在 QImage 之上创建一个透明网格

Question

我正在尝试构建一个具有网格的绘画应用程序，但我不想将网格包含在已保存的照片中。我试图在透明图像上绘图，但我得到的却是黑色背景！

完整代码如下：

import sys

from PyQt5 import QtGui, QtWidgets, QtCore
from PyQt5.QtCore import QPoint, Qt
from PyQt5.QtGui import QBrush, QGuiApplication, QImage, QPainter, QPen, QIcon, QColor
from PyQt5.QtWidgets import QApplication, QMainWindow, QVBoxLayout, QWidget, QTextEdit, QAction, QFileDialog,
    QGraphicsScene, QGraphicsProxyWidget, QGraphicsView

import pyautogui
import matplotlib.pyplot as plt




class Drawer(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)

        self._drawing = False
        self.last_point = QPoint()

        self.image_layer = QImage(self.size(), QImage.Format_RGB32)
        self.image_layer.fill(Qt.gray)

        self.brushSize = 2
        self.brushColor = Qt.black

        #paint = QPainter(self.image_layer)
        #paint.setCompositionMode(QtGui.QPainter.CompositionMode_Clear)

        # paint.drawLine(0,0,self.size().width(),0)
        # paint.drawLine(0,10,200,10)

        #paint.drawLine(0,0,0,200)
        #paint.drawLine(10,0,10,200)
        self.update()


    def mousePressEvent(self, event):
        self._drawing = True
        self.last_point = event.pos()

    def mouseMoveEvent(self, event):
        if self._drawing and event.buttons() & Qt.LeftButton:
            painter = QPainter(self.image_layer)
            painter.setPen(
                QPen(
                    self.brushColor,
                    self.brushSize,
                    Qt.SolidLine,
                    Qt.RoundCap,
                    Qt.RoundJoin,
                )
            )
            painter.drawLine(self.last_point, event.pos())
            self.last_point = event.pos()
            self.update()

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.drawImage(QPoint(), self.image_layer)
        painter.end()


    def resizeEvent(self, event):
        if (
                self.size().width() > self.image_layer.width()
                or self.size().height() > self.image_layer.height()
        ):
            qimg = QImage(
                max(self.size().width(), self.image_layer.width()),
                max(self.size().height(), self.image_layer.height()),
                QImage.Format_RGB32,
            )
            qimg.fill(Qt.gray)
            painter = QPainter(qimg)
            painter.drawImage(QPoint(), self.image_layer)
            painter.drawLine(0, 0, qimg.size().width(), 0)
            painter.drawLine(0, 10, qimg.size().width(), 10)
            painter.drawLine(0, 600, qimg.size().width(), 600)
            print(qimg.size().height())
            painter.end()
            self.image_layer = qimg
            self.update()

class Window(QMainWindow):
    def __init__(self, parent=None):
        super().__init__(parent)

        [x, y] = pyautogui.size()
        self.setGeometry(0, 0, x, y)

        self.drawer = Drawer()
        textbox = QTextEdit("Converted text will show here")

        central_widget = QWidget()
        self.setCentralWidget(central_widget)

        vlay = QVBoxLayout(central_widget)
        vlay.addWidget(textbox)
        vlay.addWidget(self.drawer, stretch=1)

        mainMenu = self.menuBar()
        fileMenu = mainMenu.addMenu("File")

        saveAction = QAction(QIcon("icons/save.png"), "Save", self)
        saveAction.setShortcut("Ctrl+S")
        fileMenu.addAction(saveAction)
        saveAction.triggered.connect(self.save)


    def save(self):
        filePath, _ = QFileDialog.getSaveFileName(self.drawer, "Save Image", "",
                                                  "PNG(*.png);;JPEG(*.jpg *.jpeg);;All Files(*.*) ")

        if filePath == "":
            return
        self.drawer.image_layer.save(filePath)

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

注意：只有两条模仿网格的线，我可以稍后再画，但现在我希望保存的图像不包括研磨线。

Answer 1

您应该在 paintEvent 中绘制网格，而不是连续绘制到图像上。

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.drawImage(QPoint(), self.image_layer)

        gridSize = 10
        x = y = 0
        width = self.width()
        height = self.height()
        while y <= height:
            # draw horizontal lines
            painter.drawLine(0, y, width, y)
            y += gridSize
        while x <= width:
            # draw vertical lines
            painter.drawLine(x, 0, x, height)
            x += gridSize

在 QImage 之上创建一个透明网格

create a transparent grid on top of QImage

python

pyqt

pyqt5