改进图像合成算法c＃.NET-Java 学习之路

我想知道是否有人可以说明我可以做的改进，使这个合成算法更快 . 做什么是将3个图像分割成第一个图像红色通道，第二个图像绿色通道和第三个图像蓝色通道，并将它们合成为一个新图像 . 现在它起作用但速度极慢 . 我想到它必须对所有图像组件进行逐像素处理的原因 .

过程是：

对于所有图像：提取相应的R G和B值 - >合成为1个图像 - >保存新图像 .

foreach (Image[] QRE2ImgComp in QRE2IMGArray)
{
    Globals.updProgress = "Processing frames: " + k + " of " + QRE2IMGArray.Count + " frames done.";
    QRMProgressUpd(EventArgs.Empty);

    Image RedLayer = GetRedImage(QRE2ImgComp[0]);
    QRE2ImgComp[0] = RedLayer;

    Image GreenLayer = GetGreenImage(QRE2ImgComp[1]);
    QRE2ImgComp[1] = GreenLayer;

    Image BlueLayer = GetBlueImage(QRE2ImgComp[2]);
    QRE2ImgComp[2] = BlueLayer;


    Bitmap composite = new Bitmap(QRE2ImgComp[0].Height, QRE2ImgComp[0].Width);

    Color Rlayer,Glayer,Blayer;
    byte R, G, B;

    for (int y = 0; y < composite.Height; y++)
    {
        for (int x = 0; x < composite.Width; x++)
        {
            //pixelColorAlpha = composite.GetPixel(x, y);

            Bitmap Rcomp = new Bitmap(QRE2ImgComp[0]);
            Bitmap Gcomp = new Bitmap(QRE2ImgComp[1]);
            Bitmap Bcomp = new Bitmap(QRE2ImgComp[2]);

            Rlayer = Rcomp.GetPixel(x, y);
            Glayer = Gcomp.GetPixel(x, y);
            Blayer = Bcomp.GetPixel(x, y);

            R = (byte)(Rlayer.R);
            G = (byte)(Glayer.G);
            B = (byte)(Blayer.B);
            composite.SetPixel(x, y, Color.FromArgb((int)R, (int)G, (int)B));
        }
    }


    Globals.updProgress = "Saving frame...";
    QRMProgressUpd(EventArgs.Empty);
    Image tosave = composite;
    Globals.QRFrame = tosave;
    tosave.Save("C:\\QRItest\\E" + k + ".png", ImageFormat.Png);
    k++;

}

这里参考红色通道滤波器方法对蓝色和绿色相对相同：

public Image GetRedImage(Image sourceImage)
{
    Bitmap bmp = new Bitmap(sourceImage);
    Bitmap redBmp = new Bitmap(sourceImage.Width, sourceImage.Height);

        for (int x = 0; x < bmp.Width; x++)
        {
            for (int y = 0; y < bmp.Height; y++)
            {
                Color pxl = bmp.GetPixel(x, y);
                Color redPxl = Color.FromArgb((int)pxl.R, 0, 0);

                redBmp.SetPixel(x, y, redPxl);
            }
        }
        Image tout = (Image)redBmp;

        return tout;
}

2 回答

我完全同意Yahia在提高绩效的答案中列出的观点 . 我想再补充一点关于性能的观点 . 您可以使用.Net Framework的 Parallel 类来并行执行for循环 . 以下示例使用 LockBits 方法和 Parallel 类来提高性能（假设每像素32位（PixelFormat.Format32bppArgb））：

public unsafe static Bitmap GetBlueImagePerf(Image sourceImage)
{
  int width = sourceImage.Width;
  int height = sourceImage.Height;

  Bitmap bmp = new Bitmap(sourceImage);
  Bitmap redBmp = new Bitmap(width, height, bmp.PixelFormat);

  BitmapData bd = bmp.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.ReadOnly, PixelFormat.Format32bppRgb);
  BitmapData bd2 = redBmp.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.WriteOnly, PixelFormat.Format32bppRgb);
  byte* source = (byte*)bd.Scan0.ToPointer();
  byte* target = (byte*)bd2.Scan0.ToPointer();

  int stride = bd.Stride;

  Parallel.For(0, height, (y1) =>
  {
    byte* s = source + (y1 * stride);
    byte* t = target + (y1 * stride);
    for (int x = 0; x < width; x++)
    {
      // use t[1], s[1] to access green channel
      // use t[2], s[2] to access red channel
      t[0] = s[0]; 
      t += 4;       // Add bytes per pixel to current position.
      s += 4;       // For other pixel formats this value is different.
    }
  });

  bmp.UnlockBits(bd);
  redBmp.UnlockBits(bd2);


  return redBmp;
}

public unsafe static void DoImageConversion()
{
  Bitmap RedLayer   = GetRedImagePerf(Image.FromFile("image_path1"));
  Bitmap GreenLayer = GetGreenImagePerf(Image.FromFile("image_path2"));
  Bitmap BlueLayer  = GetBlueImagePerf(Image.FromFile("image_path3"));

  Bitmap composite =
    new Bitmap(RedLayer.Width, RedLayer.Height, RedLayer.PixelFormat);      

  BitmapData bd = composite.LockBits(new Rectangle(0, 0, RedLayer.Width, RedLayer.Height), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);
  byte* comp = (byte*)bd.Scan0.ToPointer();

  BitmapData bdRed = RedLayer.LockBits(new Rectangle(0, 0, RedLayer.Width, RedLayer.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
  BitmapData bdGreen = GreenLayer.LockBits(new Rectangle(0, 0, RedLayer.Width, RedLayer.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
  BitmapData bdBlue = BlueLayer.LockBits(new Rectangle(0, 0, RedLayer.Width, RedLayer.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);

  byte* red = (byte*)bdRed.Scan0.ToPointer();
  byte* green = (byte*)bdGreen.Scan0.ToPointer();
  byte* blue = (byte*)bdBlue.Scan0.ToPointer();

  int stride = bdRed.Stride;

  Parallel.For(0, bdRed.Height, (y1) =>
  {
    byte* r = red + (y1 * stride);
    byte* g = green + (y1 * stride);
    byte* b = blue + (y1 * stride);
    byte* c = comp + (y1 * stride);

    for (int x = 0; x < bdRed.Width; x++)
    {
      c[0] = b[0];
      c[1] = g[1];
      c[2] = r[2];

      r += 4; // Add bytes per pixel to current position.
      g += 4; // For other pixel formats this value is different.
      b += 4; // Use Image.GetPixelFormatSize to get number of bits per pixel
      c += 4;
    }
  });

  composite.Save("save_image_path", ImageFormat.Jpeg);
}

希望，这个答案为您提供了改进代码的起点 .

回复于 2024-05-19T15:16:32+08:00

1
Move these
```
Bitmap Rcomp = new Bitmap(QRE2ImgComp[0]);
    Bitmap Gcomp = new Bitmap(QRE2ImgComp[1]);
    Bitmap Bcomp = new Bitmap(QRE2ImgComp[2]);
```
outside the for-loops!

其他非常重要的一点：
- avoid using GetPixel - it is VERY SLOW!
- Checkout LockBits等 - 这就是通常在.NET中进行像素级访问的方式
- 考虑使用第三方库（免费或商业）......有几个内置了一些优化方法来做你想要实现的...
回复于 2024-05-19T15:16:32+08:00

改进图像合成算法c＃.NET

2 回答

相关问题