PyQT different image autoscaling modes

Question

Let's say we have a QLabel with QPixmap

label = QLabel
Pixmap = QPixmap('filepath')
label.setPixmap(Pixmap)

I already mentioned that by using

label.setScaledContents(True) 

We can force image to be autoscaled to label size (And widget's one if label autoscaled to it) Without using it, image gona be displayed in it's full size, not depending on window or label's one. Now i want it to be autoscaled to label's size, but keeping it's aspect ratio.

Answer 1

Try it:

import sys
from PyQt5.QtWidgets import *
from PyQt5.QtCore    import *
from PyQt5.QtGui     import * 

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        centralWidget = QWidget()
        self.setCentralWidget(centralWidget)  

        self.label  = QLabel() 
        self.pixmap = QPixmap("head.jpg")
        self.label.setPixmap(self.pixmap.scaled(self.label.size(),
                Qt.KeepAspectRatio, Qt.SmoothTransformation))

        self.label.setSizePolicy(QSizePolicy.Expanding,
                QSizePolicy.Expanding)
        self.label.setAlignment(Qt.AlignCenter)
        self.label.setMinimumSize(100, 100) 

        layout = QGridLayout(centralWidget)    
        layout.addWidget(self.label)        

    def resizeEvent(self, event):
        scaledSize = self.label.size()                       
        scaledSize.scale(self.label.size(), Qt.KeepAspectRatio)
        if not self.label.pixmap() or scaledSize != self.label.pixmap().size():
            self.updateLabel()    

    def updateLabel(self):
        self.label.setPixmap(self.pixmap.scaled(        
                self.label.size(), Qt.KeepAspectRatio,
                Qt.SmoothTransformation))

if __name__ == "__main__":
    import sys
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())