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.
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.
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
MVP of drawing
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()
How to erase a subset of pixels?
As in this example what color should be given to self.brushColor
in the changeColour
function?
Info
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.