Convert Python Opencv Image (numpy array) to PyQt QPixmap image

Question

I am trying to convert python opencv image to QPixmap.

I follow the instruction shows Page Link and my code is attached below

img = cv2.imread('test.png')[:,:,::1]/255. 
imgDown = cv2.pyrDown(img)
imgDown = np.float32(imgDown)        
cvRGBImg = cv2.cvtColor(imgDown, cv2.cv.CV_BGR2RGB)
qimg = QtGui.QImage(cvRGBImg.data,cvRGBImg.shape[1], cvRGBImg.shape[0], QtGui.QImage.Format_RGB888)
pixmap01 = QtGui.QPixmap.fromImage(qimg)
self.image01TopTxt = QtGui.QLabel('window',self)
self.imageLable01 = QtGui.QLabel(self)
self.imageLable01.setPixmap(pixmap01)

The code has no compile and runtime error but the conversion is wrong and I just get some noise image. I am not sure what the problem is. Could anyone help?

vwvw · Accepted Answer · 2019-11-27 19:59:56Z

49

Use this to convert cvImage to Qimage, here cvImage is the original image.

height, width, channel = cvImg.shape
bytesPerLine = 3 * width
qImg = QImage(cvImg.data, width, height, bytesPerLine, QImage.Format_RGB888)

and set this Qimage to Label.setPixmap parameter from Qimage. It works!!!

edited Nov 27, 2019 at 19:59

vwvw

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answered Mar 8, 2016 at 2:32

AdityaIntwala

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8 Comments

jfs Over a year ago

I had to create QPixmap explicitly: self.imageLable01.setPixmap(QPixmap(qImg)) and pass bytesPerLine + 1

Overdrivr Over a year ago

Any documentation that mentions numpy format is always RGB888 ?

Mark Carpenter Jr Over a year ago

Doesn't always have to be RGB888, from teh qt5 docs, doc.qt.io/qt-5/qimage.html#image-formats a list of supported formats. Of course, you'll have to make sure your numpy array has the right data.

Matthias Over a year ago

@MarkCarpenterJr Is there any way to determine which image format I need? Tried several from your link but none works.

fferri Over a year ago

With OpenCV you want to use QImage.Format_BGR888 as OpenCV uses BGR, not RGB.

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Sergio Montazzolli · Accepted Answer · 2018-06-11 15:01:17Z

23

Just complementing the answer of AdityaIntwala, if the image appears to be red or blue, it is because the format is not RGB, but BGR (the inverse). In this case, use the QImage.rgbSwapped method to correct:

height, width, channel = cvImg.shape
bytesPerLine = 3 * width
qImg = QImage(cvImg.data, width, height, bytesPerLine, QImage.Format_RGB888).rgbSwapped()

answered Jun 11, 2018 at 15:01

Sergio Montazzolli

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1 Comment

Hugs Over a year ago

If you've got channel as a variable, why hardocde 3 in there?

SkyCityRuler · Accepted Answer · 2016-03-08 00:38:09Z

8

#image is the numpy array that you got from cv2.imread(example_image.jpg)

image = QtGui.QImage(image, image.shape[1],\
                            image.shape[0], image.shape[1] * 3,QtGui.QImage.Format_RGB888)
pix = QtGui.QPixmap(image)

self.scene.addPixmap(pix)

answered Mar 8, 2016 at 0:38

SkyCityRuler

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Comments

JTIM · Accepted Answer · 2019-10-04 11:22:46Z

6

Hate to add to the large number of answers, but as this was the only thing that worked for me I will, in case others run into the same issue.

As mentioned here on GitHub

Wrap the numpy array/ndarry in a np.require(array, np.uint8, 'C') call first, such as:

arr2 = np.require(arr, np.uint8, 'C')
qImg = QtGui.QImage(arr2, width, height, QtGui.QImage.Format_RGB888)

edited Oct 4, 2019 at 11:22

JTIM

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answered May 30, 2019 at 20:51

so860

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Comments

Sajjad Aemmi · Accepted Answer · 2020-12-24 08:03:23Z

3

There is the easiest way:

from PIL.ImageQt import ImageQt 
from PIL import Image
from PySide2.QtGui import QPixmap
import cv2


# Convert an opencv image to QPixmap
def convertCvImage2QtImage(cv_img):
    rgb_image = cv2.cvtColor(cv_img, cv2.COLOR_BGR2RGB)
    PIL_image = Image.fromarray(rgb_image).convert('RGB')
    return QPixmap.fromImage(ImageQt(PIL_image))

answered Dec 24, 2020 at 8:03

Sajjad Aemmi

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Comments

Ivan · Accepted Answer · 2023-12-20 08:26:29Z

2

Here's my take on this:

def convert_nparray_to_QPixmap(self,img):
    h,w,ch = img.shape
    # Convert resulting image to pixmap
    if img.ndim == 1:
        img =  cv2.cvtColor(img,cv2.COLOR_GRAY2RGB)

    qimg = QImage(img.data, w, h, w*ch, QImage.Format_RGB888) 
    qpixmap = QPixmap(qimg)

    return qpixmap

edited Dec 20, 2023 at 8:26

answered Dec 4, 2020 at 4:00

Ivan

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1 Comment

Yost777 Over a year ago

This is incorrect. img.shape is [h, w, (channels)] and bytesPerLine = channels * width. Also note QImage(data, width, height, (bytesPerLine), QImage.Format)

smoothumut · Accepted Answer · 2022-10-04 14:05:02Z

1

AdityaIntwala's answer was close but it didnt work for me. the cvImg.data gave an error like 'argument 1 has unexpected type 'memoryview'. So I have removed the 'cvImg.data' and passed the cvImg.tobytes() as bytes, and it worked

height, width, channel = cvImg.shape
bytesPerLine = 3 * width
qImg = QImage(cvImg.tobytes(), width, height, bytesPerLine, QImage.Format_RGB888).rgbSwapped()

then I have set the pixmap as shown below

self.imageLabel.setPixmap(QPixmap(qImg))

answered Oct 4, 2022 at 14:05

smoothumut

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Comments

jack chyna · Accepted Answer · 2022-04-14 12:49:22Z

0

  image=cv2.imread("your_image.png")
  image = QtGui.QImage(image, image.shape[1],image.shape[0], image.shape[1] * 3, QtGui.QImage.Format_BGR888)
  pix = QtGui.QPixmap(image)
  self.image.setPixmap(QtGui.QPixmap(pix))

answered Apr 14, 2022 at 12:49

jack chyna

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1 Comment

Luke_ Over a year ago

Hi and welcome to stack overflow, posting an answer with only a code block is not recommended, its better to have some text around it explaining how and why this works

Andreas Violaris · Accepted Answer · 2023-03-27 11:04:57Z

0

When using OpenCV to read an image, the output is in BGR format. However, before running QImage, you need to convert BGR to RGB.

Please convert using cv2.cvtColor(img,cv2.COLOR_BGR2RGB). If you convert BGR to RGB using other solutions, such as img = img[:,:,(2,1,0)], it may not be complete.

edited Mar 27, 2023 at 11:04

Andreas Violaris

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answered Mar 22, 2023 at 10:16

Sinthawee

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