在对Bitmap图片操作的时候，有时需要用到获取或设置像素颜色方法：GetPixel 和 SetPixel，
如果直接对这两个方法进行操作的话速度很慢，这里我们可以通过把数据提取出来操作，然后操作完在复制回去可以加快访问速度
其实对Bitmap的访问还有两种方式，一种是内存法，一种是指针法
1、内存法
这里定义一个类LockBitmap，通过把Bitmap数据拷贝出来，在内存上直接操作，操作完成后在拷贝到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 bitmap
Width = source.Width;
Height = source.Height; // get total locked pixels count
int PixelCount = Width * Height; // Create rectangle to lock
Rectangle rect = new Rectangle(, , 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 != && Depth != && Depth != )
{
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 / ;
Pixels = new byte[PixelCount * step];
Iptr = bitmapData.Scan0; // Copy data from pointer to array
Marshal.Copy(Iptr, Pixels, , 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, , 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 / ; // Get start index of the specified pixel
int i = ((y * Width) + x) * cCount; if (i > Pixels.Length - cCount)
throw new IndexOutOfRangeException(); if (Depth == ) // For 32 bpp get Red, Green, Blue and Alpha
{
byte b = Pixels[i];
byte g = Pixels[i + ];
byte r = Pixels[i + ];
byte a = Pixels[i + ]; // a
clr = Color.FromArgb(a, r, g, b);
}
if (Depth == ) // For 24 bpp get Red, Green and Blue
{
byte b = Pixels[i];
byte g = Pixels[i + ];
byte r = Pixels[i + ];
clr = Color.FromArgb(r, g, b);
}
if (Depth == )
// 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 / ; // Get start index of the specified pixel
int i = ((y * Width) + x) * cCount; if (Depth == ) // For 32 bpp set Red, Green, Blue and Alpha
{
Pixels[i] = color.B;
Pixels[i + ] = color.G;
Pixels[i + ] = color.R;
Pixels[i + ] = color.A;
}
if (Depth == ) // For 24 bpp set Red, Green and Blue
{
Pixels[i] = color.B;
Pixels[i + ] = color.G;
Pixels[i + ] = color.R;
}
if (Depth == )
// For 8 bpp set color value (Red, Green and Blue values are the same)
{
Pixels[i] = color.B;
}
}
}
使用：先锁定Bitmap，然后通过Pixels操作颜色对象，最后释放锁，把数据更新到Bitmap中
string file = @"C:\test.jpg";
Bitmap bmp = new Bitmap(Image.FromFile(file)); LockBitmap lockbmp = new LockBitmap(bmp);
//锁定Bitmap，通过Pixel访问颜色
lockbmp.LockBits(); //获取颜色
Color color = lockbmp.GetPixel(, ); //从内存解锁Bitmap
lockbmp.UnlockBits();
2、指针法
这种方法访问速度比内存法更快，直接通过指针对内存进行操作，不需要进行拷贝，但是在C#中直接通过指针操作内存是不安全的，所以需要在代码中加入unsafe关键字，在生成选项中把允许不安全代码勾上，才能编译通过
这里定义成PointerBitmap类
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 bitmap
Width = source.Width;
Height = source.Height; // get total locked pixels count
int PixelCount = Width * Height; // Create rectangle to lock
Rectangle rect = new Rectangle(, , 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 != && Depth != && Depth != )
{
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); //得到首地址
unsafe
{
Iptr = bitmapData.Scan0;
//二维图像循环 }
}
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 / ;
Color c = Color.Empty;
if (Depth == )
{
int a = ptr[];
int r = ptr[];
int g = ptr[];
int b = ptr[];
c = Color.FromArgb(a, r, g, b);
}
else if (Depth == )
{
int r = ptr[];
int g = ptr[];
int b = ptr[];
c = Color.FromArgb(r, g, b);
}
else if (Depth == )
{
int r = ptr[];
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 / ;
if (Depth == )
{
ptr[] = c.A;
ptr[] = c.R;
ptr[] = c.G;
ptr[] = c.B;
}
else if (Depth == )
{
ptr[] = c.R;
ptr[] = c.G;
ptr[] = c.B;
}
else if (Depth == )
{
ptr[] = c.R;
ptr[] = c.G;
ptr[] = c.B;
}
}
}
}
使用方法这里就不列出来了，跟上面的LockBitmap类似
以上图片由“图斗罗”提供