Learning OpenCV Chapter3 初探OpenCV下

1. 矩陣和圖像操作

Learning OpenCV中描述的都是OpenCV1.1的特徵，已經遠遠落後於如今的2.4.9版本，這期間OpenCV有了很多新特性，比如說Mat.

矩陣和圖像操作這一部分詳細的介紹了一些適用於CvMat，圖像處理中的基本操作，例如對角化，矩陣變換，以及更復雜的諸如計算圖像的統計操作。但是鑑於新的OpenCV中已經有了Mat結構，可以方便的進行內存管理，不用主動釋放內存，方便寫更大的程序，所以我就不列舉書中所介紹的各種CvMat的基本操作，不過推薦閱讀OpenCV的Documentation，裏面對於基本數據結構以及相應函數的介紹很全面，也推薦閱讀這篇文章的介紹。

繪圖

下面介紹OpenCV的一些基本繪圖函數，詳情請參考官方文檔

<span style="font-size:14px;">//繪製直線(畫布，端點1，端點2，顏色（BGRA）,線條粗細，反走樣模式
	void line(CV_IN_OUT Mat& img, Point pt1, Point pt2, 
						  const Scalar& color,int thickness=1, 
						  int lineType=8, int shift=0);

	void rectangle(CV_IN_OUT Mat& img, Point pt1, Point pt2,
                          const Scalar& color, int thickness=1,
                          int lineType=8, int shift=0);
	
	void circle(CV_IN_OUT Mat& img, Point center, int radius,
                       const Scalar& color, int thickness=1,
                       int lineType=8, int shift=0);

	void ellipse(CV_IN_OUT Mat& img, Point center, Size axes,
                        double angle, double startAngle, double endAngle,
                        const Scalar& color, int thickness=1,
                        int lineType=8, int shift=0);

	void ellipse(CV_IN_OUT Mat& img, const RotatedRect& box, const Scalar& color,
                        int thickness=1, int lineType=8);

	void fillConvexPoly(Mat& img, const Point* pts, int npts,
                               const Scalar& color, int lineType=8,
                               int shift=0);
	
	void fillConvexPoly(InputOutputArray img, InputArray points,
                                 const Scalar& color, int lineType=8,
                                 int shift=0);

	void fillPoly(Mat& img, const Point** pts,
                         const int* npts, int ncontours,
                         const Scalar& color, int lineType=8, int shift=0,
                         Point offset=Point() );

	void fillPoly(InputOutputArray img, InputArrayOfArrays pts,
                           const Scalar& color, int lineType=8, int shift=0,
                           Point offset=Point() );

	void polylines(Mat& img, const Point** pts, const int* npts,
                          int ncontours, bool isClosed, const Scalar& color,
                          int thickness=1, int lineType=8, int shift=0 );

	void polylines(InputOutputArray img, InputArrayOfArrays pts,
                            bool isClosed, const Scalar& color,
                            int thickness=1, int lineType=8, int shift=0 );
	
	void putText( Mat& img, const string& text, Point org,
                         int fontFace, double fontScale, Scalar color,
                         int thickness=1, int lineType=8,
                         bool bottomLeftOrigin=false );

	Size getTextSize(const string& text, int fontFace,
                            double fontScale, int thickness,
                            CV_OUT int* baseLine);
</span>

不妨看一個有趣的官方示例代碼

<span style="font-size:14px;">#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <stdio.h>
using namespace cv;

static void help()
{
    printf("\nThis program demonstrates OpenCV drawing and text output functions.\n");
}
static Scalar randomColor(RNG& rng)
{
    int icolor = (unsigned)rng;
	//隨機返回顏色
    return Scalar(icolor&255, (icolor>>8)&255, (icolor>>16)&255);
}

int main()
{
    help();
    char wndname[] = "Drawing Demo";
    const int NUMBER = 100;
    const int DELAY = 5;
	//反走樣模式，CV_AA最高，其次還有lineType = 8 或 lineType = 4
    int lineType = CV_AA; 
    int i, width = 1000, height = 700;
    int x1 = -width/2, x2 = width*3/2, y1 = -height/2, y2 = height*3/2;
	//隨機數生成器
    RNG rng(0xFFFFFFFF);

    Mat image = Mat::zeros(height, width, CV_8UC3);
    imshow(wndname, image);
    waitKey(DELAY);

    for (i = 0; i < NUMBER; i++)
    {
        Point pt1, pt2;
        pt1.x = rng.uniform(x1, x2);
        pt1.y = rng.uniform(y1, y2);
        pt2.x = rng.uniform(x1, x2);
        pt2.y = rng.uniform(y1, y2);

		//繪製直線
        line( image, pt1, pt2, randomColor(rng), rng.uniform(1,10), lineType );

        imshow(wndname, image);
        if(waitKey(DELAY) >= 0)
            return 0;
    }

    for (i = 0; i < NUMBER; i++)
    {
        Point pt1, pt2;
        pt1.x = rng.uniform(x1, x2);
        pt1.y = rng.uniform(y1, y2);
        pt2.x = rng.uniform(x1, x2);
        pt2.y = rng.uniform(y1, y2);
        int thickness = rng.uniform(-3, 10);
		
		//繪製矩形
        rectangle( image, pt1, pt2, randomColor(rng), MAX(thickness, -1), lineType );

        imshow(wndname, image);
        if(waitKey(DELAY) >= 0)
            return 0;
    }

    for (i = 0; i < NUMBER; i++)
    {
        Point center;
        center.x = rng.uniform(x1, x2);
        center.y = rng.uniform(y1, y2);
        Size axes;
        axes.width = rng.uniform(0, 200);
        axes.height = rng.uniform(0, 200);
        double angle = rng.uniform(0, 180);

		//繪製橢圓
        ellipse( image, center, axes, angle, angle - 100, angle + 200,
                 randomColor(rng), rng.uniform(-1,9), lineType );

        imshow(wndname, image);
        if(waitKey(DELAY) >= 0)
            return 0;
    }

    for (i = 0; i< NUMBER; i++)
    {
        Point pt[2][3];
        pt[0][0].x = rng.uniform(x1, x2);
        pt[0][0].y = rng.uniform(y1, y2);
        pt[0][1].x = rng.uniform(x1, x2);
        pt[0][1].y = rng.uniform(y1, y2);
        pt[0][2].x = rng.uniform(x1, x2);
        pt[0][2].y = rng.uniform(y1, y2);
        pt[1][0].x = rng.uniform(x1, x2);
        pt[1][0].y = rng.uniform(y1, y2);
        pt[1][1].x = rng.uniform(x1, x2);
        pt[1][1].y = rng.uniform(y1, y2);
        pt[1][2].x = rng.uniform(x1, x2);
        pt[1][2].y = rng.uniform(y1, y2);
        const Point* ppt[2] = {pt[0], pt[1]};
        int npt[] = {3, 3};

		//繪製多條多邊形曲線（這裏是兩條）
        polylines(image, ppt, npt, 2, true, randomColor(rng), rng.uniform(1,10), lineType);

        imshow(wndname, image);
        if(waitKey(DELAY) >= 0)
			return 0;
    }

    for (i = 0; i< NUMBER; i++)
    {
        Point pt[2][3];
        pt[0][0].x = rng.uniform(x1, x2);
        pt[0][0].y = rng.uniform(y1, y2);
        pt[0][1].x = rng.uniform(x1, x2);
        pt[0][1].y = rng.uniform(y1, y2);
        pt[0][2].x = rng.uniform(x1, x2);
        pt[0][2].y = rng.uniform(y1, y2);
        pt[1][0].x = rng.uniform(x1, x2);
        pt[1][0].y = rng.uniform(y1, y2);
        pt[1][1].x = rng.uniform(x1, x2);
        pt[1][1].y = rng.uniform(y1, y2);
        pt[1][2].x = rng.uniform(x1, x2);
        pt[1][2].y = rng.uniform(y1, y2);
        const Point* ppt[2] = {pt[0], pt[1]};
        int npt[] = {3, 3};

		//同時繪製多個多邊形，這裏是兩個
        fillPoly(image, ppt, npt, 2, randomColor(rng), lineType);

        imshow(wndname, image);
        if(waitKey(DELAY) >= 0)
            return 0;
    }

    for (i = 0; i < NUMBER; i++)
    {
        Point center;
        center.x = rng.uniform(x1, x2);
        center.y = rng.uniform(y1, y2);

		//繪製圓
        circle(image, center, rng.uniform(0, 300), randomColor(rng),
               rng.uniform(-1, 9), lineType);

        imshow(wndname, image);
        if(waitKey(DELAY) >= 0)
            return 0;
    }

    for (i = 1; i < NUMBER; i++)
    {
        Point org;
        org.x = rng.uniform(x1, x2);
        org.y = rng.uniform(y1, y2);

		//顯示文字
        putText(image, "Testing text rendering", org, rng.uniform(0,8),
                rng.uniform(0,100)*0.05+0.1, randomColor(rng), rng.uniform(1, 10), lineType);

        imshow(wndname, image);
        if(waitKey(DELAY) >= 0)
            return 0;
    }

	//獲取字符串的尺寸
    Size textsize = getTextSize("OpenCV forever!", FONT_HERSHEY_COMPLEX, 3, 5, 0);
    Point org((width - textsize.width)/2, (height - textsize.height)/2);

    Mat image2;
    for( i = 0; i < 255; i += 2 )
    {
        image2 = image - Scalar::all(i);
        putText(image2, "OpenCV forever!", org, FONT_HERSHEY_COMPLEX, 3,
                Scalar(i, i, 255), 5, lineType);

        imshow(wndname, image2);
        if(waitKey(DELAY) >= 0)
            return 0;
    }

    waitKey();
    return 0;
}

#ifdef _EiC
main(1,"drawing.c");
#endif
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