在 PyQt5 中跟踪鼠标的图像顶部绘图答案

【问题标题】：Drawing on top of image in PyQt5 tracing the mouse在 PyQt5 中跟踪鼠标的图像顶部绘图
【发布时间】：2018-12-30 16:47:48
【问题描述】：

我是 PyQt5 的新手。我试图在跟踪我的鼠标的加载图像线的顶部绘制，即按下鼠标将导致绘制鼠标移动到的任何位置，而鼠标仍被按下，并在我们释放鼠标时停止。

我看到了This answer，它很有帮助，但我正在尝试做一些更复杂的事情。

我想我搞砸了这些事件。

我写的（不起作用）：

import sys
from PyQt5.QtCore import Qt, QPoint
from PyQt5.QtWidgets import QMainWindow, QApplication, QLabel
from PyQt5.QtGui import QPixmap, QPainter, QPen


class Menu(QMainWindow):

    def __init__(self):
        super().__init__()
        self.drawing = False
        self.lastPoint = QPoint()
        self.image = QPixmap("picture.png")
        self.setGeometry(100, 100, 500, 300)
        self.resize(self.image.width(), self.image.height())
        self.label = QLabel(self)
        self.show()

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.drawPixmap(self.rect(), self.image)
        pen = QPen(Qt.red, 3)
        painter.setPen(pen)
        painter.drawLine(self.lastPoint, event.pos())

    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.drawing = True
            self.lastPoint = event.pos()

    def mouseMoveEvent(self, event):
        if event.buttons() and Qt.LeftButton and self.drawing:
            painter = QPainter(self.image)
            painter.setPen(QPen(Qt.red, 3, Qt.SolidLine))
            self.lastPoint = event.pos()
            self.update()

    def mouseReleaseEvent(self, event):
        if event.button == Qt.LeftButton:
            self.drawing = False


if __name__ == '__main__':
    app = QApplication(sys.argv)
    mainMenu = Menu()
    sys.exit(app.exec_())

【问题讨论】：

标签： python python-3.x pyqt pyqt5

【解决方案1】：

您想在mouseMoveEvent 中使用drawLine。当你移动鼠标时，它会调用mouseMoveEvent，它会从最后一个位置画一条线，然后它会自己调用paintEvent。

试试这个：

import sys
from PyQt5.QtCore import Qt, QPoint
from PyQt5.QtWidgets import QMainWindow, QApplication
from PyQt5.QtGui import QPixmap, QPainter, QPen


class Menu(QMainWindow):

    def __init__(self):
        super().__init__()
        self.drawing = False
        self.lastPoint = QPoint()
        self.image = QPixmap("picture.png")
        self.setGeometry(100, 100, 500, 300)
        self.resize(self.image.width(), self.image.height())
        self.show()

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.drawPixmap(self.rect(), self.image)

    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.drawing = True
            self.lastPoint = event.pos()

    def mouseMoveEvent(self, event):
        if event.buttons() and Qt.LeftButton and self.drawing:
            painter = QPainter(self.image)
            painter.setPen(QPen(Qt.red, 3, Qt.SolidLine))
            painter.drawLine(self.lastPoint, event.pos())
            self.lastPoint = event.pos()
            self.update()

    def mouseReleaseEvent(self, event):
        if event.button == Qt.LeftButton:
            self.drawing = False


if __name__ == '__main__':
    app = QApplication(sys.argv)
    mainMenu = Menu()
    sys.exit(app.exec_())

【讨论】：