mirror of https://github.com/SixLabors/ImageSharp
Andrew Wilkinson
9 years ago
6 changed files with 194 additions and 26 deletions
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// <copyright file="WhiteIsZeroTiffColor.cs" company="James Jackson-South">
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// Copyright (c) James Jackson-South and contributors.
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// Licensed under the Apache License, Version 2.0.
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// </copyright>
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namespace ImageSharp.Formats.Tiff |
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{ |
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using System; |
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using System.Numerics; |
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using System.Runtime.CompilerServices; |
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using ImageSharp; |
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using ImageSharp.PixelFormats; |
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/// <summary>
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/// Implements the 'WhiteIsZero' photometric interpretation (for all bit depths).
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/// </summary>
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internal static class WhiteIsZeroTiffColor |
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{ |
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/// <summary>
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/// Decodes pixel data using the current photometric interpretation.
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/// </summary>
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/// <typeparam name="TPixel">The pixel format.</typeparam>
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/// <param name="data">The buffer to read image data from.</param>
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/// <param name="bitsPerSample">The number of bits per sample for each pixel.</param>
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/// <param name="pixels">The image buffer to write pixels to.</param>
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/// <param name="left">The x-coordinate of the left-hand side of the image block.</param>
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/// <param name="top">The y-coordinate of the top of the image block.</param>
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/// <param name="width">The width of the image block.</param>
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/// <param name="height">The height of the image block.</param>
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[MethodImpl(MethodImplOptions.AggressiveInlining)] |
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public static void Decode<TPixel>(byte[] data, uint[] bitsPerSample, PixelAccessor<TPixel> pixels, int left, int top, int width, int height) |
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where TPixel : struct, IPixel<TPixel> |
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{ |
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TPixel color = default(TPixel); |
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BitReader bitReader = new BitReader(data); |
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float factor = (float)Math.Pow(2, bitsPerSample[0]) - 1.0f; |
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for (int y = top; y < top + height; y++) |
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{ |
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for (int x = left; x < left + width; x++) |
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{ |
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int value = bitReader.ReadBits(bitsPerSample[0]); |
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float intensity = 1.0f - (((float)value) / factor); |
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color.PackFromVector4(new Vector4(intensity, intensity, intensity, 1.0f)); |
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pixels[x, y] = color; |
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} |
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bitReader.NextRow(); |
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} |
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} |
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} |
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} |
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// <copyright file="BitReader.cs" company="James Jackson-South">
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// Copyright (c) James Jackson-South and contributors.
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// Licensed under the Apache License, Version 2.0.
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// </copyright>
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namespace ImageSharp.Formats.Tiff |
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{ |
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using System.IO; |
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/// <summary>
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/// Utility class to read a sequence of bits from an array
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/// </summary>
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internal class BitReader |
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{ |
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private readonly byte[] array; |
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private int offset; |
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private int bitOffset; |
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/// <summary>
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/// Initializes a new instance of the <see cref="BitReader" /> class.
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/// </summary>
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/// <param name="array">The array to read data from.</param>
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public BitReader(byte[] array) |
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{ |
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this.array = array; |
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} |
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/// <summary>
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/// Reads the specified number of bits from the array.
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/// </summary>
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/// <param name="bits">The number of bits to read.</param>
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/// <returns>The value read from the array.</returns>
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public int ReadBits(uint bits) |
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{ |
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int value = 0; |
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for (uint i = 0; i < bits; i++) |
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{ |
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int bit = (this.array[this.offset] >> (7 - this.bitOffset)) & 0x01; |
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value = (value << 1) | bit; |
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this.bitOffset++; |
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if (this.bitOffset == 8) |
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{ |
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this.bitOffset = 0; |
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this.offset++; |
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} |
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} |
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return value; |
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} |
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/// <summary>
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/// Moves the reader to the next row of byte-aligned data.
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/// </summary>
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public void NextRow() |
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{ |
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if (this.bitOffset > 0) |
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{ |
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this.bitOffset = 0; |
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this.offset++; |
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} |
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} |
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} |
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} |
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