opencv display big picture

This blog post implements the function of opencv to display a large image. When the image is too large, the content of the image cannot be fully displayed in a specific window.

At this time, as long as you drag any point of the visible part of the image with the mouse, you can expand and display the image content.

Gossip less, paste the code directly:

// MainDemo.cpp : Defines the entry point for the console application.
#include "stdio.h"
#include "highgui.h"
#include "cv.h"
#include <iostream>
using namespace std;


#define default_width 720
#define default_height 480 //图片的宽高超过此界限时认为是大图片

const char * filename= "beijing.bmp"; 

CvPoint first = cvPoint(0,0);
CvPoint  last = cvPoint(0,0);//鼠标按下和抬起时的点

CvRect rect;//显示的图像在原图中的区域

int src_x = 0;
int src_y = 0;	//ROI左上角点

IplImage * img;
int img_width,img_height;	//读入的图片的宽高

int window_height ;
int window_width  ;		//窗口的宽高
IplImage * dst_image;	//显示的图片


void on_mouse(int event ,int x, int y,int flags, void* param)
{
	switch(event)
	{
		case CV_EVENT_LBUTTONDOWN:
			{
				first.x = x;
				first.y = y;
			}
			break;
		case CV_EVENT_LBUTTONUP:
			{
				last.x = x;
				last.y = y;

				src_x -= last.x - first.x;
				src_y -= last.y - first.y;

				if(src_x < 0)src_x = 0;
				else if(src_x > img_width - window_width)src_x = img_width - window_width;
				else ;
				if(src_y < 0 ) src_y = 0;
				else if(src_y > img_height - window_height)src_y = img_height - window_height;
				else;
				cout<<"左上角点："<<endl;
				cout<<"x:"<<src_x<<endl;
				cout<<"y:"<<src_y<<endl;
				rect = cvRect(src_x, src_y,window_width , window_height);

				cvSetImageROI(img , rect);
				//将矩形区内的图像复制出来
				cvCopy(img,dst_image);
				cvResetImageROI(img);
				cvShowImage("image", dst_image);
			}
			break;
		default: break;
	}
}

int main()
{
	img = cvLoadImage(filename,1);
	img_width = img->width;
	img_height = img->height;
	//如果图片没有大于默认大小，则可以直接调用opencv的显示函数
	if(img_height <= default_height && img_width <= default_width)
	{
		cvNamedWindow("image",CV_WINDOW_AUTOSIZE);
		cvShowImage("image",img);
		cvWaitKey(0);
		cvReleaseImage(&img);
		cvDestroyAllWindows();
		return 0;
	}
	//如果存在长或宽大于默认值，则需要添加滚动条
	//如果不添加滚动条，直接拖动也可以实现
	//记录鼠标的拖动
	else
	{
		window_height = default_height;
		window_width  = default_width;

		//假如列或者宽小于默认值，则需要调整

		if(img_height < default_height){window_height = img_height;}
		if(img_width  < default_width){ window_width  = img_width; }

		//设置ROI，将ROI内的区域拷贝出来
	     dst_image = cvCreateImage(cvSize(window_width,window_height),img->depth,img->nChannels);
	     rect = cvRect(src_x, src_y,window_width,window_height);

		cvSetImageROI(img , rect);
		//将矩形区内的图像复制出来
		cvCopy(img,dst_image);
		cvResetImageROI(img);
		cvNamedWindow("image",1);
		cvResizeWindow("image",window_width,window_height);
		cvShowImage("image", dst_image);

		//下面开始处理鼠标事件
		//鼠标buttondown和buttonup分别记下其位置，然后由此可以计算出移动的距离
		cvSetMouseCallback("image",on_mouse ,0);
		cvWaitKey(0);
		cvReleaseImage(&img);
		cvDestroyAllWindows();
	}
	return 0 ;
}

The display results are as follows:

Display the image for the first time:

The result displayed after dragging the mouse:

Source code download address: http://download.csdn.net/detail/beijingmake209/7342749