問題描述

我有一個(gè)功能正常的繪圖應(yīng)用程序，用于對(duì)圖像進(jìn)行一些分割.為此，我有兩層，原始圖像和我正在繪制的圖像層.

I have a functioning drawing application for some segmentation on images. For this I have two layers, the original image and the image layer I am drawing on.

我現(xiàn)在想實(shí)現(xiàn)一種擦除方法.我已經(jīng)實(shí)現(xiàn)了撤消功能，但我也希望用戶能夠選擇畫筆顏色"以便能夠擦除特定部分，例如油漆中的橡皮擦.我認(rèn)為這可以通過使用不透明的顏色進(jìn)行繪制來實(shí)現(xiàn)，但這只會(huì)導(dǎo)致不繪制線條.

I now want to implement a method for erasing. I have implemented undo functionality, but I would also like the user to be able to select a brush "color" as to be able to erase specific parts, like the eraser in paint. I thought this would be possible by drawing with a color with opacity, but that just results in no line being drawn.

因此，我的目標(biāo)是畫一條線，去除圖像層中的像素值，以便我可以看到底層圖像

The goal for me is therefore to draw a line, that removes the pixel values in the image layer, such that I can see the underlying image

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()

如何擦除像素子集?

在這個(gè)例子中，應(yīng)該為 changeColour 函數(shù)中的 self.brushColor 賦予什么顏色?

How to erase a subset of pixels?

As in this example what color should be given to self.brushColor in the changeColour function?

白色不是解決方案，因?yàn)閷?shí)際上底部的圖像是一個(gè)復(fù)雜的圖像，因此我想在擦除時(shí)再次使頂層透視".

The colour white is not the solution, because in reality the image at the bottom is a complex image, I therefore want to make the toplayer "see-through" again, when erasing.

推薦答案

你必須改變 compositionMode 到 QPainter::CompositionMode_Clear 并用 eraseRect().

You have to change the compositionMode to QPainter::CompositionMode_Clear and erase with eraseRect().

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())

這篇關(guān)于在畫布上擦筆的文章就介紹到這了，希望我們推薦的答案對(duì)大家有所幫助，也希望大家多多支持html5模板網(wǎng)！