从图像创建1bpp遮罩 [英] Create 1bpp mask from image

问题描述

如何在C＃中使用GDI的图像创建每像素1位掩码？我试图创建掩码的图像保存在System.Drawing.Graphics对象中。

我已经在循环中看到了使用Get / SetPixel的示例，它太慢了。我感兴趣的方法是仅使用BitBlits的方法，如 this 一>。我只是无法在C＃中使用它，任何帮助都非常感谢。

解决方案

试试这个：

  using System.Drawing; 
使用System.Drawing.Imaging; 
使用System.Runtime.InteropServices; 
  

...

  public static Bitmap BitmapTo1Bpp（Bitmap img）{
 int w = img.Width; 
 int h = img.Height; 
位图bmp =新位图（w，h，PixelFormat.Format1bppIndexed）; 
 BitmapData data = bmp.LockBits（new Rectangle（0，0，w，h），ImageLockMode.ReadWrite，PixelFormat.Format1bppIndexed）; 
 for（int y = 0; y  byte [] scan = new byte [（w + 7）/ 8]; 
 for（int x = 0; x  Color c = img.GetPixel（x，y）; （c.GetBrightness（）> = 0.5）scan [x / 8] | =（byte）（0x80>>（x％8））; 
 
 Marshal.Copy（scan，0，（IntPtr）（（int）data.Scan0 + data.Stride * y），scan.Length）; 
} 
 bmp.UnlockBits（data）; 
 return bmp; 
} 
  

GetPixel（）速度很慢，可以用不安全的字节加速* 。

How do you create a 1 bit per pixel mask from an image using GDI in C#? The image I am trying to create the mask from is held in a System.Drawing.Graphics object.

I have seen examples that use Get/SetPixel in a loop, which are too slow. The method that interests me is one that uses only BitBlits, like this. I just can't get it to work in C#, any help is much appreciated.

解决方案

Try this:

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

...

   public static Bitmap BitmapTo1Bpp(Bitmap img) {
      int w = img.Width;
      int h = img.Height;
      Bitmap bmp = new Bitmap(w, h, PixelFormat.Format1bppIndexed);
      BitmapData data = bmp.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadWrite, PixelFormat.Format1bppIndexed);
      for (int y = 0; y < h; y++) {
        byte[] scan = new byte[(w + 7) / 8];
        for (int x = 0; x < w; x++) {
          Color c = img.GetPixel(x, y);
          if (c.GetBrightness() >= 0.5) scan[x / 8] |= (byte)(0x80 >> (x % 8));
        }
        Marshal.Copy(scan, 0, (IntPtr)((int)data.Scan0 + data.Stride * y), scan.Length);
      }
      bmp.UnlockBits(data);
      return bmp;
    }

GetPixel() is slow, you can speed it up with an unsafe byte*.

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