opencv实现图片裁剪和缩放

1. 格式转换 yuv2rgb

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

using namespace std;
using namespace cv;

#define IMAGE_LEN 622080
#define IMAGE_WIDTH 720
#define IMAGE_HEIGHT 576

int main()
{
        ifstream fd_yuv("in.yuv");
        //yuv Mat mem
        cv::Mat yuv_img(IMAGE_HEIGHT*1.5, IMAGE_WIDTH, CV_8UC1);

        //read to Mat
        fd_yuv.read((char *)yuv_img.data, IMAGE_LEN);

        //cv jpg 2 Mat
        cv::Mat jpg_img;
        cv::cvtColor(yuv_img, jpg_img, CV_YUV2RGB_NV12);
        imwrite("out.jpg", jpg_img);

        return 0;
}

2. opencv crop image

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

using namespace std;
using namespace cv;

int main()
{
	// Read image
	Mat img = imread("test.jpg"); 
	cout << "Width : " << img.size().width << endl;
	cout << "Height: " << img.size().height << endl;
	// Crop image  //起点坐标和终点坐标的矩形
    //img(Range(start_row, end_row), Range(start_col, end_col))
	Mat crop_image = img(Range(80,280), Range(150,330));

	//Save Image
	imwrite("image.jpg", crop_image);
	return 0;
}

3. opencv resize image

/*
src:输入图像
dst:输出图片
dsize：输出图像尺寸，0 则为 dsize=Size(round(fxsrc.cols),round(fysrc,rows))结果
fx:水平轴缩放系数，默认为0
fy:y轴缩放系数，默认为0 
interpolation：插值方法，INTER_LINEAR线性插值，INTER_NN - 最近邻插值,  INTER_LINEAR - 双线性插值..
void resize( InputArray src, 
             OutputArray dst, 
             Size dsize, 
             double fx = 0, 
             double fy = 0,
             int interpolation = INTER_LINEAR );
*/
#include<iostream>
#include<opencv2/opencv.hpp>
#include<opencv2/imgproc/imgproc.hpp>

int main()
{
    
    cv::Mat src = cv::imread("image.jpg", cv::IMREAD_UNCHANGED); 

    float scale = 0.8; //长缩放系数
    float scaleH = 0.8;  //高缩放系数
   
    int width = int(src.cols * scale)
    int height= int(src.rows * scale)
    cv::Mat dst;
   
    /* 缩放图像函数
       src：原图像
       dst：目标图像
       参数3：目标图像的大小
    */
    resize(src, dst, cv::Size(width, height));  

    //cv::imshow("src", src);
    //cv::imshow("dst", dst);
    //cv::waitKey();
        
}