mirror of https://github.com/SixLabors/ImageSharp
James Jackson-South
8 years ago
22 changed files with 348 additions and 511 deletions
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// Copyright (c) Six Labors and contributors.
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// Licensed under the Apache License, Version 2.0.
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using System; |
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using System.Runtime.CompilerServices; |
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using SixLabors.ImageSharp.PixelFormats; |
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using SixLabors.Primitives; |
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namespace SixLabors.ImageSharp.Processing.Processors |
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{ |
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/// <summary>
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/// Provides methods that allow the resizing of images using various algorithms.
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/// Adapted from <see href="http://www.realtimerendering.com/resources/GraphicsGems/gemsiii/filter_rcg.c"/>
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/// </summary>
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/// <typeparam name="TPixel">The pixel format.</typeparam>
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internal abstract class ResamplingWeightedProcessor<TPixel> : TransformProcessorBase<TPixel> |
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where TPixel : struct, IPixel<TPixel> |
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{ |
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/// <summary>
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/// Initializes a new instance of the <see cref="ResamplingWeightedProcessor{TPixel}"/> class.
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/// </summary>
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/// <param name="sampler">The sampler to perform the resize operation.</param>
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/// <param name="width">The target width.</param>
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/// <param name="height">The target height.</param>
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/// <param name="resizeRectangle">
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/// The <see cref="Rectangle"/> structure that specifies the portion of the target image object to draw to.
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/// </param>
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protected ResamplingWeightedProcessor(IResampler sampler, int width, int height, Rectangle resizeRectangle) |
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{ |
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Guard.NotNull(sampler, nameof(sampler)); |
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Guard.MustBeGreaterThan(width, 0, nameof(width)); |
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Guard.MustBeGreaterThan(height, 0, nameof(height)); |
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this.Sampler = sampler; |
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this.Width = width; |
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this.Height = height; |
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this.ResizeRectangle = resizeRectangle; |
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} |
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/// <summary>
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/// Gets the sampler to perform the resize operation.
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/// </summary>
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public IResampler Sampler { get; } |
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/// <summary>
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/// Gets or sets the width.
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/// </summary>
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public int Width { get; protected set; } |
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/// <summary>
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/// Gets or sets the height.
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/// </summary>
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public int Height { get; protected set; } |
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/// <summary>
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/// Gets or sets the resize rectangle.
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/// </summary>
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public Rectangle ResizeRectangle { get; protected set; } |
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/// <summary>
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/// Gets or sets the horizontal weights.
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/// </summary>
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protected WeightsBuffer HorizontalWeights { get; set; } |
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/// <summary>
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/// Gets or sets the vertical weights.
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/// </summary>
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protected WeightsBuffer VerticalWeights { get; set; } |
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/// <summary>
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/// Computes the weights to apply at each pixel when resizing.
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/// </summary>
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/// <param name="destinationSize">The destination size</param>
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/// <param name="sourceSize">The source size</param>
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/// <returns>The <see cref="WeightsBuffer"/></returns>
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// TODO: Made internal to simplify experimenting with weights data. Make it protected again when finished figuring out how to optimize all the stuff!
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internal unsafe WeightsBuffer PrecomputeWeights(int destinationSize, int sourceSize) |
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{ |
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float ratio = (float)sourceSize / destinationSize; |
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float scale = ratio; |
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if (scale < 1F) |
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{ |
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scale = 1F; |
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} |
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IResampler sampler = this.Sampler; |
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float radius = MathF.Ceiling(scale * sampler.Radius); |
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var result = new WeightsBuffer(sourceSize, destinationSize); |
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for (int i = 0; i < destinationSize; i++) |
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{ |
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float center = ((i + .5F) * ratio) - .5F; |
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// Keep inside bounds.
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int left = (int)Math.Ceiling(center - radius); |
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if (left < 0) |
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{ |
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left = 0; |
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} |
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int right = (int)Math.Floor(center + radius); |
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if (right > sourceSize - 1) |
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{ |
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right = sourceSize - 1; |
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} |
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float sum = 0; |
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WeightsWindow ws = result.GetWeightsWindow(i, left, right); |
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result.Weights[i] = ws; |
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ref float weightsBaseRef = ref ws.GetStartReference(); |
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for (int j = left; j <= right; j++) |
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{ |
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float weight = sampler.GetValue((j - center) / scale); |
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sum += weight; |
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// weights[j - left] = weight:
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Unsafe.Add(ref weightsBaseRef, j - left) = weight; |
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} |
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// Normalise, best to do it here rather than in the pixel loop later on.
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if (sum > 0) |
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{ |
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for (int w = 0; w < ws.Length; w++) |
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{ |
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// weights[w] = weights[w] / sum:
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ref float wRef = ref Unsafe.Add(ref weightsBaseRef, w); |
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wRef = wRef / sum; |
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} |
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} |
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} |
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return result; |
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} |
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/// <inheritdoc/>
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protected override void BeforeApply(ImageFrame<TPixel> source, ImageFrame<TPixel> destination, Rectangle sourceRectangle, Configuration configuration) |
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{ |
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if (!(this.Sampler is NearestNeighborResampler)) |
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{ |
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this.HorizontalWeights = this.PrecomputeWeights( |
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this.ResizeRectangle.Width, |
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sourceRectangle.Width); |
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this.VerticalWeights = this.PrecomputeWeights( |
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this.ResizeRectangle.Height, |
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sourceRectangle.Height); |
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} |
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} |
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/// <inheritdoc />
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protected override void AfterApply(ImageFrame<TPixel> source, ImageFrame<TPixel> destination, Rectangle sourceRectangle, Configuration configuration) |
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{ |
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base.AfterApply(source, destination, sourceRectangle, configuration); |
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this.HorizontalWeights?.Dispose(); |
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this.HorizontalWeights = null; |
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this.VerticalWeights?.Dispose(); |
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this.VerticalWeights = null; |
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} |
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} |
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} |
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