Opencv随手记（常用的一些小模块）

记录一些需要额外实现的小功能模块，以便之后复制粘贴，2333

 

四个点求解交点

cv::Point2f cross_Points(std::vector&points) {

	// cross point
	cv::Point2f cross_point;
	double y2_4 = points[1].y - points[3].y;
	double x1_3 = points[0].x - points[2].x;
	double y1_3 = points[0].y - points[2].y;
	double x2_4 = points[1].x - points[3].x;
	double y1_2 = points[0].y - points[1].y;
	double A = y2_4 * x1_3 - y1_3 * x2_4;
	std::cout << A << std::endl;

	if (A == 0)
		return cv::Point2f(0,0);
	double B = y2_4 * x1_3*points[1].x - y1_3 * x2_4*points[0].x + y1_2 * x2_4*x1_3;
	std::cout << B << std::endl;
	cross_point.x = B / A;
	cross_point.y = y1_3 / x1_3 * (cross_point.x - points[0].x) + points[0].y;
	std::cout << "交点坐标" << cross_point.x << " " << cross_point.y << std::endl;
	return cross_point;

}

二维旋转坐标计算（opencv好像只提供了整幅图像的矫正）

#include
#include
using namespace cv;
using namespace std;

cv::Point2f rotation_point2f(cv::Mat & rotation, cv::Point2f & point) {
	cv::Point2f result;
	result.x = rotation.at(0, 0) * point.x +
		rotation.at(0, 1) * point.y +
		rotation.at(0, 2);
	result.y = rotation.at(1, 0) * point.x +
		rotation.at(1, 1) * point.y +
		rotation.at(1, 2);
	return result;
}
int main() {
	double x = 1;
	double y = 1;
	double angle = x == 0 ? 0 : atan(y / x);
	cv::Mat rotation = cv::getRotationMatrix2D(cv::Point2f(50,50), angle / 3.14 * 180, 1.0);
	cv::Point2f point(50, 50);
	std::cout << rotation_point2f(rotation,point);
	std::system("pause");
}

opencv“绘制”中文汉字（仅限windows），效果如图：（无需typefree，会调用系统的中文字库）

opencv的putText不支持中文众所周知，之前写了一篇利用freetype“画”中文的文章太过冗余，下面这种方法在windows更方便。

#include 
#include 
#include 
using namespace cv;

void GetStringSize(HDC hDC, const char* str, int* w, int* h);
void putTextZH(cv::Mat &dst, const char* str, cv::Point org, cv::Scalar color, int fontSize,
	const char *fn = "Arial", bool italic = false, bool underline = false);
int main()
{

	cv::Mat img = cv::imread("1.jpg");
	const char *msg = "最英俊的人";
	putTextZH(img, msg, cv::Point(50, 50), cv::Scalar(0, 0, 255), 20);

	imshow("最英俊的人", img);
	cv::waitKey(-1);
	return 0;
}


void GetStringSize(HDC hDC, const char* str, int* w, int* h)
{
	SIZE size;
	GetTextExtentPoint32A(hDC, str, strlen(str), &size);
	if (w != 0) *w = size.cx;
	if (h != 0) *h = size.cy;
}

void putTextZH(Mat &dst, const char* str, Point org, Scalar color, int fontSize, const char* fn, bool italic, bool underline)
{
	CV_Assert(dst.data != 0 && (dst.channels() == 1 || dst.channels() == 3));

	int x, y, r, b;
	if (org.x > dst.cols || org.y > dst.rows) return;
	x = org.x < 0 ? -org.x : 0;
	y = org.y < 0 ? -org.y : 0;

	LOGFONTA lf;
	lf.lfHeight = -fontSize;
	lf.lfWidth = 0;
	lf.lfEscapement = 0;
	lf.lfOrientation = 0;
	lf.lfWeight = 5;
	lf.lfItalic = italic;   //斜体
	lf.lfUnderline = underline; //下划线
	lf.lfStrikeOut = 0;
	lf.lfCharSet = DEFAULT_CHARSET;
	lf.lfOutPrecision = 0;
	lf.lfClipPrecision = 0;
	lf.lfQuality = PROOF_QUALITY;
	lf.lfPitchAndFamily = 0;
	strcpy_s(lf.lfFaceName, fn);

	HFONT hf = CreateFontIndirectA(&lf);
	HDC hDC = CreateCompatibleDC(0);
	HFONT hOldFont = (HFONT)SelectObject(hDC, hf);

	int strBaseW = 0, strBaseH = 0;
	int singleRow = 0;
	char buf[1 << 12];
	strcpy_s(buf, str);
	char *bufT[1 << 12];  // 这个用于分隔字符串后剩余的字符，可能会超出。
						  //处理多行
	{
		int nnh = 0;
		int cw, ch;

		const char* ln = strtok_s(buf, "\n", bufT);
		while (ln != 0)
		{
			GetStringSize(hDC, ln, &cw, &ch);
			strBaseW = max(strBaseW, cw);
			strBaseH = max(strBaseH, ch);

			ln = strtok_s(0, "\n", bufT);
			nnh++;
		}
		singleRow = strBaseH;
		strBaseH *= nnh;
	}

	if (org.x + strBaseW < 0 || org.y + strBaseH < 0)
	{
		SelectObject(hDC, hOldFont);
		DeleteObject(hf);
		DeleteObject(hDC);
		return;
	}

	r = org.x + strBaseW > dst.cols ? dst.cols - org.x - 1 : strBaseW - 1;
	b = org.y + strBaseH > dst.rows ? dst.rows - org.y - 1 : strBaseH - 1;
	org.x = org.x < 0 ? 0 : org.x;
	org.y = org.y < 0 ? 0 : org.y;

	BITMAPINFO bmp = { 0 };
	BITMAPINFOHEADER& bih = bmp.bmiHeader;
	int strDrawLineStep = strBaseW * 3 % 4 == 0 ? strBaseW * 3 : (strBaseW * 3 + 4 - ((strBaseW * 3) % 4));

	bih.biSize = sizeof(BITMAPINFOHEADER);
	bih.biWidth = strBaseW;
	bih.biHeight = strBaseH;
	bih.biPlanes = 1;
	bih.biBitCount = 24;
	bih.biCompression = BI_RGB;
	bih.biSizeImage = strBaseH * strDrawLineStep;
	bih.biClrUsed = 0;
	bih.biClrImportant = 0;

	void* pDibData = 0;
	HBITMAP hBmp = CreateDIBSection(hDC, &bmp, DIB_RGB_COLORS, &pDibData, 0, 0);

	CV_Assert(pDibData != 0);
	HBITMAP hOldBmp = (HBITMAP)SelectObject(hDC, hBmp);

	//color.val[2], color.val[1], color.val[0]
	SetTextColor(hDC, RGB(255, 255, 255));
	SetBkColor(hDC, 0);
	//SetStretchBltMode(hDC, COLORONCOLOR);

	strcpy_s(buf, str);
	const char* ln = strtok_s(buf, "\n", bufT);
	int outTextY = 0;
	while (ln != 0)
	{
		TextOutA(hDC, 0, outTextY, ln, strlen(ln));
		outTextY += singleRow;
		ln = strtok_s(0, "\n", bufT);
	}
	uchar* dstData = (uchar*)dst.data;
	int dstStep = dst.step / sizeof(dstData[0]);
	unsigned char* pImg = (unsigned char*)dst.data + org.x * dst.channels() + org.y * dstStep;
	unsigned char* pStr = (unsigned char*)pDibData + x * 3;
	for (int tty = y; tty <= b; ++tty)
	{
		unsigned char* subImg = pImg + (tty - y) * dstStep;
		unsigned char* subStr = pStr + (strBaseH - tty - 1) * strDrawLineStep;
		for (int ttx = x; ttx <= r; ++ttx)
		{
			for (int n = 0; n < dst.channels(); ++n) {
				double vtxt = subStr[n] / 255.0;
				int cvv = vtxt * color.val[n] + (1 - vtxt) * subImg[n];
				subImg[n] = cvv > 255 ? 255 : (cvv < 0 ? 0 : cvv);
			}

			subStr += 3;
			subImg += dst.channels();
		}
	}

	SelectObject(hDC, hOldBmp);
	SelectObject(hDC, hOldFont);
	DeleteObject(hf);
	DeleteObject(hBmp);
	DeleteDC(hDC);
}