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书到用时方恨少，钱到月底不够花。我们上github搜索关键字，限定语言，你会发现没有C#这个选项... 不行，别人有的我们也要有！

资源有限，人脉有限。有幸得高人指点，充分利用C#语言的多维数组，让排列正确实现的同时又保证了代码的优雅性和可读性。

欢迎白嫖🍦！

参考文献和代码

• ImageSharp

• RGB多种格式简要介绍

• 图像数据通道格式：NCHW和NHWC的区别
  

  重点

代码

• using

using SixLabors.ImageSharp;
using SixLabors.ImageSharp.PixelFormats;
using System.Runtime.InteropServices;

• 图像转NHWC -- 三维矩阵

public static ReadOnlySpan<byte> ImageToNHWC(Image<Rgb24> image)
{
    var hwc = new byte[image.Height, image.Width, 3];

    for (int h = 0; h < image.Height; h++)
    {
        for (int w = 0; w < image.Width; w++)
        {
            var px = image[w, h];

            hwc[h, w, 0] = px.R;
            hwc[h, w, 1] = px.G;
            hwc[h, w, 2] = px.B;
        }
    }

    return MemoryMarshal.CreateReadOnlySpan(ref hwc[0, 0, 0], 3 * image.Height * image.Width);
}

• 图像转NCHW -- 三维矩阵

public static ReadOnlySpan<byte> ImageToNCHW(Image<Rgb24> image)
{
    var chw = new byte[3, image.Height, image.Width];

    for (int w = 0; w < image.Width; w++)
    {
        for (int h = 0; h < image.Height; h++)
        {
            var px = image[w, h];

            chw[0, h, w] = px.R;
            chw[1, h, w] = px.G;
            chw[2, h, w] = px.B;
        }
    }

    return MemoryMarshal.CreateReadOnlySpan(ref chw[0, 0, 0], 3 * image.Height * image.Width);
}

• NHWC转NCHW -- 三维矩阵

public static ReadOnlySpan<byte> NHWCToNCHW(ReadOnlySpan<byte> bytes, int width, int height)
{
    var chw = new byte[3, height, width];

    for (int c = 0; c < 3; c++)
    {
        for (int h = 0; h < height; h++)
        {
            for (int w = 0; w < width; w++)
            {
                chw[c, h, w] = bytes[(h * width + w) * 3 + c];
            }
        }
    }

    return MemoryMarshal.CreateReadOnlySpan(ref chw[0, 0, 0], 3 * height * width);
}

• NCHW转NHWC -- 三维矩阵

public static ReadOnlySpan<byte> NCHWToNHWC(ReadOnlySpan<byte> bytes, int width, int height)
{
    var hwc = new byte[height, width, 3];

    for (int c = 0; c < 3; c++)
    {
        for (int h = 0; h < height; h++)
        {
            for (int w = 0; w < width; w++)
            {
                hwc[h, w, c] = bytes[(c * height + h) * width + w];
            }
        }
    }

    return MemoryMarshal.CreateReadOnlySpan(ref hwc[0, 0, 0], 3 * height * width);
}

• NCHW转图像 -- 数组切片

public static Image<Rgb24> NCHWToImage(ReadOnlySpan<byte> bytes, int width, int height)
{
    var length = width * height;

    var rChannel = bytes.Slice(0, length);
    var gChannel = bytes.Slice(1 * length, length);
    var bChannel = bytes.Slice(2 * length, length);

    var image = new Image<Rgb24>(width, height);

    for (int h = 0; h < height; h++)
    {
        for (int w = 0; w < width; w++)
        {
            var r = rChannel[h * width + w];
            var g = gChannel[h * width + w];
            var b = bChannel[h * width + w];

            image[w, h] = new Rgb24(r, g, b);
        }
    }

    return image ;
}

• NHWC转图像 -- 每三个字节一组，顺序填充到像素

public static Image<Rgb24> NHWCToImage(ReadOnlySpan<byte> bytes, int width, int height)
{
    var image = new Image<Rgb24>(width, height);

    for (int h = 0; h < height; h++)
    {
        for (int w = 0; w < width; w++)
        {
            var r = bytes[(h * width + w) * 3 + 0];
            var g = bytes[(h * width + w) * 3 + 1];
            var b = bytes[(h * width + w) * 3 + 2];

            image[w, h] = new Rgb24(r, g, b);
        }
    }

    return image;
}