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Express readonly intent in Span parameters

af/merge-core
Jason Nelson 8 years ago
parent
997ca49679
commit
915b707fa4
2 changed files with 22 additions and 28 deletions
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  1. 33
      src/ImageSharp/Formats/Png/PngDecoderCore.cs
  2. 17
      src/ImageSharp/Formats/Png/PngEncoderCore.cs

33
src/ImageSharp/Formats/Png/PngDecoderCore.cs
View File

@ -349,13 +349,12 @@ namespace SixLabors.ImageSharp.Formats.Png
/// <summary>
/// Converts a byte array to a new array where each value in the original array is represented by the specified number of bits.
/// </summary>
/// <param name="source">The bytes to convert from. Cannot be null.</param>
/// <param name="source">The bytes to convert from. Cannot be empty.</param>
/// <param name="bytesPerScanline">The number of bytes per scanline</param>
/// <param name="bits">The number of bits per value.</param>
/// <returns>The resulting <see cref="Span{Byte}"/> array. Is never null.</returns>
/// <exception cref="System.ArgumentNullException"><paramref name="source"/> is null.</exception>
/// <returns>The resulting <see cref="ReadOnlySpan{Byte}"/> array.</returns>
/// <exception cref="System.ArgumentException"><paramref name="bits"/> is less than or equals than zero.</exception>
private static Span<byte> ToArrayByBitsLength(Span<byte> source, int bytesPerScanline, int bits)
private static ReadOnlySpan<byte> ToArrayByBitsLength(ReadOnlySpan<byte> source, int bytesPerScanline, int bits)
{
Guard.MustBeGreaterThan(source.Length, 0, nameof(source));
Guard.MustBeGreaterThan(bits, 0, nameof(bits));
@ -669,7 +668,7 @@ namespace SixLabors.ImageSharp.Formats.Png
}
Span<TPixel> rowSpan = image.GetPixelRowSpan(this.currentRow);
this.ProcessInterlacedDefilteredScanline(this.scanline.Array, rowSpan, Adam7FirstColumn[this.pass], Adam7ColumnIncrement[this.pass]);
this.ProcessInterlacedDefilteredScanline(this.scanline.Span, rowSpan, Adam7FirstColumn[this.pass], Adam7ColumnIncrement[this.pass]);
this.SwapBuffers();
@ -697,20 +696,20 @@ namespace SixLabors.ImageSharp.Formats.Png
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="defilteredScanline">The de-filtered scanline</param>
/// <param name="pixels">The image</param>
private void ProcessDefilteredScanline<TPixel>(Span<byte> defilteredScanline, ImageFrame<TPixel> pixels)
private void ProcessDefilteredScanline<TPixel>(ReadOnlySpan<byte> defilteredScanline, ImageFrame<TPixel> pixels)
where TPixel : struct, IPixel<TPixel>
{
var color = default(TPixel);
Span<TPixel> rowSpan = pixels.GetPixelRowSpan(this.currentRow);
// Trim the first marker byte from the buffer
Span<byte> scanlineBuffer = defilteredScanline.Slice(1, defilteredScanline.Length - 1);
ReadOnlySpan<byte> scanlineBuffer = defilteredScanline.Slice(1, defilteredScanline.Length - 1);
switch (this.pngColorType)
{
case PngColorType.Grayscale:
int factor = 255 / ((int)Math.Pow(2, this.header.BitDepth) - 1);
Span<byte> newScanline1 = ToArrayByBitsLength(scanlineBuffer, this.bytesPerScanline, this.header.BitDepth);
ReadOnlySpan<byte> newScanline1 = ToArrayByBitsLength(scanlineBuffer, this.bytesPerScanline, this.header.BitDepth);
for (int x = 0; x < this.header.Width; x++)
{
@ -794,10 +793,10 @@ namespace SixLabors.ImageSharp.Formats.Png
}
else
{
Span<Rgb24> rgb24Span = scanlineBuffer.NonPortableCast<byte, Rgb24>();
ReadOnlySpan<Rgb24> rgb24Span = scanlineBuffer.NonPortableCast<byte, Rgb24>();
for (int x = 0; x < this.header.Width; x++)
{
ref Rgb24 rgb24 = ref rgb24Span[x];
ref readonly Rgb24 rgb24 = ref rgb24Span[x];
var rgba32 = default(Rgba32);
rgba32.Rgb = rgb24;
rgba32.A = (byte)(rgb24.Equals(this.rgb24Trans) ? 0 : 255);
@ -838,7 +837,7 @@ namespace SixLabors.ImageSharp.Formats.Png
/// <param name="target">The target buffer</param>
/// <param name="length">The target length</param>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private void From16BitTo8Bit(Span<byte> source, Span<byte> target, int length)
private void From16BitTo8Bit(ReadOnlySpan<byte> source, Span<byte> target, int length)
{
for (int i = 0, j = 0; i < length; i++, j += 2)
{
@ -879,10 +878,10 @@ namespace SixLabors.ImageSharp.Formats.Png
/// <typeparam name="TPixel">The type of pixel we are expanding to</typeparam>
/// <param name="defilteredScanline">The scanline</param>
/// <param name="row">Thecurrent output image row</param>
private void ProcessScanlineFromPalette<TPixel>(Span<byte> defilteredScanline, Span<TPixel> row)
private void ProcessScanlineFromPalette<TPixel>(ReadOnlySpan<byte> defilteredScanline, Span<TPixel> row)
where TPixel : struct, IPixel<TPixel>
{
Span<byte> newScanline = ToArrayByBitsLength(defilteredScanline, this.bytesPerScanline, this.header.BitDepth);
ReadOnlySpan<byte> newScanline = ToArrayByBitsLength(defilteredScanline, this.bytesPerScanline, this.header.BitDepth);
byte[] pal = this.palette;
var color = default(TPixel);
@ -929,19 +928,19 @@ namespace SixLabors.ImageSharp.Formats.Png
/// <param name="rowSpan">The current image row.</param>
/// <param name="pixelOffset">The column start index. Always 0 for none interlaced images.</param>
/// <param name="increment">The column increment. Always 1 for none interlaced images.</param>
private void ProcessInterlacedDefilteredScanline<TPixel>(byte[] defilteredScanline, Span<TPixel> rowSpan, int pixelOffset = 0, int increment = 1)
private void ProcessInterlacedDefilteredScanline<TPixel>(ReadOnlySpan<byte> defilteredScanline, Span<TPixel> rowSpan, int pixelOffset = 0, int increment = 1)
where TPixel : struct, IPixel<TPixel>
{
var color = default(TPixel);
// Trim the first marker byte from the buffer
var scanlineBuffer = new Span<byte>(defilteredScanline, 1, defilteredScanline.Length - 1);
ReadOnlySpan<byte> scanlineBuffer = defilteredScanline.Slice(1, defilteredScanline.Length - 1);
switch (this.pngColorType)
{
case PngColorType.Grayscale:
int factor = 255 / ((int)Math.Pow(2, this.header.BitDepth) - 1);
Span<byte> newScanline1 = ToArrayByBitsLength(scanlineBuffer, this.bytesPerScanline, this.header.BitDepth);
ReadOnlySpan<byte> newScanline1 = ToArrayByBitsLength(scanlineBuffer, this.bytesPerScanline, this.header.BitDepth);
for (int x = pixelOffset, o = 0; x < this.header.Width; x += increment, o++)
{
@ -974,7 +973,7 @@ namespace SixLabors.ImageSharp.Formats.Png
case PngColorType.Palette:
Span<byte> newScanline = ToArrayByBitsLength(scanlineBuffer, this.bytesPerScanline, this.header.BitDepth);
ReadOnlySpan<byte> newScanline = ToArrayByBitsLength(scanlineBuffer, this.bytesPerScanline, this.header.BitDepth);
var rgba = default(Rgba32);
if (this.paletteAlpha != null && this.paletteAlpha.Length > 0)

17
src/ImageSharp/Formats/Png/PngEncoderCore.cs
View File

@ -255,7 +255,7 @@ namespace SixLabors.ImageSharp.Formats.Png
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="rowSpan">The image row span.</param>
private void CollectGrayscaleBytes<TPixel>(Span<TPixel> rowSpan)
private void CollectGrayscaleBytes<TPixel>(ReadOnlySpan<TPixel> rowSpan)
where TPixel : struct, IPixel<TPixel>
{
byte[] rawScanlineArray = this.rawScanline.Array;
@ -290,7 +290,7 @@ namespace SixLabors.ImageSharp.Formats.Png
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="rowSpan">The row span.</param>
private void CollecTPixelBytes<TPixel>(Span<TPixel> rowSpan)
private void CollecTPixelBytes<TPixel>(ReadOnlySpan<TPixel> rowSpan)
where TPixel : struct, IPixel<TPixel>
{
if (this.bytesPerPixel == 4)
@ -311,7 +311,7 @@ namespace SixLabors.ImageSharp.Formats.Png
/// <param name="rowSpan">The row span.</param>
/// <param name="row">The row.</param>
/// <returns>The <see cref="T:byte[]"/></returns>
private IManagedByteBuffer EncodePixelRow<TPixel>(Span<TPixel> rowSpan, int row)
private IManagedByteBuffer EncodePixelRow<TPixel>(ReadOnlySpan<TPixel> rowSpan, int row)
where TPixel : struct, IPixel<TPixel>
{
switch (this.pngColorType)
@ -554,15 +554,14 @@ namespace SixLabors.ImageSharp.Formats.Png
byte[] buffer;
int bufferLength;
MemoryStream memoryStream = null;
try
using (var memoryStream = new MemoryStream())
{
memoryStream = new MemoryStream();
using (var deflateStream = new ZlibDeflateStream(memoryStream, this.compressionLevel))
{
for (int y = 0; y < this.height; y++)
{
IManagedByteBuffer r = this.EncodePixelRow(pixels.GetPixelRowSpan(y), y);
IManagedByteBuffer r = this.EncodePixelRow(pixels.GetPixelRowSpan(y).AsReadOnlySpan(), y);
deflateStream.Write(r.Array, 0, resultLength);
IManagedByteBuffer temp = this.rawScanline;
@ -574,10 +573,6 @@ namespace SixLabors.ImageSharp.Formats.Png
buffer = memoryStream.ToArray();
bufferLength = buffer.Length;
}
finally
{
memoryStream?.Dispose();
}
// Store the chunks in repeated 64k blocks.
// This reduces the memory load for decoding the image for many decoders.

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