四 指针法
C/C++的习惯,不是C#的特点
public static Bitmap RGB2Gray(Bitmap srcBitmap)
{
int wide = srcBitmap.Width;
int height = srcBitmap.Height ;
Rectangle rect = new Rectangle(0, 0, wide, height);
BitmapData srcBmData = srcBitmap.LockBits(rect,
ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
Bitmap dstBitmap = CreateGrayscaleImage(wide, height);
BitmapData dstBmData = dstBitmap.LockBits(rect,
ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);
System.IntPtr srcScan = srcBmData.Scan0;
System.IntPtr dstScan = dstBmData.Scan0;
Unsafe //启动不安全代码
{
byte* srcP = (byte*)(void*) srcScan;
byte* dstP = (byte*)(void*) dstScan;
int srcOffset = srcBmData.Stride - wide * 3;
int dstOffset = dstBmData.Stride - wide ;
byte red, green, blue;
for (int y = 0; y < height; y++)
{
for (int x = 0; x <wide ; x++, srcP += 3, dstP++)
{
blue = srcP [0];
green = srcP [1];
red = srcP [2];
* dstP = (byte)(.299 * red + .587 * green + .114 * blue);
}
srcP += srcOffset;
dstP += dstOffset;
}
}
srcBitmap.UnlockBits(srcBmData);
dstBitmap.UnlockBits(dstBmData );
return dstBitmap;
}//#
五. 矩阵法
并不是什么新方法,只是将图像数据分做R,G,B三个矩阵(二维数组)存储,类似MATLAB的习惯.
public static bool GetRGB(Bitmap Source, out int[,] R, out int[,] G, out int[,] B)
{
try
{
int iWidth = Source.Width;
int iHeight = Source.Height;
Rectangle rect = new Rectangle(0, 0, iWidth, iHeight);
System.Drawing.Imaging.BitmapData bmpData = Source.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite, Source.PixelFormat);
IntPtr iPtr = bmpData.Scan0;
int iBytes = iWidth * iHeight * 3;
byte[] PixelValues = new byte[iBytes];
System.Runtime.InteropServices.Marshal.Copy(iPtr, PixelValues, 0, iBytes);
Source.UnlockBits(bmpData);
// 注意这个地方图像的两维方向与数组两维的方向是转置的关系
R = new int[iHeight, iWidth];
G = new int[iHeight, iWidth];
B = new int[iHeight, iWidth];
int iPoint = 0;
for (int i = 0; i < iHeight; i++)
{
for (int j = 0; j < iWidth; j++)
{
// 注意，Windows 中三基色的排列顺序是 BGR 而不是 RGB！
B[i, j] = Convert.ToInt32(PixelValues[iPoint++]);
G[i, j] = Convert.ToInt32(PixelValues[iPoint++]);
R[i, j] = Convert.ToInt32(PixelValues[iPoint++]);
}
}
return true;
}
catch (Exception)
{
R = null;
G = null;
B = null;
return false;
}
}//#
public static Bitmap FromRGB(int[,] R, int[,] G, int[,] B)
{
int iWidth = G.GetLength(1);
int iHeight = G.GetLength(0);
Bitmap Result = new Bitmap(iWidth, iHeight, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
Rectangle rect = new Rectangle(0, 0, iWidth, iHeight);
System.Drawing.Imaging.BitmapData bmpData = Result.LockBits(rect, System.Drawing.Imaging.ImageLockMode.ReadWrite, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
IntPtr iPtr = bmpData.Scan0;
int iStride = bmpData.Stride;
int iBytes = iWidth * iHeight * 3;
byte[] PixelValues = new byte[iBytes];
int iPoint = 0;
for (int i = 0; i < iHeight; i++)
for (int j = 0; j < iWidth; j++)
{
int iG = G[i, j];
int iB = B[i, j];
int iR = R[i, j];
PixelValues[iPoint] = Convert.ToByte(iB);
PixelValues[iPoint + 1] = Convert.ToByte(iG);
PixelValues[iPoint + 2] = Convert.ToByte(iR);
iPoint += 3;
}
System.Runtime.InteropServices.Marshal.Copy(PixelValues, 0, iPtr, iBytes);
Result.UnlockBits(bmpData);
return Result;
}//#
public static bool GetGray(Bitmap srcBitmap, out byte [,] gray)
{
Bitmap tempBitmap;
if (srcBitmap.PixelFormat != PixelFormat.Format8bppIndexed)
tempBitmap = ImageProcess.Image.Gray(srcBitmap);
else
tempBitmap = srcBitmap;
int wide = tempBitmap.Width;
int height = tempBitmap.Height;
gray = new byte [height, wide];
BitmapData gbmData = tempBitmap.LockBits(new Rectangle(0, 0, wide, height),
ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);
System.IntPtr ScanG = gbmData.Scan0;
int gOffset = gbmData.Stride - wide;
unsafe
{
byte* g = (byte*)(void*)ScanG;
// for each pixel
for (int y = 0; y < height; y++)
{
// for each pixel
for (int x = 0; x < wide; x++, g++)
{
gray[y ,x ] =*g;
}
g += gOffset;
}
}
tempBitmap.UnlockBits(gbmData);
return true ;
}//#
public static Bitmap FromGray(byte [,] Gray)
{
int iWidth = Gray.GetLength(1);
int iHeight = Gray.GetLength(0);
Bitmap dstBitmap = ImageProcess.Image.CreateGrayscaleImage(iWidth, iHeight);
BitmapData gbmData = dstBitmap.LockBits(new Rectangle(0, 0, iWidth, iHeight),
ImageLockMode.ReadWrite, PixelFormat.Format8bppIndexed);
System.IntPtr ScanG = gbmData.Scan0;
int gOffset = gbmData.Stride - iWidth;
unsafe
{
byte* g = (byte*)(void*)ScanG;
// 注意这个地方图像的两维方向与数组两维的方向是转置的关系
for (int i = 0; i < iHeight; i++)
{
for (int j = 0; j < iWidth; j++)
{
*g=(byte )Gray[i, j] ;
g++;
}
g += gOffset;
}
}
dstBitmap.UnlockBits(gbmData);
return dstBitmap;
} //#
/*********************************补充******************************************/
/// <summary> /// Create and initialize grayscale image
/// </summary>
public static Bitmap CreateGrayscaleImage( int width, int height )
{
// create new image
Bitmap bmp = new Bitmap( width, height, PixelFormat.Format8bppIndexed );
// set palette to grayscale
SetGrayscalePalette( bmp );
// return new image
return bmp;
}//#
/// <summary>
/// Set pallete of the image to grayscale
/// </summary>
public static void SetGrayscalePalette( Bitmap srcImg )
{
// check pixel format
if ( srcImg.PixelFormat != PixelFormat.Format8bppIndexed )
throw new ArgumentException( );
// get palette
ColorPalette cp = srcImg.Palette;
// init palette
for ( int i = 0; i < 256; i++ )
{
cp.Entries[i] = Color.FromArgb( i, i, i );
}
// set palette back
srcImg.Palette = cp;
}//#
/*********************************END********************************************/
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