使用 mouseDown C++/CLI 在图像上创建矩形

Question

我在调试这个程序时遇到困难。我正在尝试模仿微软桌面上可以拖动到矩形中的功能。
我们希望做到：
1. 为了开始绘制矩形，请按下鼠标。
2. 通过向下拖动鼠标，您可以创建矩形的形状和大小。
3. 松开鼠标即可结束矩形的绘制
4.我们希望能够跟踪起点和终点。


到目前为止我们已经

 private: System::Void pictureBox1_Paint(System::Object^  sender, System::Windows::Forms::PaintEventArgs^  e) {

        // e->Graphics;
        //put pen where it belongs..
        Pen^ blackPen = gcnew Pen( Color::Black,3.0f );

        if(drawing)
        {
        e->Graphics->DrawRectangle( blackPen, *getRect(ROIlocation1->X, ROIlocation1->Y, ROIlocation2->X, ROIlocation2->Y ));
        }   
        //pictureBox1->Invalidate();
     }
 private: System::Void pictureBox1_MouseDown(System::Object^  sender, System::Windows::Forms::MouseEventArgs^  e) {

        currentPos = startPos = e->Location;
        ROIlocation1 = startPos;
        drawing = true;
        pictureBox1->Invalidate();
     }

 private: System::Void pictureBox1_MouseUp(System::Object^  sender, System::Windows::Forms::MouseEventArgs^  e) {


         //NEW
         if (drawing){
             drawing = false;
             //getRect(startPos->X, startPos->Y, currentPos->X, currentPos->Y);
             pictureBox1->Invalidate();
        }

     }

private: System::Void pictureBox1_MouseMove(System::Object^  sender, System::Windows::Forms::MouseEventArgs^  e) {


         //NEW
         currentPos=e->Location;
         ROIlocation2=currentPos;
         if(drawing) pictureBox1->Invalidate();



     }

这是 getRect 函数：

System::Drawing::Rectangle^ getRect(int xOne, int yOne, int xTwo, int yTwo){
// ms drawRect(x,y,w,h) wants the upper left corner of the rectangle, and the width and height.
// we are given two sets of coordinates. the user can draw the rectangle in four ways,
// not necessarily starting with the upper right hand corner of the rectangle. 
// this function will return a rectangle with the appropriate attributes 
// that the user expects.

int ulpX = std::min(xOne, xTwo); // upper left point x
int ulpY = std::max(yOne, yTwo); //upper left point y
int h = abs(xOne - xTwo); //height
int w = abs(yOne - yTwo); //width


return gcnew System::Drawing::Rectangle(ulpX, ulpY, w, h);

 }

我们遇到的问题是矩形不断移动，就好像它没有将第一次单击图像的位置作为其位置一样。

Answer 1

找出问题所在：

int w = abs(xOne - xTwo); //width
int h = abs(yOne - yTwo); //height