在對Bitmap圖片操作的時候，有時需要用到獲取或設置像素顏色方法：GetPixel 和 SetPixel，

如果直接對這兩個方法進行操作的話速度很慢，這里我們可以通過把數據提取出來操作，然后操作完在復制回去可以加快訪問速度

其實對Bitmap的訪問還有兩種方式，一種是內存法，一種是指針法

1、內存法

　　這里定義一個類LockBitmap，通過把Bitmap數據拷貝出來，在內存上直接操作，操作完成后在拷貝到Bitmap中

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 bitmapWidth = source.Width;Height = source.Height;// get total locked pixels countint PixelCount = Width * Height;// Create rectangle to lockRectangle rect = new Rectangle(0, 0, Width, Height);// get source bitmap pixel format sizeDepth = System.Drawing.Bitmap.GetPixelFormatSize(source.PixelFormat);// Check if bpp (Bits Per Pixel) is 8, 24, or 32if (Depth != 8 && Depth != 24 && Depth != 32){throw new ArgumentException("Only 8, 24 and 32 bpp images are supported.");}// Lock bitmap and return bitmap databitmapData = source.LockBits(rect, ImageLockMode.ReadWrite,source.PixelFormat);// create byte array to copy pixel valuesint step = Depth / 8;Pixels = new byte[PixelCount * step];Iptr = bitmapData.Scan0;// Copy data from pointer to arrayMarshal.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 pointerMarshal.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 countint cCount = Depth / 8;// Get start index of the specified pixelint 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]; // aclr = 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 countint cCount = Depth / 8;// Get start index of the specified pixelint 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;}}}
　　使用：先鎖定Bitmap，然后通過Pixels操作顏色對象，最后釋放鎖，把數據更新到Bitmap中 string file = @"C:\test.jpg";Bitmap bmp = new Bitmap(Image.FromFile(file));LockBitmap lockbmp = new LockBitmap(bmp);//鎖定Bitmap，通過Pixel訪問顏色 lockbmp.LockBits();//獲取顏色Color color = lockbmp.GetPixel(10, 10);//從內存解鎖Bitmaplockbmp.UnlockBits();

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2、指針法這種方法訪問速度比內存法更快，直接通過指針對內存進行操作，不需要進行拷貝，但是在C#中直接通過指針操作內存是不安全的，所以需要在代碼中加入unsafe關鍵字，在生成選項中把允許不安全代碼勾上，才能編譯通過這里定義成PointerBitmap類 public class PointBitmap{Bitmap source = null;IntPtr Iptr = IntPtr.Zero;BitmapData bitmapData = null;public int Depth { get; private set; }public int Width { get; private set; }public int Height { get; private set; }public PointBitmap(Bitmap source){this.source = source;}public void LockBits(){try{// Get width and height of bitmapWidth = source.Width;Height = source.Height;// get total locked pixels countint PixelCount = Width * Height;// Create rectangle to lockRectangle rect = new Rectangle(0, 0, Width, Height);// get source bitmap pixel format sizeDepth = System.Drawing.Bitmap.GetPixelFormatSize(source.PixelFormat);// Check if bpp (Bits Per Pixel) is 8, 24, or 32if (Depth != 8 && Depth != 24 && Depth != 32){throw new ArgumentException("Only 8, 24 and 32 bpp images are supported.");}// Lock bitmap and return bitmap databitmapData = source.LockBits(rect, ImageLockMode.ReadWrite,source.PixelFormat);//得到首地址unsafe{Iptr = bitmapData.Scan0;//二維圖像循環 }}catch (Exception ex){throw ex;}}public void UnlockBits(){try{source.UnlockBits(bitmapData);}catch (Exception ex){throw ex;}}public Color GetPixel(int x, int y){unsafe{byte* ptr = (byte*)Iptr;ptr = ptr + bitmapData.Stride * y;ptr += Depth * x / 8;Color c = Color.Empty;if (Depth == 32){int a = ptr[3];int r = ptr[2];int g = ptr[1];int b = ptr[0];c = Color.FromArgb(a, r, g, b);}else if (Depth == 24){int r = ptr[2];int g = ptr[1];int b = ptr[0];c = Color.FromArgb(r, g, b);}else if (Depth == 8){int r = ptr[0];c = Color.FromArgb(r, r, r);}return c;}}public void SetPixel(int x, int y, Color c){unsafe{byte* ptr = (byte*)Iptr;ptr = ptr + bitmapData.Stride * y;ptr += Depth * x / 8;if (Depth == 32){ptr[3] = c.A;ptr[2] = c.R;ptr[1] = c.G;ptr[0] = c.B;}else if (Depth == 24){ptr[2] = c.R;ptr[1] = c.G;ptr[0] = c.B;}else if (Depth == 8){ptr[2] = c.R;ptr[1] = c.G;ptr[0] = c.B;}}}}

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?使用方法這里就不列出來了，跟上面的LockBitmap類似

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https://blog.csdn.net/yangyikun0428/article/details/53771596

轉載于:https://www.cnblogs.com/dearzhoubi/p/8710365.html

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