//參數說明：
//hDIB 圖像數據句柄
//n 對比增強的強度值
//函數說明：該函數實現圖像對比度增強的功能
HDIB DIB::ContrastEnhance(HANDLE hDIB,int n)
{	
	//用來保存數據
	HDIB hNewDIB;
	LPBITMAPINFOHEADER lpbi;
	//源數據區和新數據去指針
	LPBYTE lpSDIBBits,lpDDIBBits;
	int width,height,wBytesPerLine;
	if(!hDIB)
		return NULL;
	//得到每行圖像的字節數目
	wBytesPerLine = this->BytePerLine(hDIB);
	//鎖定數據區
	lpbi = (LPBITMAPINFOHEADER)GlobalLock(hDIB);
	width = lpbi->biWidth;
	height = lpbi->biHeight;
	lpSDIBBits = (LPBYTE)lpbi;
	//分配內存
	hNewDIB = GlobalAlloc(GHND,lpbi->biSize+lpbi->biSizeImage);
	if(!hNewDIB)
		return  NULL;
	lpDDIBBits = (LPBYTE)GlobalLock(hNewDIB);
	memcpy(lpDDIBBits,lpSDIBBits,lpbi->biSize);
	//使得兩個指針指向數據區開始位置
	lpSDIBBits = lpSDIBBits + lpbi->biSize;
	lpDDIBBits = lpDDIBBits + lpbi->biSize;
	BYTE rgb;
	long lOffset;
	for(int i=0;i<height;i++)
		for(int j=0;j<width;j++)
		{	
			//得到點在數據區中的偏移
			lOffset = this->PixelOffset(i,j,wBytesPerLine);
			//得到數據
			rgb = *(lpSDIBBits+lOffset);
			//對比度增強
			this->IncreaseContrast(&rgb,n);
			//保存數據
			*(lpDDIBBits+lOffset++) = rgb;
			*(lpDDIBBits+lOffset++) = rgb;
			*(lpDDIBBits+lOffset  ) = rgb;
		}
		GlobalUnlock(hDIB);
		GlobalUnlock(hNewDIB);
		return hNewDIB;
}

void DIB::IncreaseContrast(BYTE *pByte,int n)
{	
	//根據參數n來調節對比度，n越大，對比越強烈
	int Low = n;
	int High = 255-n;
	float Grad = ((float)(High-Low))/255;
	//數據很小，設置為0
	if(*pByte<=Low)
		*pByte = 0;
	//中間數據，進行對比增強處理
	else if ((Low<*pByte)&&(*pByte<High))
		*pByte = (BYTE)((*pByte-Low)/Grad);
	//數據很大，設置為255
	else
		*pByte = 255;
}