PyQt5 – 如何从矩形图像中获取裁剪的方形图像？

在本文中，我们将看到如何从任何宽度和高度的矩形图像中仅显示裁剪的方形图像，即

In order to do so we have to do the following steps :

1. Load the image
2. Crop image to make it square
3. Mask it and make perfect square from it using Painter
4. Convert it back to pixmap image

编程需要懂一点英语

代码 -

对于下面的原始图像是代码：

# importing libraries
from PyQt5.QtCore import * 
from PyQt5.QtGui import * 
from PyQt5.QtWidgets import *
  
# function to alter image
def mask_image(imgdata, imgtype ='png', size = 64):
  
    # Load image
    image = QImage.fromData(imgdata, imgtype)
  
    # convert image to 32-bit ARGB (adds an alpha 
    # channel ie transparency factor):
    image.convertToFormat(QImage.Format_ARGB32)
  
    # Crop image to a square:
    imgsize = min(image.width(), image.height())
    rect = QRect(
        (image.width() - imgsize) / 2,
        (image.height() - imgsize) / 2,
        imgsize,
        imgsize,
    )
    image = image.copy(rect)
  
    # Create the output image with the 
    # same dimensions and an alpha channel
    # and make it completely transparent:
    out_img = QImage(imgsize, imgsize, QImage.Format_ARGB32)
    out_img.fill(Qt.transparent)
  
    # Create a texture brush and paint a circle
    # with the original image onto
    # the output image:
    brush = QBrush(image)
  
    # Paint the output image
    painter = QPainter(out_img)
    painter.setBrush(brush)
  
    # Don't draw an outline
    painter.setPen(Qt.NoPen)
  
    # drawing square
    painter.drawRect(0, 0, imgsize, imgsize)
  
    # closing painter event
    painter.end()
  
    # Convert the image to a pixmap and rescale it.
    pr = QWindow().devicePixelRatio()
    pm = QPixmap.fromImage(out_img)
    pm.setDevicePixelRatio(pr)
    size *= pr
    pm = pm.scaled(size, size, Qt.KeepAspectRatio, 
                               Qt.SmoothTransformation)
  
    # return back the pixmap data
    return pm
  
  
class Window(QWidget):
  
    """Simple window that shows our masked image and text label."""
    def __init__(self):
        super().__init__()
  
        # setting up the geometry
        self.setGeometry(100, 100, 600, 400)
  
        # image path
        imgpath = "image.png"
  
        # loading image
        imgdata = open(imgpath, 'rb').read()
  
        # calling the function
        pixmap = mask_image(imgdata)
  
        # creating label
        self.ilabel = QLabel(self)
  
        # putting image on label
        self.ilabel.setPixmap(pixmap)
  
        # moving the label
        self.ilabel.move(240, 180)
  
        # another label to put text
        self.tlabel = QLabel('This is croped image', self)
        self.tlabel.move(200, 250)
  
  
  
# main function
if __name__ == '__main__':
    import sys
    from PyQt5.QtWidgets import QApplication
  
    # app created
    app = QApplication(sys.argv)
    w = Window()
    w.show()
  
    # begin the app
    sys.exit(app.exec_())

输出：