WPF BitmapSource /BitmapImage 获取像素点颜色

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Drawing;
using System.Windows.Forms;
using System.Windows.Forms.ComponentModel;

using System.Drawing.Imaging;
using System.Windows.Media.Imaging;
using System.Runtime.InteropServices;
using System.Windows.Media;
using System.Windows;

namespace WpfMosaic
{
    [StructLayout(LayoutKind.Sequential)]
    public struct PixelColor
    {
        public byte Blue;
        public byte Green;
        public byte Red;
        public byte Alpha;
    }

    public class Utils
    {
        public static PixelColor[,] GetPixels(BitmapSource source)
        {
            if (source.Format != PixelFormats.Bgra32)
                source = new FormatConvertedBitmap(source, PixelFormats.Bgra32, null, 0);
            PixelColor[,] pixels = new PixelColor[source.PixelWidth, source.PixelHeight];
            int stride = source.PixelWidth * ((source.Format.BitsPerPixel + 7) / 8);
            GCHandle pinnedPixels = GCHandle.Alloc(pixels, GCHandleType.Pinned);
            source.CopyPixels(
              new Int32Rect(0, 0, source.PixelWidth, source.PixelHeight),
              pinnedPixels.AddrOfPinnedObject(),
              pixels.GetLength(0) * pixels.GetLength(1) * 4,
                  stride);
            pinnedPixels.Free();
            return pixels;
        }
}
}

设置颜色后保存图片：

        public static Bitmap setColor(PixelColor[,] pixel) {

             Bitmap bmp = new Bitmap(1080,1920);

            // the target colors
            // var palette = new BitmapPalette(new List { Colors.Yellow, Colors.Red });
            int k = 0;
            for (int i = 0;i< 1080; i++)
            {
                for (int j = 0; j < bmp.Height; j++)
                {
                     bmp.SetPixel(i, j, System.Drawing.Color.FromArgb(pixel[i,j].Alpha, pixel[i, j].Red, pixel[i, j].Green, pixel[i, j].Blue));
                    
                    k++;
                }
            }
           

            bmp.Save(@"C:\Users\gwang\Pictures\0011122.jpg", ImageFormat.Jpeg);
           
            return bmp;


        }

// 用法：
//var pixels = GetPixels(image);
//if(pixels[7, 3].Red > 4)

上面发现颜色不对。。。。。。。。。。。。。

下面的发现 颜色变黄了：

  public static PixelColor[,] GetPixels2(BitmapSource source)
        {
            PixelColor[,] result= new PixelColor[source.PixelWidth, source.PixelHeight];

            int stride = source.PixelWidth * 4;
            int size = source.PixelHeight * stride;
            byte[] pixels = new byte[size];
            source.CopyPixels(pixels, stride, 0);

            for (int y = 0; y < source.PixelHeight; y++)
            {
                for (int x = 0; x < source.PixelWidth; x++)
                {
                  
                    int index = y * stride + 4 * x;
                    byte red = pixels[index];
                    byte green = pixels[index + 1];
                    byte blue = pixels[index + 2];
                    byte alpha = pixels[index + 3];
                    result[x, y] = new PixelColor()
                    {
                        Alpha = alpha,
                        Red = red,
                        Green = green,
                        Blue = blue
                    };

                }

            }

            return result;



        }

蛋疼。。。。。。。。。。。。。。。。。。。。