openCV - 5~7 图像混合、调整图像亮度与对比度、绘制形状与文字

5. 图像混合

理论-线性混合操作、相关API（addWeighted）

理论-线性混合操作

用到的公式 （其中 α 的取值范围为0~1之间）

相关API（addWeighted）

参数1：输入图像Mat – src1

参数2：输入图像src1的alpha值

参数3：输入图像Mat – src2

参数4：输入图像src2的alpha值

参数5：gamma值

参数6：输出混合图像

注意点：两张图像的大小和类型必须一致才可以

代码演示

#include <opencv2/opencv.hpp>
#include <iostream>

using namespace std;
using namespace cv;

int main(int argc, char** argv) {
  Mat src1, src2, dest;
	src1 = imread("D:/vcprojects/images/LinuxLogo.jpg");
	src2 = imread("D:/vcprojects/images/win7logo.jpg");
	if (!src1.data) {
		printf("could not load LinuxLogo image...\n");
		return -1;
	}
	if (!src2.data) {
		printf("could not load win7logo image...\n");
		return -1;
	}
	if (src1.rows == src2.rows && src1.cols == src2.cols) {
		double alpha = 0.5;
		namedWindow("line-blend", CV_WINDOW_AUTOSIZE);
		addWeighted(src1, (1 - alpha), src2, alpha, 0.0, dest);

		imshow("line-blend", dest);
		waitKey(0);
		return 0;
	}
	else {
		printf("image size is not same...\n");
		return -1;
	}
}

6. 调整图像亮度与对比度

理论

图像变换可以看作如下：

• 像素变换 – 点操作

• 邻域操作 – 区域

  调整图像亮度和对比度属于像素变换 - 点操作

重要的api

• Mat new_image = Mat::zeros( image.size(), image.type() ); 创建一张跟原图像大小和类型一致的空白图像、像素值初始化为0
• saturate_cast<uchar>(value)确保值大小范围为0~255之间
• Mat.at<Vec3b>(y,x)[index]=value 给每个像素点每个通道赋值

代码演示

#include <opencv2/opencv.hpp>
#include <iostream>

using namespace cv;
int main(int argc, char** argv) {
	Mat src, dst;
	src = imread("D:/vcprojects/images/test.png");
	if (!src.data) {
		printf("could not load image...\n");
		return -1;
	}
	char input_win[] = "input image";
	cvtColor(src, src, CV_BGR2GRAY);
	namedWindow(input_win, CV_WINDOW_AUTOSIZE);
	imshow(input_win, src);

	// contrast and brigthtness changes
	int height = src.rows;
	int width = src.cols;
	dst = Mat::zeros(src.size(), src.type());
	float alpha = 1.2;
	float beta = 30;

	Mat m1;
	src.convertTo(m1, CV_32F);
	for (int row = 0; row < height; row++) {
		for (int col = 0; col < width; col++) {
			if (src.channels() == 3) {
				float b = m1.at<Vec3f>(row, col)[0];// blue
				float g = m1.at<Vec3f>(row, col)[1]; // green
				float r = m1.at<Vec3f>(row, col)[2]; // red

				// output
				dst.at<Vec3b>(row, col)[0] = saturate_cast<uchar>(b*alpha + beta);
				dst.at<Vec3b>(row, col)[1] = saturate_cast<uchar>(g*alpha + beta);
				dst.at<Vec3b>(row, col)[2] = saturate_cast<uchar>(r*alpha + beta);
			}
			else if (src.channels() == 1) {
				float v = src.at<uchar>(row, col);
				dst.at<uchar>(row, col) = saturate_cast<uchar>(v*alpha + beta);
			}
		}
	}

	char output_title[] = "contrast and brightness change demo";
	namedWindow(output_title, CV_WINDOW_AUTOSIZE);
	imshow(output_title, dst);

	waitKey(0);
	return 0;
}

7. 绘制形状与文字

使用cv::Point与cv::Scalar、绘制线、矩形、园、椭圆等基本几何形状、随机生成与绘制文本

使用cv::Point与cv::Scalar

• Point表示2D平面上一个点x,y

  Point p;
  	p.x = 10;
  	p.y = 8;
   	or
  p = Pont(10,8);
  

• Scalar表示四个元素的向量

  Scalar(a, b, c);// a = blue, b = green, c = red表示RGB三个通道

绘制线、矩形、园、椭圆等基本几何形状

• 画线 cv::line （LINE_4\LINE_8\LINE_AA）
• 画椭圆cv::ellipse
• 画矩形cv::rectangle
• 画圆cv::circle
• 画填充cv::fillPoly

随机数生成cv::RNG

• 生成高斯随机数gaussian (double sigma)
• 生成正态分布随机数uniform (int a, int b)

绘制添加文字

putText函数 中设置fontFace(cv::HersheyFonts)

​ fontFace, CV_FONT_HERSHEY_PLAIN

​ fontScale , 1.0, 2.0~ 8.0

代码演示

#include <opencv2/opencv.hpp>
#include <iostream>

using namespace std;
using namespace cv;
Mat bgImage;
const char* drawdemo_win = "draw shapes and text demo";
void MyLines();
void MyRectangle();
void MyEllipse();
void MyCircle();
void MyPolygon();
void RandomLineDemo();
int main(int argc, char** argv) {
	bgImage = imread("D:/vcprojects/images/test1.png");
	if (!bgImage.data) {
		printf("could not load image...\n");
		return -1;
	}
	//MyLines();
	//MyRectangle();
	//MyEllipse();
	//MyCircle();
	//MyPolygon();

	//putText(bgImage, "Hello OpenCV", Point(300, 300), CV_FONT_HERSHEY_COMPLEX, 1.0, Scalar(12, 23, 200), 3, 8);
	//namedWindow(drawdemo_win, CV_WINDOW_AUTOSIZE);
	//imshow(drawdemo_win, bgImage);

	RandomLineDemo();
	waitKey(0);
	return 0;
}

void MyLines() {
	Point p1 = Point(20, 30);
	Point p2;
	p2.x = 400;
	p2.y = 400;
	Scalar color = Scalar(0, 0, 255);
	line(bgImage, p1, p2, color, 1, LINE_AA);
}

void MyRectangle() {
	Rect rect = Rect(200, 100, 300, 300);
	Scalar color = Scalar(255, 0, 0);
	rectangle(bgImage, rect, color, 2, LINE_8);
}

void MyEllipse() {
	Scalar color = Scalar(0, 255, 0);
	ellipse(bgImage, Point(bgImage.cols / 2, bgImage.rows / 2), Size(bgImage.cols / 4, bgImage.rows / 8), 90, 0, 360, color, 2, LINE_8);
}

void MyCircle() {
	Scalar color = Scalar(0, 255, 255);
	Point center = Point(bgImage.cols / 2, bgImage.rows / 2);
	circle(bgImage, center, 150, color, 2, 8);
}

void MyPolygon() {
	Point pts[1][5];
	pts[0][0] = Point(100, 100);
	pts[0][1] = Point(100, 200);
	pts[0][2] = Point(200, 200);
	pts[0][3] = Point(200, 100);
	pts[0][4] = Point(100, 100);

	const Point* ppts[] = { pts[0] };
	int npt[] = { 5 };
	Scalar color = Scalar(255, 12, 255);

	fillPoly(bgImage, ppts, npt, 1, color, 8);
}

void RandomLineDemo() {
	RNG rng(12345);
	Point pt1;
	Point pt2;
	Mat bg = Mat::zeros(bgImage.size(), bgImage.type());
	namedWindow("random line demo", CV_WINDOW_AUTOSIZE);
	for (int i = 0; i < 100000; i++) {
		pt1.x = rng.uniform(0, bgImage.cols);
		pt2.x = rng.uniform(0, bgImage.cols);
		pt1.y = rng.uniform(0, bgImage.rows);
		pt2.y = rng.uniform(0, bgImage.rows);
		Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255));
		if (waitKey(50) > 0) {
			break;
		}
		line(bg, pt1, pt2, color, 1, 8);
    // 生成随机彩线
		imshow("random line demo", bg);
	}
}

#include <opencv2/opencv.hpp>
#include <iostream>

using namespace cv;
static const char WINTITLE[] = "randomlines-demo";

int drawRandomLines(Mat image) {
	RNG rng(0xffffff);
	Point pt1, pt2;
	for (int i = 0; i < 100000; i++) {
		pt1.x = rng.uniform(0, image.cols);
		pt2.x = rng.uniform(0, image.cols);
		pt1.y = rng.uniform(0, image.rows);
		pt2.y = rng.uniform(0, image.rows);
		int r = rng.uniform(0, 255);
		int g = rng.uniform(0, 255);
		int b = rng.uniform(0, 255);
		line(image, pt1, pt2, Scalar(b, g, r), 1, LINE_8);
    // 添加文本
		putText(image, "Open CV Core Tutorial", Point(image.cols / 2-200, image.rows / 2),
			CV_FONT_HERSHEY_PLAIN, 2.0, Scalar(0, 255, 0), 3, LINE_8);

		imshow(WINTITLE, image);
		if (waitKey(10) >= 0)
		{
			return -1;
		}
	}
	return 0;
}

int main(int argc, char** argv) {
	Mat image = Mat::zeros(Size(450, 450), CV_8UC3);
	namedWindow(WINTITLE, CV_WINDOW_AUTOSIZE);
	int ok = drawRandomLines(image);
	if (ok != 0) {
		return 0;
	}
	return 0;
}