以Lockbits的方式访问bitmap

转载自：http://www.cnblogs.com/xiashengwang/p/4225848.html

2015-01-15 11:38 by xiashengwang, 585 阅读, 0 评论, 收藏, 编辑

用Bitmap.GetPixel和Bitmap.SetPixel访问像素点实在是太慢了，必须要用LockBits的方式访问内存才能改善，这里贴一个快速访问Bitmap每个像素点的包装类，是国外一个老外写的，感觉很好用。

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public class LockBitmap {     Bitmap source = null;     IntPtr Iptr = IntPtr.Zero;     BitmapData bitmapData = null;       public byte[] Pixels { get; set; }     public int Depth { get; private set; }     public int Width { get; private set; }     public int Height { get; private set; }       public LockBitmap(Bitmap source)     {         this.source = source;     }       /// <summary>     /// Lock bitmap data     /// </summary>     public void LockBits()     {         try         {             // Get width and height of bitmap             Width = source.Width;             Height = source.Height;               // get total locked pixels count             int PixelCount = Width * Height;               // Create rectangle to lock             System.Drawing.Rectangle rect = new System.Drawing.Rectangle(0, 0, Width, Height);               // get source bitmap pixel format size             Depth = System.Drawing.Bitmap.GetPixelFormatSize(source.PixelFormat);               // Check if bpp (Bits Per Pixel) is 8, 24, or 32             if (Depth != 8 && Depth != 24 && Depth != 32)             {                 throw new ArgumentException("Only 8, 24 and 32 bpp images are supported.");             }               // Lock bitmap and return bitmap data             bitmapData = source.LockBits(rect, ImageLockMode.ReadWrite,                                          source.PixelFormat);               // create byte array to copy pixel values             int step = Depth / 8;             Pixels = new byte[PixelCount * step];             Iptr = bitmapData.Scan0;               // Copy data from pointer to array             Marshal.Copy(Iptr, Pixels, 0, Pixels.Length);         }         catch (Exception ex)         {             throw ex;         }     }       /// <summary>     /// Unlock bitmap data     /// </summary>     public void UnlockBits()     {         try         {             // Copy data from byte array to pointer             Marshal.Copy(Pixels, 0, Iptr, Pixels.Length);               // Unlock bitmap data             source.UnlockBits(bitmapData);         }         catch (Exception ex)         {             throw ex;         }     }       /// <summary>     /// Get the color of the specified pixel     /// </summary>     /// <param name="x"></param>     /// <param name="y"></param>     /// <returns></returns>     public Color GetPixel(int x, int y)     {         Color clr = Color.Empty;           // Get color components count         int cCount = Depth / 8;           // Get start index of the specified pixel         int i = ((y * Width) + x) * cCount;           if (i > Pixels.Length - cCount)             throw new IndexOutOfRangeException();           if (Depth == 32) // For 32 bpp get Red, Green, Blue and Alpha         {             byte b = Pixels[i];             byte g = Pixels[i + 1];             byte r = Pixels[i + 2];             byte a = Pixels[i + 3]; // a             clr = Color.FromArgb(a, r, g, b);         }         if (Depth == 24) // For 24 bpp get Red, Green and Blue         {             byte b = Pixels[i];             byte g = Pixels[i + 1];             byte r = Pixels[i + 2];             clr = Color.FromArgb(r, g, b);         }         if (Depth == 8)         // For 8 bpp get color value (Red, Green and Blue values are the same)         {             byte c = Pixels[i];             clr = Color.FromArgb(c, c, c);         }         return clr;     }       /// <summary>     /// Set the color of the specified pixel     /// </summary>     /// <param name="x"></param>     /// <param name="y"></param>     /// <param name="color"></param>     public void SetPixel(int x, int y, Color color)     {         // Get color components count         int cCount = Depth / 8;           // Get start index of the specified pixel         int i = ((y * Width) + x) * cCount;           if (Depth == 32) // For 32 bpp set Red, Green, Blue and Alpha         {             Pixels[i] = color.B;             Pixels[i + 1] = color.G;             Pixels[i + 2] = color.R;             Pixels[i + 3] = color.A;         }         if (Depth == 24) // For 24 bpp set Red, Green and Blue         {             Pixels[i] = color.B;             Pixels[i + 1] = color.G;             Pixels[i + 2] = color.R;         }         if (Depth == 8)         // For 8 bpp set color value (Red, Green and Blue values are the same)         {             Pixels[i] = color.B;         }     }       public bool IsValidCoordinate(int x, int y)     {         return x >= 0 && x < this.Width && y > 0 && y < this.Height;     } }

还有一个时间测算的类，可以计算代码的时间差，跟Stopwatch差不多

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public class Benchmark {     private static DateTime startDate = DateTime.MinValue;     private static DateTime endDate = DateTime.MinValue;       public static TimeSpan Span { get { return endDate.Subtract(startDate); } }       public static void Start() { startDate = DateTime.Now; }       public static void End() { endDate = DateTime.Now; }       public static double GetSeconds()     {         if (endDate == DateTime.MinValue) return 0.0;         else return Span.TotalSeconds;     } }