floodFill函数

floodFill函数

函数作用：

用指定颜色填充一个连接域

void cvFloodFill( CvArr* image, CvPoint seed_point, CvScalar new_val,
                  CvScalar lo_diff=cvScalarAll(0), CvScalar up_diff=cvScalarAll(0),
                  CvConnectedComp* comp=NULL, int flags=4, CvArr* mask=NULL );
#define CV_FLOODFILL_FIXED_RANGE (1 << 16)
#define CV_FLOODFILL_MASK_ONLY   (1 << 17)

image

输入的 1- 或 3-通道, 8-比特或浮点数图像。输入的图像将被函数的操作所改变，除非你选择 CV_ FLOODFILL_MASK_ONLY 选项 (见下面).

seed_point

开始的种子点.

new_val

新的重新绘制的象素值

lo_diff

当前观察象素值与其部件领域象素或者待加入该部件的种子象素之负差(Lower difference)的最大值。对 8-比特 彩色图像，它是一个 packed value.

up_diff

当前观察象素值与其部件领域象素或者待加入该部件的种子象素之正差(upper difference)的最大值。 对 8-比特 彩色图像，它是一个 packed value.

comp

指向部件结构体的指针，该结构体的内容由函数用重绘区域的信息填充。

flags

操作选项. 低位比特包含连通值, 4 (缺省) 或 8, 在函数执行连通过程中确定使用哪种邻域方式。高位比特可以是 0 或下面的开关选项的组合：

• CV_FLOODFILL_FIXED_RANGE - 如果设置，则考虑当前象素与种子象素之间的差，否则考虑当前象素与其相邻象素的差。(范围是浮点数).
• CV_FLOODFILL_MASK_ONLY - 如果设置，函数不填充原始图像 (忽略 new_val), 但填充掩模图像 (这种情况下 MASK 必须是非空的).

mask

运算掩模, 应该是单通道、8-比特图像, 长和宽上都比输入图像 image 大两个象素点。若非空，则函数使用且更新掩模, 所以使用者需对 mask 内容的初始化负责。填充不会经过 MASK 的非零象素, 例如，一个边缘检测子的输出可以用来作为 MASK 来阻止填充边缘。或者有可能在多次的函数调用中使用同一个 MASK，以保证填充的区域不会重叠。注意: 因为 MASK 比欲填充图像大，所以 mask 中与输入图像(x,y)像素点相对应的点具有(x+1,y+1)坐标。

函数 cvFloodFill 用指定颜色，从种子点开始填充一个连通域。连通性由象素值的接近程度来衡量。在点 (x, y) 的象素被认为是属于重新绘制的区域，如果：

src(x',y')-lo_diff<=src(x,y)<=src(x',y')+up_diff, 灰度图像，浮动范围

src(seed.x,seed.y)-lo<=src(x,y)<=src(seed.x,seed.y)+up_diff, 灰度图像，固定范围

src(x',y')r-lo_diffr<=src(x,y)r<=src(x',y')r+up_diffr 和

src(x',y')g-lo_diffg<=src(x,y)g<=src(x',y')g+up_diffg 和

src(x',y')b-lo_diffb<=src(x,y)b<=src(x',y')b+up_diffb, 彩色图像，浮动范围

src(seed.x,seed.y)r-lo_diffr<=src(x,y)r<=src(seed.x,seed.y)r+up_diffr 和

src(seed.x,seed.y)g-lo_diffg<=src(x,y)g<=src(seed.x,seed.y)g+up_diffg 和

src(seed.x,seed.y)b-lo_diffb<=src(x,y)b<=src(seed.x,seed.y)b+up_diffb, 彩色图像，固定范围

其中 src(x',y') 是象素邻域点的值。也就是说，为了被加入到连通域中，一个象素的彩色/亮度应该足够接近于：

• 它的邻域象素的彩色/亮度值，当该邻域点已经被认为属于浮动范围情况下的连通域。
• 固定范围情况下的种子点的彩色/亮度值

opencv代码：

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"

#include <iostream>

using namespace cv;
using namespace std;


//floodfill()
//Fills a connected component with the given color.

static void help()
{
	cout << "\nThis program demonstrated the floodFill() function\n"
		"Call:\n"
		"./ffilldemo [image_name -- Default: fruits.jpg]\n" << endl;

	cout << "Hot keys: \n"
		"\tESC - quit the program\n"
		"\tc - switch color/grayscale mode\n"
		"\tm - switch mask mode\n"
		"\tr - restore the original image\n"
		"\ts - use null-range floodfill\n"
		"\tf - use gradient floodfill with fixed(absolute) range\n"
		"\tg - use gradient floodfill with floating(relative) range\n"
		"\t4 - use 4-connectivity mode\n"
		"\t8 - use 8-connectivity mode\n" << endl;
}

Mat image0, image, gray, mask;
int ffillMode = 1;
int loDiff = 20, upDiff = 20;
int connectivity = 4;
int isColor = true;
bool useMask = false;
int newMaskVal = 255;

static void onMouse( int event, int x, int y, int, void* )
{
	if( event != CV_EVENT_LBUTTONDOWN )
		return;

	Point seed = Point(x,y);
	int lo = ffillMode == 0 ? 0 : loDiff;
	int up = ffillMode == 0 ? 0 : upDiff;
	int flags = connectivity + (newMaskVal << 8) +
		(ffillMode == 1 ? CV_FLOODFILL_FIXED_RANGE : 0);
	int b = (unsigned)theRNG() & 255;
	int g = (unsigned)theRNG() & 255;
	int r = (unsigned)theRNG() & 255;
	Rect ccomp;

	Scalar newVal = isColor ? Scalar(b, g, r) : Scalar(r*0.299 + g*0.587 + b*0.114);
	Mat dst = isColor ? image : gray;
	int area;

	if( useMask )
	{
		threshold(mask, mask, 1, 128, CV_THRESH_BINARY);
		area = floodFill(dst, mask, seed, newVal, &ccomp, Scalar(lo, lo, lo),
			Scalar(up, up, up), flags);
		imshow( "mask", mask );
	}
	else
	{
		area = floodFill(dst, seed, newVal, &ccomp, Scalar(lo, lo, lo),
			Scalar(up, up, up), flags);
	}

	imshow("image", dst);
	cout << area << " pixels were repainted\n";
}


int main( )
{
	char* filename="0.png";
	image0 = imread(filename, 1);

	if( image0.empty() )
	{
		cout << "Image empty. Usage: ffilldemo <image_name>\n";
		return 0;
	}
	help();
	image0.copyTo(image);
	cvtColor(image0, gray, CV_BGR2GRAY);
	mask.create(image0.rows+2, image0.cols+2, CV_8UC1);

	namedWindow( "image", 0 );
	createTrackbar( "lo_diff", "image", &loDiff, 255, 0 );
	createTrackbar( "up_diff", "image", &upDiff, 255, 0 );

	setMouseCallback( "image", onMouse, 0 );

	for(;;)
	{
		imshow("image", isColor ? image : gray);

		int c = waitKey(0);
		if( (c & 255) == 27 )
		{
			cout << "Exiting ...\n";
			break;
		}
		switch( (char)c )
		{
		case 'c':
			if( isColor )
			{
				cout << "Grayscale mode is set\n";
				cvtColor(image0, gray, CV_BGR2GRAY);
				mask = Scalar::all(0);
				isColor = false;
			}
			else
			{
				cout << "Color mode is set\n";
				image0.copyTo(image);
				mask = Scalar::all(0);
				isColor = true;
			}
			break;
		case 'm':
			if( useMask )
			{
				destroyWindow( "mask" );
				useMask = false;
			}
			else
			{
				namedWindow( "mask", 0 );
				mask = Scalar::all(0);
				imshow("mask", mask);
				useMask = true;
			}
			break;
		case 'r':
			cout << "Original image is restored\n";
			image0.copyTo(image);
			cvtColor(image, gray, CV_BGR2GRAY);
			mask = Scalar::all(0);
			break;
		case 's':
			cout << "Simple floodfill mode is set\n";
			ffillMode = 0;
			break;
		case 'f':
			cout << "Fixed Range floodfill mode is set\n";
			ffillMode = 1;
			break;
		case 'g':
			cout << "Gradient (floating range) floodfill mode is set\n";
			ffillMode = 2;
			break;
		case '4':
			cout << "4-connectivity mode is set\n";
			connectivity = 4;
			break;
		case '8':
			cout << "8-connectivity mode is set\n";
			connectivity = 8;
			break;
		}
	}

	return 0;
}