QPainter to draw custom-size image

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QPainter to draw pictures using drawPixmap interfaces, qt offers two rendering mode, the interface is as follows:

1. First, the incoming draw points, left corner of the picture is the anchor point, how to draw big picture, if you need to modify the image size, the scale can be QPixmap method for image to zoom, but the scale method use, picture resolution will be reduced.

2. The second, pass a rectangle, this method of drawing out of the picture size is set by the size of the rectangle, the image will be scaled to the size of QPixmap QRect within the scope of re-rendering, picture resolution will not change much.

The second approach is recommended to draw