C#访问BitMap几种方法效率比较

bmpGray = new Bitmap("validCode.bmp"); Stopwatch stopwatch = new Stopwatch(); stopwatch.Start(); for (int i = 0; i < bmpGray.Height; i++) { for (int j = 0; j < bmpGray.Width; j++) { Color color = bmpGray.GetPixel(j, i); int aver = (color.R + color.G + color.B) / 3; bmpGray.SetPixel(j, i, Color.FromArgb(aver, aver, aver)); } } stopwatch.Stop(); Stopwatch stopwatch2 = new Stopwatch(); stopwatch2.Start(); bmpGray = new Bitmap("validCode.bmp"); Rectangle rect = new Rectangle(1, 1, bmpGray.Width - 2, bmpGray.Height - 2); BitmapData bmpData = bmpGray.LockBits(rect, ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); IntPtr ptr = bmpData.Scan0; for (int i = 0; i < rect.Height; i++) { for (int j = 0; j < rect.Width; j++) { int aver = 0; for (int k = 0; k < 3; k++) { aver += Marshal.ReadByte(ptr, i * bmpData.Stride + j * 3 + k); } aver /= 3; for (int k = 0; k < 3; k++) { Marshal.WriteByte(ptr, i * bmpData.Stride + j * 3 + k, (byte)aver); } } } bmpGray.UnlockBits(bmpData); stopwatch2.Stop(); Stopwatch stopwatch3 = new Stopwatch(); stopwatch3.Start(); bmpGray = new Bitmap("validCode.bmp"); Rectangle rect2 = new Rectangle(1, 1, bmpGray.Width - 2, bmpGray.Height - 2); BitmapData bmpData2 = bmpGray.LockBits(rect2, ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); IntPtr ptr2 = bmpData2.Scan0; byte[] rgbValues = new byte[rect2.Height * rect2.Width * 3]; Marshal.Copy(ptr2, rgbValues, 0, rgbValues.Length); for (int i = 0; i < rgbValues.Length; i += 3) { int colorTemp = rgbValues[i] + rgbValues[i + 1] + rgbValues[i + 2]; colorTemp /= 3; rgbValues[i] = rgbValues[i + 1] = rgbValues[i + 2] = (byte)colorTemp; } Marshal.Copy(rgbValues, 0, ptr2, rgbValues.Length); bmpGray.UnlockBits(bmpData); stopwatch3.Stop(); Stopwatch stopwatch4 = new Stopwatch(); stopwatch4.Start(); bmpGray = new Bitmap("validCode.bmp"); Rectangle rect4 = new Rectangle(1, 1, bmpGray.Width - 2, bmpGray.Height - 2); BitmapData bmpData4 = bmpGray.LockBits(rect4, ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); unsafe { byte* ptr4 = (byte*)(bmpData4.Scan0); for (int i = 0; i < rect4.Height; i++) { for (int j = 0; j < rect4.Width; j++) { int aver = 0; for (int k = 0; k < 3; k++) { aver += ptr4[i * bmpData4.Stride + j * 3 + k]; } aver /= 3; for (int k = 0; k < 3; k++) { ptr4[i * bmpData4.Stride + j * 3 + k] = (byte)aver; } } } } bmpGray.UnlockBits(bmpData4); stopwatch4.Stop();

 

result：

stopwatch{System.Diagnostics.Stopwatch} elapsed: 0x0000000394eabae0 Elapsed: {00:00:04.8191978} ElapsedMilliseconds: 0x00000000000012d3 ElapsedTicks: 0x0000000394eabae0 IsRunning: false isRunning: false startTimeStamp: 0x000017d9416c6260stopwatch2{System.Diagnostics.Stopwatch} elapsed: 0x0000000049f480f0 Elapsed: {00:00:00.3886984} ElapsedMilliseconds: 0x0000000000000184 ElapsedTicks: 0x0000000049f480f0 IsRunning: false isRunning: false startTimeStamp: 0x000017dcd65729e0stopwatch3{System.Diagnostics.Stopwatch} elapsed: 0x000000000c25bb00 Elapsed: {00:00:00.0638450} ElapsedMilliseconds: 0x000000000000003f ElapsedTicks: 0x000000000c25bb00 IsRunning: false isRunning: false startTimeStamp: 0x000017dd204bbdb0stopwatch4{System.Diagnostics.Stopwatch} elapsed: 0x00000000164bec10 Elapsed: {00:00:00.1171879} ElapsedMilliseconds: 0x0000000000000075 ElapsedTicks: 0x00000000164bec10 IsRunning: false isRunning: false startTimeStamp: 0x000017dd2c7186b0

 

We can see that,the Method 3 is highly-efficient.