我正在将OpenCV ans SDL2库用于C ++应用程序。
Opencv用于从网络摄像头捕获帧，然后将该帧转换为显示在SDL窗口中。 SDL用于捕获鼠标的输入。
在SDL窗口中的每一次单击，都会在网络摄像头框架上的单击位置绘制一个圆圈。
问题如下：在运行应用程序时手动调整窗口大小（从OS而不是从代码），将正确绘制已经绘制的点，但是如果我单击鼠标左键以在其中绘制另一个点调整大小后的窗口，该点将完全绘制在窗口范围之外。
这是主要功能：
#ifndef __OPENCV__
#define __OPENCV__
#include "opencv2/opencv.hpp"
#endif
#include <iostream>
#include <unistd.h>
#include <vector>
#include <SDL.h>
#include <SDL_events.h>
using namespace cv;
using namespace std;
int mouseCallback(SDL_MouseButtonEvent ev, Mat frame);
int main(int argc, char* argv[])
{
/* Initialise SDL */
if( SDL_Init( SDL_INIT_VIDEO ) < 0)
{
fprintf( stderr, "Could not initialise SDL: %s\n", SDL_GetError() );
exit( -1 );
}
const String sourceReference = argv[1];
int camNum;
string sensorName;
try
{
camNum = stoi(sourceReference); // throws std::length_error
}
catch (const std::exception& e)// reference to the base of a polymorphic object
{
std::cout<<"Exception: " << e.what()<<endl; // information from length_error printed
return -1;
}
cout<<"camera initializing\n";
VideoSettings cam(camNum + CAP_V4L);
cout<<"camera initialized\n";
/* or
VideoCapture captUndTst;
captUndTst.open(sourceCompareWith);*/
cout<<"Ch3ck c4m3ra is 0p3n3d\n";
if ( !cam.isOpened())
{
cout << "Could not open reference " << sourceReference << endl;
return -1;
}
Mat frame;
cam>>frame;
SDL_Window* win = SDL_CreateWindow("Camera", 100, 100, frame.cols, frame.rows,
SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE);
SDL_SetWindowTitle(win, "Camera");
SDL_Renderer * renderer = SDL_CreateRenderer(win, -1, 0);
SDL_Event genericEvent;
SDL_Surface* frameSurface;
SDL_Texture* frameTexture;
while(cam.isOpened())
{
while( SDL_PollEvent(&genericEvent) )
{
switch( genericEvent.type )
{
case SDL_MOUSEBUTTONDOWN:
mouseCallback(genericEvent.button, frame);
break;
/* SDL_QUIT event (window close) */
case SDL_QUIT:
return 0;
break;
default:
break;
}
}
cam>>frame;
draw(frame_out);
//Convert to SDL_Surface
frameSurface = SDL_CreateRGBSurfaceFrom((void*)frame_out.data,
frame_out.size().width, frame_out.size().height,
24, frame_out.cols *3,
0xff0000, 0x00ff00, 0x0000ff, 0);
if(frameSurface == NULL)
{
SDL_Log("Couldn't convert Mat to Surface.");
return -2;
}
//Convert to SDL_Texture
frameTexture = SDL_CreateTextureFromSurface(renderer, frameSurface);
if(frameTexture == NULL)
{
SDL_Log("Couldn't convert Mat(converted to surface) to Texture."); //<- ERROR!!
return -1;
}
//imshow("Camera", frame_out);
SDL_RenderCopy(renderer, frameTexture, NULL, NULL);
SDL_RenderPresent(renderer);
/* A delay is needed to show (it actually wait for an input)*/
if(waitKey(delay)>delay){;}
}
SDL_DestroyTexture(frameTexture);
SDL_FreeSurface(frameSurface);
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(win);
return 0;
}
int mouseCallback(SDL_MouseButtonEvent ev, Mat frame)
{
if(ev.button == SDL_BUTTON_LEFT)
{
mouseLeft( ev.x, ev.y);
}
}
单击鼠标左键时，调用的函数是mouseCallback，它正在调用定义为的函数mouseLeft：
void mouseLeft(int x, int y)
{
Point pt;// = *((Point*)param);
pt.x = x;
pt.y = y;
pts.push_back(pt);
int ii=0;
int size = pts.size()-1;
while(ii<size && size>0)
{
if (euclideanDist(pt, pts.at(ii))<minDistance)
{
//cout<<pts->size()<<endl;
pts.erase (pts.begin()+ii);
// std::vector::end returns an iterator to the element following
//the last element of the container, not to the last element.
pts.erase(pts.end()-1);
size-=2;
}
else
{
;
}
ii++;
}
}
pts是Points的向量（它最初是类的成员，但在此示例中可以全局声明）。如果点击点与mouseLeft中的任何点足够接近，则调用pts时，会将其从向量中删除，否则将向后推新的点。
函数draw绘制存储在pts中的点以及连接这些点的线：
void draw(Mat &frame)
{
vector<Point> new_pts = pts; //avoid modifying the elements we are drawing
int sizeVector = pts.size();
if (sizeVector==1)
{
try
{
circle( frame, pts.at(0), radius, Scalar( 0, 0, 0), FILLED, 8,0);
}
catch (const out_of_range& e)
{
cout<<"Exception with command "<<endl;
cout<<"circle( frame, pts.at(0), radius, Scalar( 0, 0, 0), FILLED, 8,0)"<<endl;
}
}
else
{
int ii=0;
while(ii<(sizeVector-1) && sizeVector>0)
{
try
{
circle( frame, pts.at(ii), radius, Scalar( 0, 0, 0), FILLED, 8,0);
circle( frame, pts.at(ii+1), radius, Scalar( 0, 0, 0), FILLED, 8,0);
line(frame, pts.at(ii), pts.at(ii+1), Scalar( 0, 0, 0 ), 4, 8 );
}
catch (const out_of_range& e)
{
cout<<"Exception with commands: "<<endl;
cout<<"\tcircle( frame, pts.at(ii), radius, Scalar( 0, 0, 0), FILLED, 8,0)"<<endl;
cout<<"\tcircle( frame, pts.at(ii+1), radius, Scalar( 0, 0, 0), FILLED, 8,0);"<<endl;
cout<<"\tline(frame, pts.at(ii), pts.at(ii+1), Scalar( 0, 0, 0 ), 4, 8 );"<<endl;
}
if(pts.size()<=0) break;
ii++;
sizeVector= pts.size();
}
}
}
如果不是用SDL_Window* win = SDL_CreateWindow("Camera", 100, 100, frame.cols, frame.rows,
SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE);创建窗口，而是将其尺寸变倍，例如：SDL_Window* win = SDL_CreateWindow("Camera", 100, 100, 2*frame.cols, 2*frame.rows,
SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE);
请注意，发布的代码是对原始代码的重新改编，以使其保持简单易懂。如果有任何遗漏或不清楚的地方，请告诉我，以便我可以正确地编辑问题。
答案 0 :(得分：0)
问题如下：从SDL捕获的鼠标坐标基本上是正确的：当我将窗口放大时，坐标甚至可以具有较大的值。
问题在于，这些坐标是通过openCV绘制在从凸轮获取的帧上的，该帧始终具有相同的尺寸（基本上是凸轮的分辨率）。
在框架上绘制点之前，我必须在从凸轮获取的图像的尺寸内重新调整鼠标单击的坐标。
我找到了一个解决方案，方法是在定义窗口之后，将窗口的初始尺寸基本上存储在两个变量中：
SDL_Window* win = SDL_CreateWindow("Camera", 100, 100, frame.cols, frame.rows,
SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE);
int oldWidth = frame.cols, oldHeight= frame.rows;
int width, height;
float scaleX=1, scaleY=1;
然后在已经存在的切换案例中添加以下事件：
case SDL_WINDOWEVENT:
{
if (genericEvent.window.event==SDL_WINDOWEVENT_RESIZED)
{
//oldWidth = width;
//oldHeight = height;
SDL_GetWindowSize(win, &width, &height);
scaleX = (float)(width)/ float(oldWidth);
scaleY = (float)(height) / (float)(oldHeight);
}
break;
}
并将`mouseCallback修改为
int mouseCallback(SDL_MouseButtonEvent ev, float scaleX, float scaleY, Mat frame)
{
if(ev.button == SDL_BUTTON_LEFT)
{
cout<<scaleX<<" "<<scaleY<<endl;
int scaled_x = static_cast<int> ((float)(ev.x)/scaleX);
int scaled_y = static_cast<int> ((float)(ev.y)/ scaleY);
std::cout<<"scaled x: "<<scaled_x<<", scaled y: "<<scaled_y<<endl;
mouseLeft( scaled_x,scaled_y);
}
}