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Merge pull request #1798 from SixLabors/bp/webpexifwithpadding
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Write exif profile with padding if needed
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@JimBobSquarePants
JimBobSquarePants committed Oct 30, 2021
2 parents b401937 + 7f3c8ff commit 527e0fb
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Showing 7 changed files with 104 additions and 39 deletions.
67 changes: 47 additions & 20 deletions src/ImageSharp/Formats/Webp/BitWriter/BitWriterBase.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,11 +10,22 @@ namespace SixLabors.ImageSharp.Formats.Webp.BitWriter
{
internal abstract class BitWriterBase
{
private const uint MaxDimension = 16777215;

private const ulong MaxCanvasPixels = 4294967295ul;

protected const uint ExtendedFileChunkSize = WebpConstants.ChunkHeaderSize + WebpConstants.Vp8XChunkSize;

/// <summary>
/// Buffer to write to.
/// </summary>
private byte[] buffer;

/// <summary>
/// A scratch buffer to reduce allocations.
/// </summary>
private readonly byte[] scratchBuffer = new byte[4];

/// <summary>
/// Initializes a new instance of the <see cref="BitWriterBase"/> class.
/// </summary>
Expand Down Expand Up @@ -52,15 +63,6 @@ internal abstract class BitWriterBase
/// </summary>
public abstract void Finish();

/// <summary>
/// Writes the encoded image to the stream.
/// </summary>
/// <param name="stream">The stream to write to.</param>
/// <param name="exifProfile">The exif profile.</param>
/// <param name="width">The width of the image.</param>
/// <param name="height">The height of the image.</param>
public abstract void WriteEncodedImageToStream(Stream stream, ExifProfile exifProfile, uint width, uint height);

protected void ResizeBuffer(int maxBytes, int sizeRequired)
{
int newSize = (3 * maxBytes) >> 1;
Expand All @@ -81,13 +83,25 @@ protected void ResizeBuffer(int maxBytes, int sizeRequired)
/// <param name="riffSize">The block length.</param>
protected void WriteRiffHeader(Stream stream, uint riffSize)
{
Span<byte> buf = stackalloc byte[4];
stream.Write(WebpConstants.RiffFourCc);
BinaryPrimitives.WriteUInt32LittleEndian(buf, riffSize);
stream.Write(buf);
BinaryPrimitives.WriteUInt32LittleEndian(this.scratchBuffer, riffSize);
stream.Write(this.scratchBuffer.AsSpan(0, 4));
stream.Write(WebpConstants.WebpHeader);
}

/// <summary>
/// Calculates the exif chunk size.
/// </summary>
/// <param name="exifBytes">The exif profile bytes.</param>
/// <returns>The exif chunk size in bytes.</returns>
protected uint ExifChunkSize(byte[] exifBytes)
{
uint exifSize = (uint)exifBytes.Length;
uint exifChunkSize = WebpConstants.ChunkHeaderSize + exifSize + (exifSize & 1);

return exifChunkSize;
}

/// <summary>
/// Writes the Exif profile to the stream.
/// </summary>
Expand All @@ -97,12 +111,19 @@ protected void WriteExifProfile(Stream stream, byte[] exifBytes)
{
DebugGuard.NotNull(exifBytes, nameof(exifBytes));

Span<byte> buf = stackalloc byte[4];
uint size = (uint)exifBytes.Length;
Span<byte> buf = this.scratchBuffer.AsSpan(0, 4);
BinaryPrimitives.WriteUInt32BigEndian(buf, (uint)WebpChunkType.Exif);
stream.Write(buf);
BinaryPrimitives.WriteUInt32LittleEndian(buf, (uint)exifBytes.Length);
BinaryPrimitives.WriteUInt32LittleEndian(buf, size);
stream.Write(buf);
stream.Write(exifBytes);

// Add padding byte if needed.
if ((size & 1) == 1)
{
stream.WriteByte(0);
}
}

/// <summary>
Expand All @@ -112,16 +133,16 @@ protected void WriteExifProfile(Stream stream, byte[] exifBytes)
/// <param name="exifProfile">A exif profile or null, if it does not exist.</param>
/// <param name="width">The width of the image.</param>
/// <param name="height">The height of the image.</param>
protected void WriteVp8XHeader(Stream stream, ExifProfile exifProfile, uint width, uint height)
/// <param name="hasAlpha">Flag indicating, if a alpha channel is present.</param>
protected void WriteVp8XHeader(Stream stream, ExifProfile exifProfile, uint width, uint height, bool hasAlpha)
{
int maxDimension = 16777215;
if (width > maxDimension || height > maxDimension)
if (width > MaxDimension || height > MaxDimension)
{
WebpThrowHelper.ThrowInvalidImageDimensions($"Image width or height exceeds maximum allowed dimension of {maxDimension}");
WebpThrowHelper.ThrowInvalidImageDimensions($"Image width or height exceeds maximum allowed dimension of {MaxDimension}");
}

// The spec states that the product of Canvas Width and Canvas Height MUST be at most 2^32 - 1.
if (width * height > 4294967295ul)
if (width * height > MaxCanvasPixels)
{
WebpThrowHelper.ThrowInvalidImageDimensions("The product of image width and height MUST be at most 2^32 - 1");
}
Expand All @@ -133,7 +154,13 @@ protected void WriteVp8XHeader(Stream stream, ExifProfile exifProfile, uint widt
flags |= 8;
}

Span<byte> buf = stackalloc byte[4];
if (hasAlpha)
{
// Set alpha bit.
flags |= 16;
}

Span<byte> buf = this.scratchBuffer.AsSpan(0, 4);
stream.Write(WebpConstants.Vp8XMagicBytes);
BinaryPrimitives.WriteUInt32LittleEndian(buf, WebpConstants.Vp8XChunkSize);
stream.Write(buf);
Expand Down
21 changes: 14 additions & 7 deletions src/ImageSharp/Formats/Webp/BitWriter/Vp8BitWriter.cs
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Expand Up @@ -399,18 +399,25 @@ private void Flush()
}
}

/// <inheritdoc/>
public override void WriteEncodedImageToStream(Stream stream, ExifProfile exifProfile, uint width, uint height)
/// <summary>
/// Writes the encoded image to the stream.
/// </summary>
/// <param name="stream">The stream to write to.</param>
/// <param name="exifProfile">The exif profile.</param>
/// <param name="width">The width of the image.</param>
/// <param name="height">The height of the image.</param>
/// <param name="hasAlpha">Flag indicating, if a alpha channel is present.</param>
public void WriteEncodedImageToStream(Stream stream, ExifProfile exifProfile, uint width, uint height, bool hasAlpha)
{
bool isVp8X = false;
byte[] exifBytes = null;
uint riffSize = 0;
if (exifProfile != null)
{
isVp8X = true;
riffSize += WebpConstants.ChunkHeaderSize + WebpConstants.Vp8XChunkSize;
riffSize += ExtendedFileChunkSize;
exifBytes = exifProfile.ToByteArray();
riffSize += WebpConstants.ChunkHeaderSize + (uint)exifBytes.Length;
riffSize += this.ExifChunkSize(exifBytes);
}

this.Finish();
Expand All @@ -433,7 +440,7 @@ public override void WriteEncodedImageToStream(Stream stream, ExifProfile exifPr
riffSize += WebpConstants.TagSize + WebpConstants.ChunkHeaderSize + vp8Size;

// Emit headers and partition #0
this.WriteWebpHeaders(stream, size0, vp8Size, riffSize, isVp8X, width, height, exifProfile);
this.WriteWebpHeaders(stream, size0, vp8Size, riffSize, isVp8X, width, height, exifProfile, hasAlpha);
bitWriterPartZero.WriteToStream(stream);

// Write the encoded image to the stream.
Expand Down Expand Up @@ -616,14 +623,14 @@ private void CodeIntraModes(Vp8BitWriter bitWriter)
while (it.Next());
}

private void WriteWebpHeaders(Stream stream, uint size0, uint vp8Size, uint riffSize, bool isVp8X, uint width, uint height, ExifProfile exifProfile)
private void WriteWebpHeaders(Stream stream, uint size0, uint vp8Size, uint riffSize, bool isVp8X, uint width, uint height, ExifProfile exifProfile, bool hasAlpha)
{
this.WriteRiffHeader(stream, riffSize);

// Write VP8X, header if necessary.
if (isVp8X)
{
this.WriteVp8XHeader(stream, exifProfile, width, height);
this.WriteVp8XHeader(stream, exifProfile, width, height, hasAlpha);
}

this.WriteVp8Header(stream, vp8Size);
Expand Down
22 changes: 14 additions & 8 deletions src/ImageSharp/Formats/Webp/BitWriter/Vp8LBitWriter.cs
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Expand Up @@ -127,19 +127,25 @@ public override void Finish()
this.used = 0;
}

/// <inheritdoc/>
public override void WriteEncodedImageToStream(Stream stream, ExifProfile exifProfile, uint width, uint height)
/// <summary>
/// Writes the encoded image to the stream.
/// </summary>
/// <param name="stream">The stream to write to.</param>
/// <param name="exifProfile">The exif profile.</param>
/// <param name="width">The width of the image.</param>
/// <param name="height">The height of the image.</param>
/// <param name="hasAlpha">Flag indicating, if a alpha channel is present.</param>
public void WriteEncodedImageToStream(Stream stream, ExifProfile exifProfile, uint width, uint height, bool hasAlpha)
{
Span<byte> buffer = stackalloc byte[4];
bool isVp8X = false;
byte[] exifBytes = null;
uint riffSize = 0;
if (exifProfile != null)
{
isVp8X = true;
riffSize += WebpConstants.ChunkHeaderSize + WebpConstants.Vp8XChunkSize;
riffSize += ExtendedFileChunkSize;
exifBytes = exifProfile.ToByteArray();
riffSize += WebpConstants.ChunkHeaderSize + (uint)exifBytes.Length;
riffSize += this.ExifChunkSize(exifBytes);
}

this.Finish();
Expand All @@ -154,15 +160,15 @@ public override void WriteEncodedImageToStream(Stream stream, ExifProfile exifPr
// Write VP8X, header if necessary.
if (isVp8X)
{
this.WriteVp8XHeader(stream, exifProfile, width, height);
this.WriteVp8XHeader(stream, exifProfile, width, height, hasAlpha);
}

// Write magic bytes indicating its a lossless webp.
stream.Write(WebpConstants.Vp8LMagicBytes);

// Write Vp8 Header.
BinaryPrimitives.WriteUInt32LittleEndian(buffer, size);
stream.Write(buffer);
BinaryPrimitives.WriteUInt32LittleEndian(this.scratchBuffer, size);
stream.Write(this.scratchBuffer.AsSpan(0, 4));
stream.WriteByte(WebpConstants.Vp8LHeaderMagicByte);

// Write the encoded bytes of the image to the stream.
Expand Down
2 changes: 1 addition & 1 deletion src/ImageSharp/Formats/Webp/Lossless/Vp8LEncoder.cs
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Expand Up @@ -234,7 +234,7 @@ public void Encode<TPixel>(Image<TPixel> image, Stream stream)
this.EncodeStream(image);

// Write bytes from the bitwriter buffer to the stream.
this.bitWriter.WriteEncodedImageToStream(stream, image.Metadata.ExifProfile, (uint)width, (uint)height);
this.bitWriter.WriteEncodedImageToStream(stream, image.Metadata.ExifProfile, (uint)width, (uint)height, hasAlpha);
}

/// <summary>
Expand Down
4 changes: 3 additions & 1 deletion src/ImageSharp/Formats/Webp/Lossy/Vp8Encoder.cs
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Expand Up @@ -317,6 +317,8 @@ public void Encode<TPixel>(Image<TPixel> image, Stream stream)
this.bitWriter = new Vp8BitWriter(expectedSize, this);

// TODO: EncodeAlpha();
bool hasAlpha = false;

// Stats-collection loop.
this.StatLoop(width, height, yStride, uvStride);
it.Init();
Expand Down Expand Up @@ -348,7 +350,7 @@ public void Encode<TPixel>(Image<TPixel> image, Stream stream)

// Write bytes from the bitwriter buffer to the stream.
image.Metadata.SyncProfiles();
this.bitWriter.WriteEncodedImageToStream(stream, image.Metadata.ExifProfile, (uint)width, (uint)height);
this.bitWriter.WriteEncodedImageToStream(stream, image.Metadata.ExifProfile, (uint)width, (uint)height, hasAlpha);
}

/// <inheritdoc/>
Expand Down
2 changes: 0 additions & 2 deletions src/ImageSharp/Formats/Webp/WebpEncoderCore.cs
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Expand Up @@ -4,11 +4,9 @@
using System.IO;
using System.Threading;
using SixLabors.ImageSharp.Advanced;
using SixLabors.ImageSharp.Formats.Bmp;
using SixLabors.ImageSharp.Formats.Webp.Lossless;
using SixLabors.ImageSharp.Formats.Webp.Lossy;
using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.Metadata;
using SixLabors.ImageSharp.PixelFormats;

namespace SixLabors.ImageSharp.Formats.Webp
Expand Down
25 changes: 25 additions & 0 deletions tests/ImageSharp.Tests/Formats/WebP/WebpMetaDataTests.cs
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Expand Up @@ -63,6 +63,31 @@ public void IgnoreMetadata_ControlsWhetherIccpIsParsed<TPixel>(TestImageProvider
}
}

[Theory]
[InlineData(WebpFileFormatType.Lossy)]
[InlineData(WebpFileFormatType.Lossless)]
public void Encode_WritesExifWithPadding(WebpFileFormatType fileFormatType)
{
// arrange
using var input = new Image<Rgba32>(25, 25);
using var memoryStream = new MemoryStream();
var expectedExif = new ExifProfile();
string expectedSoftware = "ImageSharp";
expectedExif.SetValue(ExifTag.Software, expectedSoftware);
input.Metadata.ExifProfile = expectedExif;

// act
input.Save(memoryStream, new WebpEncoder() { FileFormat = fileFormatType });
memoryStream.Position = 0;

// assert
using var image = Image.Load<Rgba32>(memoryStream);
ExifProfile actualExif = image.Metadata.ExifProfile;
Assert.NotNull(actualExif);
Assert.Equal(expectedExif.Values.Count, actualExif.Values.Count);
Assert.Equal(expectedSoftware, actualExif.GetValue(ExifTag.Software).Value);
}

[Theory]
[WithFile(TestImages.Webp.Lossy.WithExif, PixelTypes.Rgba32)]
public void EncodeLossyWebp_PreservesExif<TPixel>(TestImageProvider<TPixel> provider)
Expand Down

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