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JimBobSquarePantsJimBobSquarePants
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Merge pull request #1561 from rold2007/ImageIntegral
Added image integral algorithm.
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‎src/ImageSharp/Processing/Extensions/ProcessingExtensions.IntegralImage.cs‎

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// Copyright (c) Six Labors.
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// Licensed under the Apache License, Version 2.0.
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using System;
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using System.Buffers;
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using SixLabors.ImageSharp.Advanced;
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using SixLabors.ImageSharp.Memory;
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using SixLabors.ImageSharp.PixelFormats;
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namespace SixLabors.ImageSharp.Processing
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{
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/// <summary>
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/// Defines extensions that allow the computation of image integrals on an <see cref="Image"/>
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/// </summary>
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public static partial class ProcessingExtensions
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{
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/// <summary>
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/// Apply an image integral. <See href="https://en.wikipedia.org/wiki/Summed-area_table"/>
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/// </summary>
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/// <param name="source">The image on which to apply the integral.</param>
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/// <typeparam name="TPixel">The type of the pixel.</typeparam>
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/// <returns>The <see cref="Buffer2D{T}"/> containing all the sums.</returns>
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public static Buffer2D<ulong> CalculateIntegralImage<TPixel>(this Image<TPixel> source)
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where TPixel : unmanaged, IPixel<TPixel>
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{
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Configuration configuration = source.GetConfiguration();
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int endY = source.Height;
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int endX = source.Width;
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Buffer2D<ulong> intImage = configuration.MemoryAllocator.Allocate2D<ulong>(source.Width, source.Height);
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ulong sumX0 = 0;
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using (IMemoryOwner<L8> tempRow = configuration.MemoryAllocator.Allocate<L8>(source.Width))
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{
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Span<L8> tempSpan = tempRow.GetSpan();
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Span<TPixel> sourceRow = source.GetPixelRowSpan(0);
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Span<ulong> destRow = intImage.GetRowSpan(0);
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PixelOperations<TPixel>.Instance.ToL8(configuration, sourceRow, tempSpan);
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// First row
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for (int x = 0; x < endX; x++)
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{
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sumX0 += tempSpan[x].PackedValue;
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destRow[x] = sumX0;
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}
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Span<ulong> previousDestRow = destRow;
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// All other rows
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for (int y = 1; y < endY; y++)
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{
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sourceRow = source.GetPixelRowSpan(y);
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destRow = intImage.GetRowSpan(y);
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PixelOperations<TPixel>.Instance.ToL8(configuration, sourceRow, tempSpan);
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// Process first column
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sumX0 = tempSpan[0].PackedValue;
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destRow[0] = sumX0 + previousDestRow[0];
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// Process all other colmns
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for (int x = 1; x < endX; x++)
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{
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sumX0 += tempSpan[x].PackedValue;
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destRow[x] = sumX0 + previousDestRow[x];
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}
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previousDestRow = destRow;
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}
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}
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return intImage;
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}
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}
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}

‎src/ImageSharp/Processing/Extensions/ProcessingExtensions.cs‎

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/// <summary>
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/// Adds extensions that allow the processing of images to the <see cref="Image{TPixel}"/> type.
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/// </summary>
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public static class ProcessingExtensions
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public static partial class ProcessingExtensions
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{
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/// <summary>
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/// Mutates the source image by applying the image operation to it.

‎tests/ImageSharp.Tests/Processing/IntegralImageTests.cs‎

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// Copyright (c) Six Labors.
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// Licensed under the Apache License, Version 2.0.
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using SixLabors.ImageSharp.Memory;
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using SixLabors.ImageSharp.PixelFormats;
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using SixLabors.ImageSharp.Processing;
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using Xunit;
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namespace SixLabors.ImageSharp.Tests.Processing.Transforms
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{
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public class IntegralImageTests : BaseImageOperationsExtensionTest
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{
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[Theory]
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[WithFile(TestImages.Png.Bradley01, PixelTypes.Rgba32)]
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[WithFile(TestImages.Png.Bradley02, PixelTypes.Rgba32)]
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[WithFile(TestImages.Png.Ducky, PixelTypes.Rgba32)]
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public void CalculateIntegralImage_Rgba32Works(TestImageProvider<Rgba32> provider)
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{
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using Image<Rgba32> image = provider.GetImage();
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// Act:
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Buffer2D<ulong> integralBuffer = image.CalculateIntegralImage();
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// Assert:
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VerifySumValues(provider, integralBuffer, (Rgba32 pixel) =>
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{
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L8 outputPixel = default;
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outputPixel.FromRgba32(pixel);
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return outputPixel.PackedValue;
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});
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}
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[Theory]
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[WithFile(TestImages.Png.Bradley01, PixelTypes.L8)]
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[WithFile(TestImages.Png.Bradley02, PixelTypes.L8)]
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public void CalculateIntegralImage_L8Works(TestImageProvider<L8> provider)
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{
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using Image<L8> image = provider.GetImage();
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// Act:
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Buffer2D<ulong> integralBuffer = image.CalculateIntegralImage();
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// Assert:
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VerifySumValues(provider, integralBuffer, (L8 pixel) => { return pixel.PackedValue; });
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}
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private static void VerifySumValues<TPixel>(
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TestImageProvider<TPixel> provider,
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Buffer2D<ulong> integralBuffer,
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System.Func<TPixel, ulong> getPixel)
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where TPixel : unmanaged, IPixel<TPixel>
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{
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Image<TPixel> image = provider.GetImage();
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// Check top-left corner
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Assert.Equal(getPixel(image[0, 0]), integralBuffer[0, 0]);
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ulong pixelValues = 0;
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pixelValues += getPixel(image[0, 0]);
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pixelValues += getPixel(image[1, 0]);
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pixelValues += getPixel(image[0, 1]);
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pixelValues += getPixel(image[1, 1]);
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// Check top-left 2x2 pixels
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Assert.Equal(pixelValues, integralBuffer[1, 1]);
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pixelValues = 0;
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pixelValues += getPixel(image[image.Width - 3, 0]);
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pixelValues += getPixel(image[image.Width - 2, 0]);
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pixelValues += getPixel(image[image.Width - 1, 0]);
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pixelValues += getPixel(image[image.Width - 3, 1]);
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pixelValues += getPixel(image[image.Width - 2, 1]);
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pixelValues += getPixel(image[image.Width - 1, 1]);
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// Check top-right 3x2 pixels
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Assert.Equal(pixelValues, integralBuffer[image.Width - 1, 1] + 0 - 0 - integralBuffer[image.Width - 4, 1]);
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pixelValues = 0;
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pixelValues += getPixel(image[0, image.Height - 3]);
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pixelValues += getPixel(image[0, image.Height - 2]);
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pixelValues += getPixel(image[0, image.Height - 1]);
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pixelValues += getPixel(image[1, image.Height - 3]);
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pixelValues += getPixel(image[1, image.Height - 2]);
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pixelValues += getPixel(image[1, image.Height - 1]);
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// Check bottom-left 2x3 pixels
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Assert.Equal(pixelValues, integralBuffer[1, image.Height - 1] + 0 - integralBuffer[1, image.Height - 4] - 0);
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pixelValues = 0;
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pixelValues += getPixel(image[image.Width - 3, image.Height - 3]);
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pixelValues += getPixel(image[image.Width - 2, image.Height - 3]);
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pixelValues += getPixel(image[image.Width - 1, image.Height - 3]);
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pixelValues += getPixel(image[image.Width - 3, image.Height - 2]);
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pixelValues += getPixel(image[image.Width - 2, image.Height - 2]);
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pixelValues += getPixel(image[image.Width - 1, image.Height - 2]);
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pixelValues += getPixel(image[image.Width - 3, image.Height - 1]);
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pixelValues += getPixel(image[image.Width - 2, image.Height - 1]);
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pixelValues += getPixel(image[image.Width - 1, image.Height - 1]);
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// Check bottom-right 3x3 pixels
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Assert.Equal(pixelValues, integralBuffer[image.Width - 1, image.Height - 1] + integralBuffer[image.Width - 4, image.Height - 4] - integralBuffer[image.Width - 1, image.Height - 4] - integralBuffer[image.Width - 4, image.Height - 1]);
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}
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}
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}

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