mirror of https://github.com/SixLabors/ImageSharp
Anton Firszov
9 years ago
6 changed files with 197 additions and 106 deletions
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// <copyright file="JpegBlockProcessor.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.Jpg |
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{ |
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using System.Runtime.CompilerServices; |
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using System.Runtime.InteropServices; |
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/// <summary>
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/// Encapsulates the implementation of processing "raw" <see cref="DecodedBlockArray"/>-s into Jpeg image channels.
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/// </summary>
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[StructLayout(LayoutKind.Sequential)] |
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internal unsafe struct JpegBlockProcessor |
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{ |
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/// <summary>
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/// The <see cref="ComputationData"/>
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/// </summary>
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private ComputationData data; |
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/// <summary>
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/// Pointers to elements of <see cref="data"/>
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/// </summary>
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private DataPointers pointers; |
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/// <summary>
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/// The component index.
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/// </summary>
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private int componentIndex; |
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/// <summary>
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/// Initialize the <see cref="JpegBlockProcessor"/> instance on the stack.
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/// </summary>
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/// <param name="processor">The <see cref="JpegBlockProcessor"/> instance</param>
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/// <param name="componentIndex">The current component index</param>
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public static void Init(JpegBlockProcessor* processor, int componentIndex) |
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{ |
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processor->componentIndex = componentIndex; |
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processor->data = ComputationData.Create(); |
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processor->pointers = new DataPointers(&processor->data); |
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} |
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/// <summary>
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/// Dequantize, perform the inverse DCT and store the blocks to the into the corresponding <see cref="JpegPixelArea"/> instances.
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/// </summary>
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/// <param name="decoder">The <see cref="JpegDecoderCore"/> instance</param>
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public void ProcessAllBlocks(JpegDecoderCore decoder) |
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{ |
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DecodedBlockArray blockArray = decoder.DecodedBlocks[this.componentIndex]; |
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for (int i = 0; i < blockArray.Count; i++) |
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{ |
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this.ProcessBlockColors(decoder, ref blockArray.Buffer[i]); |
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} |
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} |
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/// <summary>
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/// Dequantize, perform the inverse DCT and store decodedBlock.Block to the into the corresponding <see cref="JpegPixelArea"/> instance.
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/// </summary>
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/// <param name="decoder">The <see cref="JpegDecoderCore"/></param>
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/// <param name="decodedBlock">The <see cref="DecodedBlock"/></param>
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private void ProcessBlockColors(JpegDecoderCore decoder, ref DecodedBlock decodedBlock) |
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{ |
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this.data.Block = decodedBlock.Block; |
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int qtIndex = decoder.ComponentArray[this.componentIndex].Selector; |
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this.data.QuantiazationTable = decoder.QuantizationTables[qtIndex]; |
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Block8x8F* b = this.pointers.Block; |
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Block8x8F.UnZig(b, this.pointers.QuantiazationTable, this.pointers.Unzig); |
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DCT.TransformIDCT(ref *b, ref *this.pointers.Temp1, ref *this.pointers.Temp2); |
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var destChannel = decoder.GetDestinationChannel(this.componentIndex); |
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var destArea = destChannel.GetOffsetedSubAreaForBlock(decodedBlock.Bx, decodedBlock.By); |
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destArea.LoadColorsFrom(this.pointers.Temp1, this.pointers.Temp2); |
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} |
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/// <summary>
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/// Holds the "large" data blocks needed for computations.
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/// </summary>
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[StructLayout(LayoutKind.Sequential)] |
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public struct ComputationData |
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{ |
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/// <summary>
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/// Temporal block 1 to store intermediate and/or final computation results
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/// </summary>
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public Block8x8F Block; |
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/// <summary>
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/// Temporal block 1 to store intermediate and/or final computation results
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/// </summary>
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public Block8x8F Temp1; |
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/// <summary>
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/// Temporal block 2 to store intermediate and/or final computation results
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/// </summary>
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public Block8x8F Temp2; |
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/// <summary>
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/// The quantization table as <see cref="Block8x8F"/>
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/// </summary>
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public Block8x8F QuantiazationTable; |
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/// <summary>
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/// The jpeg unzig data
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/// </summary>
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public UnzigData Unzig; |
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/// <summary>
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/// Creates and initializes a new <see cref="ComputationData"/> instance
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/// </summary>
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/// <returns>The <see cref="ComputationData"/></returns>
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public static ComputationData Create() |
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{ |
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ComputationData data = default(ComputationData); |
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data.Unzig = UnzigData.Create(); |
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return data; |
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} |
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} |
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/// <summary>
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/// Contains pointers to the memory regions of <see cref="ComputationData"/> so they can be easily passed around to pointer based utility methods of <see cref="Block8x8F"/>
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/// </summary>
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public struct DataPointers |
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{ |
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/// <summary>
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/// Pointer to <see cref="DecodedBlock.Block"/>
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/// </summary>
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public Block8x8F* Block; |
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/// <summary>
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/// Pointer to <see cref="ComputationData.Temp1"/>
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/// </summary>
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public Block8x8F* Temp1; |
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/// <summary>
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/// Pointer to <see cref="ComputationData.Temp2"/>
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/// </summary>
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public Block8x8F* Temp2; |
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/// <summary>
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/// Pointer to <see cref="ComputationData.QuantiazationTable"/>
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/// </summary>
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public Block8x8F* QuantiazationTable; |
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/// <summary>
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/// Pointer to <see cref="ComputationData.Unzig"/> as int*
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/// </summary>
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public int* Unzig; |
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/// <summary>
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/// Initializes a new instance of the <see cref="DataPointers" /> struct.
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/// </summary>
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/// <param name="dataPtr">Pointer to <see cref="ComputationData"/></param>
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internal DataPointers(ComputationData* dataPtr) |
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{ |
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this.Block = &dataPtr->Block; |
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this.Temp1 = &dataPtr->Temp1; |
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this.Temp2 = &dataPtr->Temp2; |
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this.QuantiazationTable = &dataPtr->QuantiazationTable; |
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this.Unzig = dataPtr->Unzig.Data; |
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} |
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} |
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} |
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} |
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