python - `QImage` constructor has unknown keyword `data`

Question

Suppose I am taking an image from the webcam using opencv.

_, img = self.cap.read()  # numpy.ndarray (480, 640, 3)

Then I create a QImage qimg using img:

qimg = QImage(
    data=img,
    width=img.shape[1],
    height=img.shape[0],
    bytesPerLine=img.strides[0],
    format=QImage.Format_Indexed8)

But it gives an error saying that:

TypeError: 'data' is an unknown keyword argument

But said in this documentation, the constructor should have an argument named data.

I am using anaconda environment to run this project.

opencv version = 3.1.4

pyqt version = 5.9.2

numpy version = 1.15.0

Answer 1

What they are indicating is that the data is required as a parameter, not that the keyword is called data, the following method makes the conversion of a numpy/opencv image to QImage:

from PyQt5.QtGui import QImage, qRgb
import numpy as np
import cv2

gray_color_table = [qRgb(i, i, i) for i in range(256)]

def NumpyToQImage(im):
    qim = QImage()
    if im is None:
        return qim
    if im.dtype == np.uint8:
        if len(im.shape) == 2:
            qim = QImage(im.data, im.shape[1], im.shape[0], im.strides[0], QImage.Format_Indexed8)
            qim.setColorTable(gray_color_table)
        elif len(im.shape) == 3:
            if im.shape[2] == 3:
                qim = QImage(im.data, im.shape[1], im.shape[0], im.strides[0], QImage.Format_RGB888)
            elif im.shape[2] == 4:
                qim = QImage(im.data, im.shape[1], im.shape[0], im.strides[0], QImage.Format_ARGB32)
    return qim

img = cv2.imread('/path/of/image')
qimg = NumpyToQImage(img)
assert(not qimg.isNull())

or you can use the qimage2ndarray library

When using the indexes to crop the image is only modifying the shape but not the data, the solution is to make a copy

img = cv2.imread('/path/of/image')
img = np.copy(img[200:500, 300:500, :]) # copy image
qimg = NumpyToQImage(img)
assert(not qimg.isNull())