调整图像亮度和对比度
理论
像素变换---点操作
邻域操作---区域
做图像的卷积，图像特征提取，图像梯度计算，图像更深入模式匹配，模糊，平滑等
调整图像亮度和对比度属于像素变换---点操作
g(i,j) = a*f(i,j)+P 其中a>0,P是增益变量
重要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
#include<opencv2/opencv.hpp>
#include<iostream>
using namespace cv;
int main(int argc,char** argv){
Mat src,dst;
src = imread();
if(!src.data){
printf("could not load image...\n");
return -1;
}
char input_win[] = "input image";
namedWindow(input_win,CV_WINDOW_AUTOSIZE);
imshow(input_win,src);
int height = src.rows;
int width = src.cols;
dst = Mat::zeros(src.size(),src.type());
float alpha = 1.2;
float beta = 30;
for(int row = 0; row < height; row++){
for(int col = 0; col < width; col++){
if(src.channels() == 3){
float b = src.at<Vec3b>(row,col)[0];
float g = src.at<Vec3b>(row,col)[1];
float r = src.at<Vec3b>(row,col)[2];
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<Vec3b>(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;
}
绘制形状与文字
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 = Point(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、圆、椭圆等基本几何形状
画线cv::line(LINE_4\LINE_8\LINE_AA)注意：LINE_AA反锯齿
画椭圆cv::ellipse
画矩形cv::rectangle
画圆cv::circle
画填充cv::fillPoly
随机生成与绘制文本
#include<opencv2/opencv.hpp>
#include<iostream>
using namespace std;
using namespace cv;
Mat bgImage;
const char* drawdemo_win = "draw shapes and text demo";
//画线
void MyLines();
//画矩形
void MyRectangle();
//画椭圆
void MyEllipse();
//画圆
void MyCircle();
//画多边形
void MyPolygen();
//画随机线
void RandomLineDemo();
int main(int argc,char** argv){
bgImage = imread("");
if(!bgImage.data){
cout<<"could not load image..."<<endl;
return -1;
}
MyLines();
MyRectangle();
MyEllipse();
MyCircle();
MyPolygen();
//输出文字
putText(bgImage,"Hello OpenCV",Point(300,300),CV_FONT_HERSHEY_COMPLEX,1.0,Scalar(120,12,200),1,8);//注意：CV_FONT_HERSHEY_COMPLEX是字体，1.0是字体大小
//随机图形
RandomLineDemo();
namedWindow(drawdemo_win,CV_WINDOW_AUTOSIZE);
imshow(drawdemo_win,bgImage);
waitKey(0);
return 0;
}
void MyLines(){
Point p1 = Point(20,30);
Point p2;
p2.x = 300;
p2.y = 300;
Scalar color = Scalar(0,0,255);
line(bgImage,p1,p2,color,1,LINE_8);
}
void MyRectangle(){
Rect rect = Rect(200,100,300,300);
Scalar color = Scalar(255,0,0);
rectangle(bgImage,rect,color,2,LINE_8);
//rectangle(cv::Mat &img,cv::Rectt rec,const cv::Scalar &color,int thickness = 1,int lineType = 8,int shift = 0)
//thickness 线宽
}
void MyEllipse(){
ellipse (bgImage,Point(bgImage.cols/2,bgImage.rows/2),Size(bgImage.cols/4,bgImage.rows/8),90,0,360,Scalar(0,255,0),2,LINE_8);//注意：90是旋转角度
}
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 MyPolygen(){
Scalar color = Scalar(255,0,255);
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};
fillPoly(bgImage,ppts,npt,1,color,LINE_8);
}
void RandomLineDemo(){
RNG rng(12345);
Mat bg = Mat::zeros(bgImage.size(),bgImage.type());
namedWindow("Line Demo",CV_WINDOW_AUTOSIZE);
Point pt1;
Point pt2;
for(int i = 0; i < 10000; 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(200,rng.uniform(0,255),rng.uniform(0,255));
if(WaitKey(50)>0){
break;
}
line(bgImage,pt1,pt2,color,1,8);
imshow("Line Demo",bg);
}
}
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)
来源：CSDN
作者：Qsouler
链接：https://blog.csdn.net/Qsouler/article/details/104216218