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Pass filtered result scanline by reference.
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Halfs the memory usage
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@JimBobSquarePants
JimBobSquarePants committed Nov 10, 2016
1 parent 502fa2c commit f814dc3
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Showing 5 changed files with 27 additions and 42 deletions.
3 changes: 1 addition & 2 deletions src/ImageSharp/Formats/Png/Filters/AverageFilter.cs
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Expand Up @@ -52,10 +52,9 @@ public static byte[] Decode(byte[] scanline, byte[] previousScanline, int bytesP
/// <param name="bytesPerPixel">The bytes per pixel.</param>
/// <param name="bytesPerScanline">The number of bytes per scanline</param>
/// <returns>The <see cref="T:byte[]"/></returns>
public static byte[] Encode(byte[] scanline, byte[] previousScanline, int bytesPerPixel, int bytesPerScanline)
public static byte[] Encode(byte[] scanline, byte[] previousScanline, byte[] result, int bytesPerPixel, int bytesPerScanline)
{
// Average(x) = Raw(x) - floor((Raw(x-bpp)+Prior(x))/2)
byte[] result = new byte[bytesPerScanline + 1];
fixed (byte* scan = scanline)
fixed (byte* prev = previousScanline)
fixed (byte* res = result)
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6 changes: 1 addition & 5 deletions src/ImageSharp/Formats/Png/Filters/NoneFilter.cs
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Expand Up @@ -30,15 +30,11 @@ public static byte[] Decode(byte[] scanline)
/// </summary>
/// <param name="scanline">The scanline to encode</param>
/// <param name="bytesPerScanline">The number of bytes per scanline</param>
/// <returns>The <see cref="T:byte[]"/></returns>
public static byte[] Encode(byte[] scanline, int bytesPerScanline)
public static void Encode(byte[] scanline, byte[] result, int bytesPerScanline)
{
// Insert a byte before the data.
byte[] result = new byte[bytesPerScanline + 1];
result[0] = 0;
Buffer.BlockCopy(scanline, 0, result, 1, bytesPerScanline);

return result;
}
}
}
4 changes: 1 addition & 3 deletions src/ImageSharp/Formats/Png/Filters/PaethFilter.cs
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Expand Up @@ -52,11 +52,9 @@ public static byte[] Decode(byte[] scanline, byte[] previousScanline, int bytesP
/// <param name="bytesPerPixel">The bytes per pixel.</param>
/// <param name="bytesPerScanline">The number of bytes per scanline</param>
/// <returns>The <see cref="T:byte[]"/></returns>
public static byte[] Encode(byte[] scanline, byte[] previousScanline, int bytesPerPixel, int bytesPerScanline)
public static byte[] Encode(byte[] scanline, byte[] previousScanline, byte[] result, int bytesPerPixel, int bytesPerScanline)
{
// Paeth(x) = Raw(x) - PaethPredictor(Raw(x-bpp), Prior(x), Prior(x - bpp))
byte[] result = new byte[bytesPerScanline + 1];

fixed (byte* scan = scanline)
fixed (byte* prev = previousScanline)
fixed (byte* res = result)
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4 changes: 1 addition & 3 deletions src/ImageSharp/Formats/Png/Filters/UpFilter.cs
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Expand Up @@ -45,11 +45,9 @@ public static byte[] Decode(byte[] scanline, byte[] previousScanline)
/// <param name="bytesPerScanline">The number of bytes per scanline</param>
/// <param name="previousScanline">The previous scanline.</param>
/// <returns>The <see cref="T:byte[]"/></returns>
public static byte[] Encode(byte[] scanline, int bytesPerScanline, byte[] previousScanline)
public static byte[] Encode(byte[] scanline, byte[] previousScanline, byte[] result, int bytesPerScanline)
{
// Up(x) = Raw(x) - Prior(x)
byte[] result = new byte[bytesPerScanline + 1];

fixed (byte* scan = scanline)
fixed (byte* prev = previousScanline)
fixed (byte* res = result)
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52 changes: 23 additions & 29 deletions src/ImageSharp/Formats/Png/PngEncoderCore.cs
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Expand Up @@ -313,9 +313,9 @@ private static void WriteInteger(Stream stream, uint value)
/// <param name="row">The row.</param>
/// <param name="previousScanline">The previous scanline.</param>
/// <param name="rawScanline">The raw scanline.</param>
/// <param name="result">The resultant filtered scanline.</param>
/// <param name="bytesPerScanline">The number of bytes per scanline.</param>
/// <returns>The <see cref="T:byte[]"/></returns>
private byte[] EncodePixelRow<TColor, TPacked>(PixelAccessor<TColor, TPacked> pixels, int row, byte[] previousScanline, byte[] rawScanline, int bytesPerScanline)
private void EncodePixelRow<TColor, TPacked>(PixelAccessor<TColor, TPacked> pixels, int row, byte[] previousScanline, byte[] rawScanline, byte[] result, int bytesPerScanline)
where TColor : struct, IPackedPixel<TPacked>
where TPacked : struct
{
Expand All @@ -333,9 +333,7 @@ private static void WriteInteger(Stream stream, uint value)
break;
}

byte[] filteredScanline = this.GetOptimalFilteredScanline(rawScanline, previousScanline, bytesPerScanline, this.bytesPerPixel);

return filteredScanline;
this.GetOptimalFilteredScanline(rawScanline, previousScanline, result, bytesPerScanline);
}

/// <summary>
Expand All @@ -344,37 +342,30 @@ private static void WriteInteger(Stream stream, uint value)
/// </summary>
/// <param name="rawScanline">The raw scanline</param>
/// <param name="previousScanline">The previous scanline</param>
/// <param name="result">The filtered scanline result</param>
/// <param name="bytesPerScanline">The number of bytes per scanline</param>
/// <param name="bytesPerPixel">The number of bytes per pixel</param>
/// <returns>The <see cref="T:byte[]"/></returns>
private byte[] GetOptimalFilteredScanline(byte[] rawScanline, byte[] previousScanline, int bytesPerScanline, int bytesPerPixel)
private void GetOptimalFilteredScanline(byte[] rawScanline, byte[] previousScanline, byte[] result, int bytesPerScanline)
{
Tuple<byte[], int>[] candidates;

// Palette images don't compress well with adaptive filtering.
if (this.PngColorType == PngColorType.Palette)
{
candidates = new Tuple<byte[], int>[1];

byte[] none = NoneFilter.Encode(rawScanline, bytesPerScanline);
candidates[0] = new Tuple<byte[], int>(none, this.CalculateTotalVariation(none));
NoneFilter.Encode(rawScanline, result, bytesPerScanline);
return;
}
else
{
candidates = new Tuple<byte[], int>[4];

byte[] sub = SubFilter.Encode(rawScanline, bytesPerPixel, bytesPerScanline);
candidates[0] = new Tuple<byte[], int>(sub, this.CalculateTotalVariation(sub));
Tuple<byte[], int>[] candidates = new Tuple<byte[], int>[4];

byte[] up = UpFilter.Encode(rawScanline, bytesPerScanline, previousScanline);
candidates[1] = new Tuple<byte[], int>(up, this.CalculateTotalVariation(up));
byte[] sub = SubFilter.Encode(rawScanline, this.bytesPerPixel, bytesPerScanline);
candidates[0] = new Tuple<byte[], int>(sub, this.CalculateTotalVariation(sub));

byte[] average = AverageFilter.Encode(rawScanline, previousScanline, bytesPerPixel, bytesPerScanline);
candidates[2] = new Tuple<byte[], int>(average, this.CalculateTotalVariation(average));
byte[] up = UpFilter.Encode(rawScanline, previousScanline, result, bytesPerScanline);
candidates[1] = new Tuple<byte[], int>(up, this.CalculateTotalVariation(up));

byte[] paeth = PaethFilter.Encode(rawScanline, previousScanline, bytesPerPixel, bytesPerScanline);
candidates[3] = new Tuple<byte[], int>(paeth, this.CalculateTotalVariation(paeth));
}
byte[] average = AverageFilter.Encode(rawScanline, previousScanline, result, this.bytesPerPixel, bytesPerScanline);
candidates[2] = new Tuple<byte[], int>(average, this.CalculateTotalVariation(average));

byte[] paeth = PaethFilter.Encode(rawScanline, previousScanline, result, this.bytesPerPixel, bytesPerScanline);
candidates[3] = new Tuple<byte[], int>(paeth, this.CalculateTotalVariation(paeth));

int lowestTotalVariation = int.MaxValue;
int lowestTotalVariationIndex = 0;
Expand All @@ -388,7 +379,8 @@ private byte[] GetOptimalFilteredScanline(byte[] rawScanline, byte[] previousSca
}
}

return candidates[lowestTotalVariationIndex].Item1;
// ReSharper disable once RedundantAssignment
result = candidates[lowestTotalVariationIndex].Item1;
}

/// <summary>
Expand Down Expand Up @@ -599,6 +591,7 @@ private void WriteGammaChunk(Stream stream)
int bytesPerScanline = this.width * this.bytesPerPixel;
byte[] previousScanline = ArrayPool<byte>.Shared.Rent(bytesPerScanline);
byte[] rawScanline = ArrayPool<byte>.Shared.Rent(bytesPerScanline);
byte[] result = ArrayPool<byte>.Shared.Rent(bytesPerScanline + 1);

byte[] buffer;
int bufferLength;
Expand All @@ -610,8 +603,8 @@ private void WriteGammaChunk(Stream stream)
{
for (int y = 0; y < this.height; y++)
{
byte[] data = this.EncodePixelRow(pixels, y, previousScanline, rawScanline, bytesPerScanline);
deflateStream.Write(data, 0, data.Length);
this.EncodePixelRow(pixels, y, previousScanline, rawScanline, result, bytesPerScanline);
deflateStream.Write(result, 0, bytesPerScanline + 1);
deflateStream.Flush();

// Do a bit of shuffling;
Expand All @@ -628,6 +621,7 @@ private void WriteGammaChunk(Stream stream)
{
ArrayPool<byte>.Shared.Return(previousScanline);
ArrayPool<byte>.Shared.Return(rawScanline);
ArrayPool<byte>.Shared.Return(result);
memoryStream?.Dispose();
}

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