mirror of https://github.com/SixLabors/ImageSharp
James Jackson-South
4 days ago
5 changed files with 926 additions and 8 deletions
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// Copyright (c) Six Labors.
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// Licensed under the Six Labors Split License.
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using SixLabors.ImageSharp.ColorProfiles; |
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namespace SixLabors.ImageSharp.Formats.Heif.Hevc; |
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/// <summary>
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/// Reads the presentation and exposed metadata carried by prefix SEI NAL units for one bounded still picture.
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/// </summary>
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internal sealed class HevcSupplementalEnhancementInformation |
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{ |
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private const int DisplayOrientationPayloadType = 47; |
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private const int MasteringDisplayColorVolumePayloadType = 137; |
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private const int NoDisplayPayloadType = 135; |
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private const int ContentLightLevelPayloadType = 144; |
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private const int AlternativeTransferCharacteristicsPayloadType = 147; |
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private const int AmbientViewingEnvironmentPayloadType = 148; |
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private const int ContentColorVolumePayloadType = 149; |
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/// <summary>
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/// Gets a value indicating whether the selected still picture is marked as unavailable for display.
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/// </summary>
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public bool NoDisplay { get; private set; } |
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/// <summary>
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/// Gets a value indicating whether an active display-orientation message is present.
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/// </summary>
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public bool HasDisplayOrientation { get; private set; } |
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/// <summary>
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/// Gets a value indicating whether the cropped decoded picture is flipped horizontally before rotation.
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/// </summary>
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public bool HorizontalFlip { get; private set; } |
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/// <summary>
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/// Gets a value indicating whether the cropped decoded picture is flipped vertically before rotation.
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/// </summary>
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public bool VerticalFlip { get; private set; } |
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/// <summary>
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/// Gets the unsigned fraction of one complete anticlockwise turn applied after flipping.
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/// </summary>
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public ushort AnticlockwiseRotation { get; private set; } |
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/// <summary>
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/// Gets the preferred CICP transfer-characteristics code, when signaled.
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/// </summary>
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public byte? PreferredTransferCharacteristics { get; private set; } |
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/// <summary>
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/// Gets the content light-level description, when signaled.
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/// </summary>
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public HeifContentLightLevel? ContentLightLevel { get; private set; } |
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/// <summary>
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/// Gets the mastering-display color volume, when signaled.
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/// </summary>
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public HeifMasteringDisplayColorVolume? MasteringDisplayColorVolume { get; private set; } |
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/// <summary>
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/// Gets the content color volume, when signaled and not cancelled.
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/// </summary>
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public HeifContentColorVolume? ContentColorVolume { get; private set; } |
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/// <summary>
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/// Gets the ambient viewing environment, when signaled.
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/// </summary>
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public HeifAmbientViewingEnvironment? AmbientViewingEnvironment { get; private set; } |
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/// <summary>
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/// Reads every byte-aligned message from one prefix SEI RBSP in bitstream order.
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/// </summary>
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/// <param name="rbsp">The decoded NAL payload, including its RBSP trailing byte.</param>
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public void ReadPrefixNalUnit(ReadOnlySpan<byte> rbsp) |
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{ |
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if (rbsp.IsEmpty) |
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{ |
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throw new InvalidImageContentException("The HEVC prefix SEI NAL unit is missing RBSP trailing bits."); |
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} |
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int offset = 0; |
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while (rbsp.Length - offset > 1) |
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{ |
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int payloadType = ReadExtendedValue(rbsp, ref offset, "payload type"); |
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int payloadSize = ReadExtendedValue(rbsp, ref offset, "payload size"); |
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if (payloadSize > rbsp.Length - offset) |
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{ |
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throw new InvalidImageContentException("The HEVC prefix SEI message payload is truncated."); |
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} |
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ReadOnlySpan<byte> payload = rbsp.Slice(offset, payloadSize); |
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offset += payloadSize; |
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switch (payloadType) |
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{ |
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case DisplayOrientationPayloadType: |
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this.ReadDisplayOrientation(payload); |
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break; |
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case NoDisplayPayloadType: |
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this.ReadNoDisplay(payload); |
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break; |
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case MasteringDisplayColorVolumePayloadType: |
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this.ReadMasteringDisplayColorVolume(payload); |
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break; |
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case ContentLightLevelPayloadType: |
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this.ReadContentLightLevel(payload); |
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break; |
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case AlternativeTransferCharacteristicsPayloadType: |
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this.ReadAlternativeTransferCharacteristics(payload); |
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break; |
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case AmbientViewingEnvironmentPayloadType: |
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this.ReadAmbientViewingEnvironment(payload); |
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break; |
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case ContentColorVolumePayloadType: |
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this.ReadContentColorVolume(payload); |
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break; |
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} |
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} |
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if (offset != rbsp.Length - 1 || rbsp[offset] != 0x80) |
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{ |
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throw new InvalidImageContentException("The HEVC prefix SEI NAL unit has invalid RBSP trailing bits."); |
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} |
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} |
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/// <summary>
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/// Reads the legacy HEVC display-orientation payload retained by pinned HM.
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/// </summary>
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private void ReadDisplayOrientation(ReadOnlySpan<byte> payload) |
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{ |
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HevcBitReader reader = new(payload); |
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bool cancel = reader.ReadFlag(); |
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if (cancel) |
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{ |
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this.HasDisplayOrientation = false; |
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this.HorizontalFlip = false; |
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this.VerticalFlip = false; |
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this.AnticlockwiseRotation = 0; |
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ValidatePayloadExtension(ref reader, "display orientation"); |
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return; |
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} |
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this.HorizontalFlip = reader.ReadFlag(); |
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this.VerticalFlip = reader.ReadFlag(); |
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this.AnticlockwiseRotation = (ushort)reader.ReadBits(16); |
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_ = reader.ReadFlag(); |
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ValidatePayloadExtension(ref reader, "display orientation"); |
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this.HasDisplayOrientation = true; |
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} |
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/// <summary>
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/// Records that the selected picture is not intended for display.
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/// </summary>
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private void ReadNoDisplay(ReadOnlySpan<byte> payload) |
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{ |
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// Pinned HM writes no syntax bits for this message, producing a zero-byte payload. A nonempty payload can
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// contain only the generic reserved extension and payload-alignment marker handled by the shared validator.
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ValidateByteAlignedPayloadExtension(payload, "no-display"); |
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this.NoDisplay = true; |
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} |
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/// <summary>
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/// Reads mastering-display metadata in its HEVC fixed-point representation.
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/// </summary>
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private void ReadMasteringDisplayColorVolume(ReadOnlySpan<byte> payload) |
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{ |
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const int syntaxLength = 24; |
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if (payload.Length < syntaxLength) |
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{ |
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throw new InvalidImageContentException("The HEVC mastering-display color-volume SEI payload is truncated."); |
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} |
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this.MasteringDisplayColorVolume = HeifPropertyParser.ParseMasteringDisplayColorVolume(payload[..syntaxLength]); |
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ValidateByteAlignedPayloadExtension(payload[syntaxLength..], "mastering-display color-volume"); |
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} |
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/// <summary>
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/// Reads content light-level metadata in its HEVC fixed-width representation.
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/// </summary>
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private void ReadContentLightLevel(ReadOnlySpan<byte> payload) |
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{ |
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const int syntaxLength = 4; |
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if (payload.Length < syntaxLength) |
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{ |
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throw new InvalidImageContentException("The HEVC content light-level SEI payload is truncated."); |
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} |
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this.ContentLightLevel = HeifPropertyParser.ParseContentLightLevel(payload[..syntaxLength]); |
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ValidateByteAlignedPayloadExtension(payload[syntaxLength..], "content light-level"); |
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} |
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/// <summary>
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/// Reads the preferred transfer function applied when the container does not provide one.
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/// </summary>
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private void ReadAlternativeTransferCharacteristics(ReadOnlySpan<byte> payload) |
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{ |
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if (payload.IsEmpty) |
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{ |
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throw new InvalidImageContentException("The HEVC alternative-transfer-characteristics SEI payload is truncated."); |
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} |
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this.PreferredTransferCharacteristics = payload[0]; |
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ValidateByteAlignedPayloadExtension(payload[1..], "alternative transfer characteristics"); |
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} |
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/// <summary>
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/// Reads the nominal ambient viewing environment.
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/// </summary>
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private void ReadAmbientViewingEnvironment(ReadOnlySpan<byte> payload) |
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{ |
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const int syntaxLength = 8; |
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if (payload.Length < syntaxLength) |
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{ |
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throw new InvalidImageContentException("The HEVC ambient-viewing-environment SEI payload is truncated."); |
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} |
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this.AmbientViewingEnvironment = HeifPropertyParser.ParseAmbientViewingEnvironment(payload[..syntaxLength]); |
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ValidateByteAlignedPayloadExtension(payload[syntaxLength..], "ambient viewing environment"); |
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} |
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/// <summary>
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/// Reads the bit-packed content color-volume syntax and applies cancellation in message order.
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/// </summary>
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private void ReadContentColorVolume(ReadOnlySpan<byte> payload) |
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{ |
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HevcBitReader reader = new(payload); |
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bool cancel = reader.ReadFlag(); |
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if (cancel) |
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{ |
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this.ContentColorVolume = null; |
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ValidatePayloadExtension(ref reader, "content color-volume"); |
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return; |
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} |
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_ = reader.ReadFlag(); |
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bool primariesPresent = reader.ReadFlag(); |
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bool minimumLuminancePresent = reader.ReadFlag(); |
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bool maximumLuminancePresent = reader.ReadFlag(); |
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bool averageLuminancePresent = reader.ReadFlag(); |
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RgbPrimariesChromaticityCoordinates? primaries = null; |
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if (primariesPresent) |
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{ |
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int greenX = unchecked((int)reader.ReadBits(32)); |
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int greenY = unchecked((int)reader.ReadBits(32)); |
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int blueX = unchecked((int)reader.ReadBits(32)); |
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int blueY = unchecked((int)reader.ReadBits(32)); |
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int redX = unchecked((int)reader.ReadBits(32)); |
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int redY = unchecked((int)reader.ReadBits(32)); |
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const int maximumChromaticityValue = 5_000_000; |
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if (greenX is < -maximumChromaticityValue or > maximumChromaticityValue |
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|| greenY is < -maximumChromaticityValue or > maximumChromaticityValue |
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|| blueX is < -maximumChromaticityValue or > maximumChromaticityValue |
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|| blueY is < -maximumChromaticityValue or > maximumChromaticityValue |
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|| redX is < -maximumChromaticityValue or > maximumChromaticityValue |
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|| redY is < -maximumChromaticityValue or > maximumChromaticityValue) |
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{ |
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throw new InvalidImageContentException("The HEVC content color-volume SEI payload has an out-of-range primary coordinate."); |
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} |
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const float chromaticityScale = 1F / 50000F; |
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// H.274 stores signed primary coordinates in G, B, R order. Reorder them once at the codec boundary so
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// the retained value has the same observable RGB coordinate contract as the equivalent item property.
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primaries = new RgbPrimariesChromaticityCoordinates( |
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new CieXyChromaticityCoordinates(redX * chromaticityScale, redY * chromaticityScale), |
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new CieXyChromaticityCoordinates(greenX * chromaticityScale, greenY * chromaticityScale), |
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new CieXyChromaticityCoordinates(blueX * chromaticityScale, blueY * chromaticityScale)); |
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} |
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uint? minimumLuminance = minimumLuminancePresent ? reader.ReadBits(32) : null; |
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uint? maximumLuminance = maximumLuminancePresent ? reader.ReadBits(32) : null; |
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uint? averageLuminance = averageLuminancePresent ? reader.ReadBits(32) : null; |
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if ((minimumLuminance is not null && averageLuminance is not null && minimumLuminance.Value > averageLuminance.Value) |
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|| (averageLuminance is not null && maximumLuminance is not null && averageLuminance.Value > maximumLuminance.Value) |
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|| (minimumLuminance is not null && maximumLuminance is not null && minimumLuminance.Value > maximumLuminance.Value)) |
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{ |
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throw new InvalidImageContentException("The HEVC content color-volume SEI luminance values are not in ascending order."); |
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} |
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ValidatePayloadExtension(ref reader, "content color-volume"); |
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const double luminanceScale = 1D / 10000000D; |
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this.ContentColorVolume = new HeifContentColorVolume( |
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primaries, |
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minimumLuminance * luminanceScale, |
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maximumLuminance * luminanceScale, |
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averageLuminance * luminanceScale); |
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} |
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/// <summary>
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/// Reads an extended SEI payload type or size whose continuation bytes are all 255.
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/// </summary>
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private static int ReadExtendedValue(ReadOnlySpan<byte> data, ref int offset, string valueName) |
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{ |
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int value = 0; |
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while (true) |
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{ |
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if ((uint)offset >= (uint)data.Length) |
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{ |
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throw new InvalidImageContentException($"The HEVC prefix SEI {valueName} is truncated."); |
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} |
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int current = data[offset++]; |
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if (value > int.MaxValue - current) |
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{ |
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throw new InvalidImageContentException($"The HEVC prefix SEI {valueName} is too large."); |
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} |
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value += current; |
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if (current != byte.MaxValue) |
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{ |
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return value; |
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} |
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} |
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} |
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/// <summary>
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/// Validates an optional extension following fixed byte-aligned SEI syntax.
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/// </summary>
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private static void ValidateByteAlignedPayloadExtension(ReadOnlySpan<byte> extension, string payloadName) |
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{ |
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if (extension.IsEmpty) |
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{ |
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return; |
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} |
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HevcBitReader reader = new(extension); |
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ValidatePayloadExtension(ref reader, payloadName); |
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} |
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/// <summary>
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/// Validates reserved payload-extension data followed by its final one bit and zero padding.
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/// </summary>
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private static void ValidatePayloadExtension(ref HevcBitReader reader, string payloadName) |
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{ |
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bool foundMarker = false; |
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while (reader.BitsRemaining > 0) |
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{ |
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foundMarker |= reader.ReadFlag(); |
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} |
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// The final set bit is payload_bit_equal_to_one; any preceding bits are the reserved extension data that
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// pinned HM deliberately skips. An all-zero remainder has no marker and is therefore not a complete payload.
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if (!foundMarker) |
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{ |
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throw new InvalidImageContentException($"The HEVC {payloadName} SEI payload has invalid trailing bits."); |
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} |
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} |
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} |
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