我有一個帶QLayout的QWidget,其上有一個QLabel.
我在標簽上設置了一個QPixmap.無論用戶點擊圖像,我想繪制一個點.我定義了mouseReleaseEvent(可以工作)和paintEvent(但是沒有繪制點).我已經閱讀了所有類似的問題,但沒有一個解決方案適合我.有幫助嗎？我的相關代碼：

class ImageScroller(QtWidgets.QWidget):

    def __init__(self, img):
        QtWidgets.QWidget.__init__(self)
        main_layout = QtWidgets.QVBoxLayout()
        self._image_label = QtWidgets.QLabel()
        self._set_image(img)
        main_layout.addWidget(self._image_label)
        main_layout.addStretch()
        self.setLayout(main_layout)

    def _set_image(self, img):
        img = qimage2ndarray.array2qimage(img)
        qimg = QtGui.QPixmap.fromImage(img)
        self._img_pixmap = QtGui.QPixmap(qimg)
        self._image_label.show()

    def paintEvent(self, paint_event):
        painter = QtGui.QPainter(self)
        painter.begin(self)
        painter.setPen(QtGui.QPen(QtCore.Qt.red))
        pen = QtGui.QPen()
        pen.setWidth(20)
        painter.setPen(pen)
        painter.setRenderHint(QtGui.QPainter.Antialiasing, True)
        painter.drawPoint(300,300)
        painter.drawLine(100, 100, 400, 400)
        for pos in self.chosen_points:
            painter.drawPoint(pos)
        painter.end()

    def mouseReleaseEvent(self, cursor_event):
        self.chosen_points.append(QtGui.QCursor().pos())
        self.update()

解決方法:

當您使用QtGui.QCursor.pos()獲取光標相對于屏幕的坐標時,但是當您想要繪制小部件時,您必須位于小部件的坐標中,因為小部件具有mapToGlobal()方法：

self.mapFromGlobal(QtGui.QCursor.pos())

但在這種情況下還有另一種解決方案,您必須使用返回具有pos()方法中信息的mouseReleaseEvent的事件：

cursor_event.pos()

另一個問題是您創(chuàng)建的標簽位于小部件上方,因此您看不到這些點,最簡單的方法是使用drawPixmap()方法直接繪制QPixmap.

完整代碼：

from PyQt5 import QtWidgets, QtGui, QtCore


class ImageScroller(QtWidgets.QWidget):
    def __init__(self):
        self.chosen_points = []
        QtWidgets.QWidget.__init__(self)
        self._image = QtGui.QPixmap("image.png")

    def paintEvent(self, paint_event):
        painter = QtGui.QPainter(self)
        painter.drawPixmap(self.rect(), self._image)
        pen = QtGui.QPen()
        pen.setWidth(20)
        painter.setPen(pen)
        painter.setRenderHint(QtGui.QPainter.Antialiasing, True)
        painter.drawPoint(300, 300)
        painter.drawLine(100, 100, 400, 400)
        for pos in self.chosen_points:
            painter.drawPoint(pos)

    def mouseReleaseEvent(self, cursor_event):
        self.chosen_points.append(cursor_event.pos())
        # self.chosen_points.append(self.mapFromGlobal(QtGui.QCursor.pos()))
        self.update()


if __name__ == '__main__':
    import sys

    app = QtWidgets.QApplication(sys.argv)
    w = ImageScroller()
    w.resize(640, 480)
    w.show()
    sys.exit(app.exec_())