使用 QPainter 叠加两个具有 alpha 值的像素图

Question

我正在尝试叠加 2 个像素图并将它们转换为 QGraphics 场景中的单个像素图。两个像素图在某些位置都是透明的。我想使用列出的 'SourceOver' 混合类型组合贴图 here: I have a simple toy example below to illustrate my issue where I have created two dummy transparent pixmaps, one green and one blue. In reality, these maps are loaded from images and painted over, but this example reproduces the problem. Based on this How to add an image on the top of another image?，我尝试的方法（注释掉 4 行）是用其中一个像素图创建一个 QPainter，然后绘制另一个像素图在它上面，但是会使程序崩溃。有想法该怎么解决这个吗？我最终希望能够保存组合的像素图。

import sys
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtGui import QPixmap, QPainter, QPen, QBrush, QPainterPath
from PyQt5.QtCore import (QLineF, QPointF, QRectF, Qt)

class Viewer(QtWidgets.QGraphicsView):
    def __init__(self, parent):
        super(Viewer, self).__init__(parent)
        self._scene = QtWidgets.QGraphicsScene(self)
        self.photo = QtWidgets.QGraphicsPixmapItem()
        self.label = QtWidgets.QGraphicsPixmapItem()
        self._scene.addItem(self.photo)
        self._scene.addItem(self.label)
        self.setScene(self._scene)        

    def overlayMaps(self):
        blue = QtGui.QPixmap(600, 600) 
        blue.fill(QtGui.QColor(0,0,255,0))
        p = QPainter(blue)
        self.pen = QPen()
        self.pen.setColor(QtGui.QColor(0,0,255,255))
        self.pen.setWidth(10)
        p.setPen(self.pen)
        p.drawLine(0,0,600,600)


        green = QtGui.QPixmap(600, 600)
        green.fill(QtGui.QColor(0,255,0,0))            
        p = QPainter(green)
        self.pen = QPen()
        self.pen.setColor(QtGui.QColor(0,255,0,255))
        self.pen.setWidth(10)
        p.setPen(self.pen)
        p.drawLine(600,0,0,600)

        self.photo.setPixmap(blue)
        self.label.setPixmap(green) 

        resultPixmap = QtGui.QPixmap(self.photo.pixmap().width(), self.photo.pixmap().height())
#        resultPainter = QtGui.QPainter(resultPixmap)
#        resultPainter.setCompositionMode(QtGui.QPainter.CompositionMode_SourceOver)
#        resultPainter.drawPixmap(300,300, self.photo.pixmap()) 
#        resultPainter.drawPixmap(300,300, self.label.pixmap()) 


    def saveOverlayMap(self):
        pass          

class Window(QtWidgets.QWidget):
    def __init__(self):
        super(Window, self).__init__()
        self.viewer = Viewer(self)
        self.viewer.overlayMaps()

if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    window = Window()
    window.setGeometry(500, 300, 600, 600)
    window.show()
    sys.exit(app.exec_())

Answer 1

我已经实现了一个功能，可以根据模式执行加入操作，为了更好地欣赏我已经移动了项目。

import sys
from PyQt5 import QtCore, QtGui, QtWidgets

def join_pixmap(p1, p2, mode=QtGui.QPainter.CompositionMode_SourceOver):
    s = p1.size().expandedTo(p2.size())
    result =  QtGui.QPixmap(s)
    result.fill(QtCore.Qt.transparent)
    painter = QtGui.QPainter(result)
    painter.setRenderHint(QtGui.QPainter.Antialiasing)
    painter.drawPixmap(QtCore.QPoint(), p1)
    painter.setCompositionMode(mode)
    painter.drawPixmap(result.rect(), p2, p2.rect())
    painter.end()
    return result

class Viewer(QtWidgets.QGraphicsView):
    def __init__(self, parent=None):
        super(Viewer, self).__init__(parent)
        self._scene = QtWidgets.QGraphicsScene(self)
        self.setScene(self._scene)  

        blue = QtGui.QPixmap(100, 100) 
        blue.fill(QtCore.Qt.transparent)
        p = QtGui.QPainter(blue)
        pen = QtGui.QPen(QtGui.QBrush(QtGui.QColor(0,0,255)), 10)
        p.setPen(pen)
        p.drawLine(0, 0, 100, 100)
        p.end()
        self.photo = self._scene.addPixmap(blue)

        green = QtGui.QPixmap(100, 100)
        green.fill(QtCore.Qt.transparent)            
        p = QtGui.QPainter(green)
        pen = QtGui.QPen(QtGui.QBrush(QtGui.QColor(0, 255, 0, 255)), 10)
        p.setPen(pen)
        p.drawLine(100, 0, 0, 100)
        p.end()
        self.label = self._scene.addPixmap(green) 
        self.label.setPos(200, 0)     

        self.overlayMaps()

    def overlayMaps(self):
        p1 = QtGui.QPixmap(self.photo.pixmap())
        p2 = QtGui.QPixmap(self.label.pixmap())

        result_pixmap = join_pixmap(self.photo.pixmap(), self.label.pixmap())
        self.result_item = self._scene.addPixmap(result_pixmap)
        self.result_item.setPos(100, 200)

        result_pixmap.save("result_pixmap.png")

if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    window = Viewer()
    window.resize(640, 480)
    window.show()
    sys.exit(app.exec_())

result_pixmap.png

使用 QPainter 叠加两个具有 alpha 值的像素图

Overlay two pixmaps with alpha value using QPainter

python

pyqt

qpixmap

qpainter

pyqt5