Drawing event: if drawing on the window, it must be placed in the drawing event
The function used to draw the background image: Qpainter object.drawPixmap
The function used to draw the rectangle: Qpainter object.drawRect, of course, the painter must be handed over to the painter before this: Qpainter object.setpen(pen)
If you want to implement a function, you need to refresh the window and let the window be redrawn, just execute the update() statement in the slot function. It is equivalent to calling paintEvent() indirectly.
QPixmap is the parent class of QBitmap. The latter has only two colors, and the former is a color image. The above and below are different methods, and both can be used.
Commonly used drawing equipment (drawing board): QPixmap (optimized for the screen, and platform-related, can not modify the picture, generally used for display), QImage (related to the platform, you can modify the picture, you can draw in the thread) , QPicture (save the state of the drawing-binary file), the usage of the three of them is basically similar,If you use them as a drawing device, you can put it in the constructor, and you don’t need to put it in the drawing event.。
Conversion between QPixmap and QImage: pixmap.toImage() or Pixmap::fromImage(image) function can realize the conversion between the two.
