图像二直化之一种快速自适应图像二值化算法(Wellner 1993)

A fast adaptive image binarization method (Wellner 1993)

该算法的英文介绍可看：http://www.idevlife.com/24638/

原文下载地址：不过好像下不下来了。

http://www.xrce.xerox.com/Publications/Attachments/1993-110/EPC-1993-110.pdf

该算法的主要思想如下：

代码如下：

void quickAdaptiveThreshold(unsigned char* grayImage, unsigned char* binImage,int width,int height)
{

	int t = 15; 
	int s = width >> 3; 
	const int T = 9; //T是避免浮点数运算
	const int power2S = 1 << T; //同时乘除2的T次方,避免浮点运算
	
	int factor = power2S * (100-t) / (100*s); 
	int gn = 127 * s; 
	int q = power2S - power2S / s; //等比数列比率
	int pn, hn;
	unsigned char *scanline = NULL;
	int *prev_gn = NULL;

	prev_gn = new int[width];
	for (int i = 0; i < width; i++) 
	{
		prev_gn[i] = gn;
	}
	
	//左右交替扫描所有行
	for (int y = 0; y < height; y ++ )
	{
		int yh = y * width;
		scanline = grayImage + y * width;
		for ( int x = 0; x > T) + pn; 
			hn = (gn + prev_gn[x]) >> 1;     //上下两行求平均
			prev_gn[x] = gn; 		
			pn < (hn*factor) >> T ? binImage[yh+x] = 0 : binImage[yh+x] = 0xff;
		}
		y ++ ;
		if ( y == height)
		{
			break;
		}
		yh = y * width;
		scanline = grayImage + y * width;
		for ( int x = width-1; x >= 0; x --)  //该行从右往左扫描
		{
			pn = scanline[x] ;
			gn = ((gn * q) >> T) + pn; 
			hn = (gn + prev_gn[x]) >> 1;
			prev_gn[x] = gn; 		
			pn < (hn*factor) >> T ? binImage[yh+x] = 0 : binImage[yh+x] = 0xff;
		}
	}

	delete prev_gn;
}

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