Python 在画布上擦笔

我有一个功能强大的绘图应用程序，可以对图像进行分割。为此，我有两个层，原始图像和我正在绘制的图像层

现在我想实现一种擦除方法。我已经实现了撤销功能，但我也希望用户能够选择一个笔刷“颜色”，以便能够擦除特定的部分，如油漆中的橡皮擦。我认为这将是可能的绘制与不透明的颜色，但这只是在没有画线的结果

因此，我的目标是画一条线，删除图像层中的像素值，以便我可以看到底层图像

绘图的MVP 如何删除像素子集？ 如本例所示，在

changeColour

功能中，应为

self.brushColor

指定什么颜色

信息 白色不是解决方案，因为实际上底部的图像是一个复杂的图像，因此我想在擦除时使顶层再次“透明”。

您必须更改为

QPainter:：CompositionMode\u清除

并使用擦除

---

什么叫复杂图像？@eyllanesc只是许多不同的颜色，所以你不能对底层图像做任何假设。这只是为了强调一点，即更改只应发生在顶层。一个问题，然后我将其标记为已接受：）我可以轻松更改正方形的大小，但尽管更改了清除大小，擦除区域仍然很小？@JTIM我觉得奇怪，矩形的面积等于擦除区域。你可以指出你是如何实现它的，我认为你做得不对，我没有你指出的问题，啊，忘了考虑缩放的比例因子。谢谢；）@JTIM你看，没有a很难帮助：-）呵呵，是的，但是整个项目太大了，缩放很难工作（至少对我来说；）。但您的代码让我看到它应该可以工作，然后就很清楚了；）Thx，祝你有愉快的一天

from PyQt5.QtWidgets import QApplication, QMainWindow, QMenuBar, QMenu, QAction
from PyQt5.QtGui import QIcon, QImage, QPainter, QPen
from PyQt5.QtCore import Qt, QPoint
from PyQt5.QtGui import QColor
import sys

class Window(QMainWindow):
    def __init__(self):
        super().__init__()

        top = 400
        left = 400
        width = 800
        height = 600

        self.setWindowTitle("MyPainter")
        self.setGeometry(top, left, width, height)

        self.image = QImage(self.size(), QImage.Format_ARGB32)
        self.image.fill(Qt.white)
        self.imageDraw = QImage(self.size(), QImage.Format_ARGB32)
        self.imageDraw.fill(Qt.transparent)

        self.drawing = False
        self.brushSize = 2
        self.brushColor = Qt.black
        self.lastPoint = QPoint()

        self.change = False
        mainMenu = self.menuBar()
        changeColour = mainMenu.addMenu("changeColour")
        changeColourAction = QAction("change",self)
        changeColour.addAction(changeColourAction)
        changeColourAction.triggered.connect(self.changeColour)

    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.imageDraw)
            painter.setPen(QPen(self.brushColor, self.brushSize,     Qt.SolidLine, Qt.RoundCap, Qt.RoundJoin))
            painter.drawLine(self.lastPoint, event.pos())
            self.lastPoint = event.pos()
            self.update()

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

    def paintEvent(self, event):
        canvasPainter = QPainter(self)
        canvasPainter.drawImage(self.rect(), self.image, self.image.rect())
        canvasPainter.drawImage(self.rect(), self.imageDraw, self.imageDraw.rect())

    def changeColour(self):
        if not self.change:
            # erase
            self.brushColor = QColor(255,255,255,0)
        else:
            self.brushColor = Qt.black
        self.change = not self.change

if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    app.exec()

from PyQt5 import QtCore, QtGui, QtWidgets

class Window(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        top, left, width, height = 400, 400, 800, 600
        self.setWindowTitle("MyPainter")
        self.setGeometry(top, left, width, height)

        self.image = QtGui.QImage(self.size(), QtGui.QImage.Format_ARGB32)
        self.image.fill(QtCore.Qt.white)
        self.imageDraw = QtGui.QImage(self.size(), QtGui.QImage.Format_ARGB32)
        self.imageDraw.fill(QtCore.Qt.transparent)

        self.drawing = False
        self.brushSize = 2
        self._clear_size = 20
        self.brushColor = QtGui.QColor(QtCore.Qt.black)
        self.lastPoint = QtCore.QPoint()

        self.change = False
        mainMenu = self.menuBar()
        changeColour = mainMenu.addMenu("changeColour")
        changeColourAction = QtWidgets.QAction("change", self)
        changeColour.addAction(changeColourAction)
        changeColourAction.triggered.connect(self.changeColour)

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

    def mouseMoveEvent(self, event):
        if event.buttons() and QtCore.Qt.LeftButton and self.drawing:
            painter = QtGui.QPainter(self.imageDraw)
            painter.setPen(QtGui.QPen(self.brushColor, self.brushSize, QtCore.Qt.SolidLine, QtCore.Qt.RoundCap, QtCore.Qt.RoundJoin))
            if self.change:
                r = QtCore.QRect(QtCore.QPoint(), self._clear_size*QtCore.QSize())
                r.moveCenter(event.pos())
                painter.save()
                painter.setCompositionMode(QtGui.QPainter.CompositionMode_Clear)
                painter.eraseRect(r)
                painter.restore()
            else:
                painter.drawLine(self.lastPoint, event.pos())
            painter.end()
            self.lastPoint = event.pos()
            self.update()

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

    def paintEvent(self, event):
        canvasPainter = QtGui.QPainter(self)
        canvasPainter.drawImage(self.rect(), self.image, self.image.rect())
        canvasPainter.drawImage(self.rect(), self.imageDraw, self.imageDraw.rect())

    def changeColour(self):
        self.change = not self.change
        if self.change:
            pixmap = QtGui.QPixmap(QtCore.QSize(1, 1)*self._clear_size)
            pixmap.fill(QtCore.Qt.transparent)
            painter = QtGui.QPainter(pixmap)
            painter.setPen(QtGui.QPen(QtCore.Qt.black, 2))
            painter.drawRect(pixmap.rect())
            painter.end()
            cursor = QtGui.QCursor(pixmap)
            QtWidgets.QApplication.setOverrideCursor(cursor)
        else:
            QtWidgets.QApplication.restoreOverrideCursor()

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec())