAttributes.Compression; + uint rowsPerBlock = ExrUtils.RowsPerBlock(this.Compression); + long chunkCount = (this.Height + (long)rowsPerBlock - 1) / rowsPerBlock; + long offsetTableByteCount = chunkCount * sizeof(ulong); + + // The scanline offset table sits between the header and pixel chunks; proving it + // fits in the stream keeps all later chunk offsets on the pixel-data side. + if (stream.Position > stream.Length || offsetTableByteCount > stream.Length - stream.Position) + { + ExrThrowHelper.ThrowInvalidImageContentException("EXR chunk offset table is outside the bounds of the stream."); + } + + this.MinimumChunkOffset = stream.Position + offsetTableByteCount; this.PixelType = this.ValidateChannels(); this.ImageDataType = this.DetermineImageDataType(); @@ -866,6 +920,19 @@ internal sealed class ExrDecoderCore : ImageDecoderCore _ => false, }; + /// + /// Validates a scanline chunk offset read from the EXR offset table. + /// + /// The chunk offset to validate. + /// The stream containing the image data. + private void ValidateChunkOffset(ulong chunkOffset, BufferedReadStream stream) + { + if (chunkOffset < (ulong)this.MinimumChunkOffset || chunkOffset >= (ulong)stream.Length) + { + ExrThrowHelper.ThrowInvalidImageContentException("EXR chunk offset is outside the bounds of the stream."); + } + } + /// /// Determines whether this image has alpha channel. /// diff --git a/src/ImageSharp/Formats/Exr/ExrEncoderCore.cs b/src/ImageSharp/Formats/Exr/ExrEncoderCore.cs index e2750d8972..81b7c4da11 100644 --- a/src/ImageSharp/Formats/Exr/ExrEncoderCore.cs +++ b/src/ImageSharp/Formats/Exr/ExrEncoderCore.cs @@ -170,9 +170,13 @@ internal sealed class ExrEncoderCore CancellationToken cancellationToken) where TPixel : unmanaged, IPixel { - uint bytesPerRow = ExrUtils.CalculateBytesPerRow(channels, (uint)width); + ulong bytesPerRow = ExrUtils.CalculateBytesPerRow(channels, (uint)width); uint rowsPerBlock = ExrUtils.RowsPerBlock(compression); - uint bytesPerBlock = bytesPerRow * rowsPerBlock; + ulong bytesPerBlock = bytesPerRow * rowsPerBlock; + if (bytesPerRow > uint.MaxValue || bytesPerBlock > int.MaxValue) + { + throw new ImageFormatException("Image is too large to encode in EXR format."); + } using IMemoryOwner rgbBuffer = this.memoryAllocator.Allocate(width * 4, AllocationOptions.Clean); using IMemoryOwner rowBlockBuffer = this.memoryAllocator.Allocate((int)bytesPerBlock, AllocationOptions.Clean); @@ -181,7 +185,7 @@ internal sealed class ExrEncoderCore Span blueBuffer = rgbBuffer.GetSpan().Slice(width * 2, width); Span alphaBuffer = rgbBuffer.GetSpan().Slice(width * 3, width); - using ExrBaseCompressor compressor = ExrCompressorFactory.Create(compression, this.memoryAllocator, stream, bytesPerBlock, bytesPerRow, rowsPerBlock, width); + using ExrBaseCompressor compressor = ExrCompressorFactory.Create(compression, this.memoryAllocator, stream, (uint)bytesPerBlock, (uint)bytesPerRow, rowsPerBlock, width); ulong[] rowOffsets = new ulong[height]; for (uint y = 0; y < height; y += rowsPerBlock) @@ -262,9 +266,13 @@ internal sealed class ExrEncoderCore CancellationToken cancellationToken) where TPixel : unmanaged, IPixel { - uint bytesPerRow = ExrUtils.CalculateBytesPerRow(channels, (uint)width); + ulong bytesPerRow = ExrUtils.CalculateBytesPerRow(channels, (uint)width); uint rowsPerBlock = ExrUtils.RowsPerBlock(compression); - uint bytesPerBlock = bytesPerRow * rowsPerBlock; + ulong bytesPerBlock = bytesPerRow * rowsPerBlock; + if (bytesPerRow > uint.MaxValue || bytesPerBlock > int.MaxValue) + { + throw new ImageFormatException("Image is too large to encode in EXR format."); + } using IMemoryOwner rgbBuffer = this.memoryAllocator.Allocate(width * 4, AllocationOptions.Clean); using IMemoryOwner rowBlockBuffer = this.memoryAllocator.Allocate((int)bytesPerBlock, AllocationOptions.Clean); @@ -273,7 +281,7 @@ internal sealed class ExrEncoderCore Span blueBuffer = rgbBuffer.GetSpan().Slice(width * 2, width); Span alphaBuffer = rgbBuffer.GetSpan().Slice(width * 3, width); - using ExrBaseCompressor compressor = ExrCompressorFactory.Create(compression, this.memoryAllocator, stream, bytesPerBlock, bytesPerRow, rowsPerBlock, width); + using ExrBaseCompressor compressor = ExrCompressorFactory.Create(compression, this.memoryAllocator, stream, (uint)bytesPerBlock, (uint)bytesPerRow, rowsPerBlock, width); Rgba128 rgb = default; ulong[] rowOffsets = new ulong[height]; diff --git a/src/ImageSharp/Formats/Exr/ExrUtils.cs b/src/ImageSharp/Formats/Exr/ExrUtils.cs index 386210b81d..532950daa9 100644 --- a/src/ImageSharp/Formats/Exr/ExrUtils.cs +++ b/src/ImageSharp/Formats/Exr/ExrUtils.cs @@ -13,9 +13,9 @@ internal static class ExrUtils /// The image channels array. /// The width in pixels of a row. /// The number of bytes per row. - public static uint CalculateBytesPerRow(IList channels, uint width) + public static ulong CalculateBytesPerRow(IList channels, uint width) { - uint bytesPerRow = 0; + ulong bytesPerRow = 0; foreach (ExrChannelInfo channelInfo in channels) { if (channelInfo.ChannelName.Equals("A", StringComparison.Ordinal) @@ -26,11 +26,11 @@ internal static class ExrUtils { if (channelInfo.PixelType == ExrPixelType.Half) { - bytesPerRow += 2 * width; + bytesPerRow += 2UL * width; } else { - bytesPerRow += 4 * width; + bytesPerRow += 4UL * width; } } } diff --git a/tests/ImageSharp.Tests/Formats/Exr/ExrDecoderSecurityTests.cs b/tests/ImageSharp.Tests/Formats/Exr/ExrDecoderSecurityTests.cs new file mode 100644 index 0000000000..2d59c02355 --- /dev/null +++ b/tests/ImageSharp.Tests/Formats/Exr/ExrDecoderSecurityTests.cs @@ -0,0 +1,274 @@ +// Copyright (c) Six Labors. +// Licensed under the Six Labors Split License. + +using System.Buffers.Binary; +using SixLabors.ImageSharp.Formats; +using SixLabors.ImageSharp.Formats.Exr; +using SixLabors.ImageSharp.PixelFormats; + +namespace SixLabors.ImageSharp.Tests.Formats.Exr; + +/// +/// Security regression tests for the EXR decoder (Findings EXR-1, EXR-2, EXR-3). +/// The EXR decoder was merged to main but not yet included in a tagged NuGet release. +/// Each test demonstrates a crafted-input crash present in the unfixed code. +/// +[Trait("Format", "Exr")] +[ValidateDisposedMemoryAllocations] +public class ExrDecoderSecurityTests +{ + /// + /// EXR-1 — EXR DataWindow Integer Overflow Produces Negative Image Dimensions (DoS) + /// + /// Width and Height are computed from attacker-controlled DataWindow attributes + /// using unchecked int subtraction: + /// this.Width = XMax - XMin + 1 // overflows to -2147483647 + /// + /// The negative Width is then passed to the Image<TPixel> constructor, which calls + /// Guard.MustBeGreaterThan(width, 0) → ArgumentOutOfRangeException. + /// + /// After a fix this should throw InvalidImageContentException instead. + /// + /// Affected file: + /// src/ImageSharp/Formats/Exr/ExrDecoderCore.cs lines 600–601 + /// + [Fact] + public void Decode_DataWindowOverflow_NegativeWidth_Throws() + { + // XMin = -1073741825, XMax = 1073741823 + // Width = 1073741823 - (-1073741825) + 1 = 2^31 + 1 → wraps to -2147483647 + byte[] data = BuildMinimalExr(xMin: -1073741825, yMin: 0, xMax: 1073741823, yMax: 0); + + using var stream = new MemoryStream(data); + Assert.Throws( + () => ExrDecoder.Instance.Decode(DecoderOptions.Default, stream)); + } + + /// + /// EXR-2 — EXR Row Offset Table Unvalidated Seek (DoS) + /// + /// Row offsets are read from the file and used unconditionally to seek the stream: + /// ulong rowOffset = this.ReadUnsignedLong(stream); + /// stream.Position = (long)rowOffset; // no bounds check + /// + /// A crafted offset of 0xFFFFFFFFFFFFFFFF casts to −1 as long, causing + /// an ArgumentOutOfRangeException when setting stream.Position. + /// + /// After a fix this should throw InvalidImageContentException instead. + /// + /// Affected file: + /// src/ImageSharp/Formats/Exr/ExrDecoderCore.cs lines 170–175 (scanline) + /// lines 243–248 (tile) + /// + [Fact] + public void Decode_CraftedRowOffsets_OutOfBounds_Throws() + { + // Valid 2×2 image (XMin=0,YMin=0,XMax=1,YMax=1 → Width=2,Height=2). + // Row offset table immediately follows the header null byte: + // 2 rows × 8 bytes each, all set to 0xFFFFFFFFFFFFFFFF. + byte[] invalidOffsets = new byte[16]; + BinaryPrimitives.WriteUInt64LittleEndian(invalidOffsets, 0xFFFFFFFFFFFFFFFF); + BinaryPrimitives.WriteUInt64LittleEndian(invalidOffsets.AsSpan(8), 0xFFFFFFFFFFFFFFFF); + + byte[] data = BuildMinimalExr( + xMin: 0, yMin: 0, xMax: 1, yMax: 1, + rowOffsetTableAppend: invalidOffsets); + + using var stream = new MemoryStream(data); + Assert.Throws( + () => ExrDecoder.Instance.Decode(DecoderOptions.Default, stream)); + } + + [Fact] + public void Decode_CraftedRowOffsets_IntoHeader_Throws() + { + // Offset 0 points back into the EXR file header and must be rejected + // before the decoder seeks to attacker-controlled non-pixel data. + byte[] headerOffsets = new byte[16]; + + byte[] data = BuildMinimalExr( + xMin: 0, yMin: 0, xMax: 1, yMax: 1, + rowOffsetTableAppend: headerOffsets); + + using var stream = new MemoryStream(data); + Assert.Throws( + () => ExrDecoder.Instance.Decode(DecoderOptions.Default, stream)); + } + + [Fact] + public void Decode_CraftedRowOffsets_IntoOffsetTable_Throws() + { + byte[] data = BuildMinimalExr( + xMin: 0, yMin: 0, xMax: 1, yMax: 1, + rowOffsetTableAppend: new byte[16]); + + // Point the first row offset at the second row offset entry. + BinaryPrimitives.WriteUInt64LittleEndian(data.AsSpan(data.Length - 16), (ulong)(data.Length - 8)); + + using var stream = new MemoryStream(data); + Assert.Throws( + () => ExrDecoder.Instance.Decode(DecoderOptions.Default, stream)); + } + + /// + /// EXR-3 — Oversized EXR RGBA row sizing is rejected as invalid image content. + /// + /// With 4 RGBA HALF channels and Width = 2^29, the decoded row staging and + /// bytes-per-row arithmetic both exceed the supported buffer sizing limits. + /// The decoder must reject this as InvalidImageContentException before any allocation. + /// + /// Affected file: + /// src/ImageSharp/Formats/Exr/ExrDecoderCore.cs lines 142–150, 215–223 + /// src/ImageSharp/Formats/Exr/ExrUtils.cs CalculateBytesPerRow + /// + [Fact] + public void Decode_RgbaRowSizingExceedsBufferLimits_Throws() + { + // 4 RGBA HALF channels at this width cannot be represented by the decoder's + // int-sized row staging or block buffers. + byte[] data = BuildMinimalRgbaExr(xMin: 0, yMin: 0, xMax: 536870911, yMax: 0); + + using var stream = new MemoryStream(data); + Assert.Throws( + () => ExrDecoder.Instance.Decode(DecoderOptions.Default, stream)); + } + + [Fact] + public void Decode_DataWindowWidthExceedsRowBufferLimit_Throws() + { + // A single HALF channel keeps bytesPerBlock below int.MaxValue, but the decoder + // still stages four color planes and must reject widths that overflow width × 4. + byte[] data = BuildMinimalExr(xMin: 0, yMin: 0, xMax: int.MaxValue / 4, yMax: 0); + + using var stream = new MemoryStream(data); + Assert.Throws( + () => ExrDecoder.Instance.Decode(DecoderOptions.Default, stream)); + } + + [Fact] + public void Identify_RowOffsetTableExceedsStream_Throws() + { + // Identify parses the header only, so this verifies the offset table bound is + // validated before scanline decoding reads from the table. + byte[] data = BuildMinimalExr(xMin: 0, yMin: 0, xMax: 1, yMax: 1); + + using var stream = new MemoryStream(data); + Assert.Throws( + () => ExrDecoder.Instance.Identify(DecoderOptions.Default, stream)); + } + + // ------------------------------------------------------------------------- + // Helpers: construct minimal valid-enough EXR scanline files. + // + // Required attributes per ParseHeaderAttributes validation: + // channels, compression, dataWindow, displayWindow, + // lineOrder, pixelAspectRatio, screenWindowCenter, screenWindowWidth + // ------------------------------------------------------------------------- + + private static byte[] BuildMinimalExr( + int xMin, int yMin, int xMax, int yMax, + byte[] rowOffsetTableAppend = null) + { + // channels: single "R" HALF channel with xSampling=1, ySampling=1 + // Layout per ReadChannelInfo: name\0 (2) + pixelType (4) + pLinear+reserved (4) + // + xSampling (4) + ySampling (4) = 18 bytes/channel + // + list-null (1) = 19 total + byte[] channelData = + [ + 0x52, 0x00, // "R\0" + 0x01, 0x00, 0x00, 0x00, // pixelType = Half (1) + 0x00, 0x00, 0x00, 0x00, // pLinear + 3 reserved bytes + 0x01, 0x00, 0x00, 0x00, // xSampling = 1 + 0x01, 0x00, 0x00, 0x00, // ySampling = 1 + 0x00, // channel-list null terminator + ]; + + return BuildExrWithChannels(xMin, yMin, xMax, yMax, channelData, rowOffsetTableAppend); + } + + private static byte[] BuildMinimalRgbaExr(int xMin, int yMin, int xMax, int yMax) + { + // 4 HALF channels in alphabetical order (A, B, G, R) per EXR spec. + // 18 bytes per channel × 4 channels + 1 list-null = 73 bytes total. + byte[] channelData = + [ + 0x41, 0x00, // "A\0" + 0x01, 0x00, 0x00, 0x00, // pixelType = Half (1) + 0x00, 0x00, 0x00, 0x00, // pLinear + 3 reserved bytes + 0x01, 0x00, 0x00, 0x00, // xSampling = 1 + 0x01, 0x00, 0x00, 0x00, // ySampling = 1 + 0x42, 0x00, // "B\0" + 0x01, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x00, 0x00, + 0x47, 0x00, // "G\0" + 0x01, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x00, 0x00, + 0x52, 0x00, // "R\0" + 0x01, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x00, 0x00, + 0x01, 0x00, 0x00, 0x00, + 0x00, // channel-list null terminator + ]; + + return BuildExrWithChannels(xMin, yMin, xMax, yMax, channelData); + } + + private static byte[] BuildExrWithChannels( + int xMin, int yMin, int xMax, int yMax, + byte[] channelData, + byte[] rowOffsetTableAppend = null) + { + using var ms = new MemoryStream(); + using var bw = new BinaryWriter(ms, System.Text.Encoding.ASCII, leaveOpen: true); + + // Magic (0x01312F76 LE) + version 2, scanline (flags = 0x00) + bw.Write(new byte[] { 0x76, 0x2F, 0x31, 0x01, 0x02, 0x00, 0x00, 0x00 }); + + void WriteAttr(string name, string type, byte[] payload) + { + foreach (char c in name) bw.Write((byte)c); + bw.Write((byte)0); + foreach (char c in type) bw.Write((byte)c); + bw.Write((byte)0); + bw.Write(payload.Length); + bw.Write(payload); + } + + WriteAttr("channels", "chlist", channelData); + + WriteAttr("compression", "compression", [0x00]); // None + + byte[] dw = new byte[16]; + BinaryPrimitives.WriteInt32LittleEndian(dw, xMin); + BinaryPrimitives.WriteInt32LittleEndian(dw.AsSpan(4), yMin); + BinaryPrimitives.WriteInt32LittleEndian(dw.AsSpan(8), xMax); + BinaryPrimitives.WriteInt32LittleEndian(dw.AsSpan(12), yMax); + WriteAttr("dataWindow", "box2i", dw); + + WriteAttr("displayWindow", "box2i", new byte[16]); // all zeros (0,0,0,0) + + WriteAttr("lineOrder", "lineOrder", [0x00]); // IncreasingY + + byte[] aspect = new byte[4]; + BinaryPrimitives.WriteSingleLittleEndian(aspect, 1.0f); + WriteAttr("pixelAspectRatio", "float", aspect); + + WriteAttr("screenWindowCenter", "v2f", new byte[8]); // (0f, 0f) + + byte[] sww = new byte[4]; + BinaryPrimitives.WriteSingleLittleEndian(sww, 1.0f); + WriteAttr("screenWindowWidth", "float", sww); + + bw.Write((byte)0x00); // end-of-header sentinel + + if (rowOffsetTableAppend is not null) + bw.Write(rowOffsetTableAppend); + + return ms.ToArray(); + } +}