[FIXED] How to configure color when convert CV2 numpy array to QImage?

Issue

The program is based on pyqt and opencv. I plan to read and process image with opencv while using QT as GUI.

when I open a gray image, The result is OK. But it will change the color of image when opening a color image. I guess it's because I made mistake when I convert numpy array to OImage type, but I can't figure out how to correct it.

# -*- coding: utf-8 -*-
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys

import cv2
from cv2 import cv

QTextCodec.setCodecForTr(QTextCodec.codecForName("utf8"))

class MainWindow(QMainWindow):
    def __init__(self,parent=None):
        super(MainWindow,self).__init__(parent)
        self.setWindowTitle("Show Image with pyqt")

        self.imageLabel=QLabel()
        self.imageLabel.setSizePolicy(QSizePolicy.Ignored,QSizePolicy.Ignored)
        self.setCentralWidget(self.imageLabel)

        self.image=QImage()

        self.createActions()
        self.createMenus()

        self.cv_img = None

    def createActions(self):
        self.fileOpenAction=QAction(QIcon(":/fileopen.png"),self.tr("Open"),self)
        self.fileOpenAction.setShortcut("Ctrl+O")
        self.fileOpenAction.setStatusTip(self.tr("Open the file"))
        self.connect(self.fileOpenAction,SIGNAL("triggered()"),self.slotOpenFile)

        self.exitAction=QAction(QIcon(":/filequit.png"),self.tr("Quit"),self)
        self.exitAction.setShortcut("Ctrl+Q")
        self.setStatusTip(self.tr("Quit"))
        self.connect(self.exitAction,SIGNAL("triggered()"),self.close)

    def createMenus(self):
        fileMenu=self.menuBar().addMenu(self.tr("File"))
        fileMenu.addAction(self.fileOpenAction)
        fileMenu.addAction(self.exitAction)


    def slotOpenFile(self):
        fileName=QFileDialog.getOpenFileName(self,self.tr("Open a file"),\
            ".",self.tr("Image File(*.png *.jpg *.jpeg *.bmp)"))

        cvfilename=fileName.toLocal8Bit().data()

        if fileName.isEmpty()==False:

            cvfilename=fileName.toLocal8Bit().data() #convert Qstring to char*
            self.cv_img = cv2.imread(cvfilename) #read image with opencv
            cv2.imshow("Show Image with Opencv",self.cv_img) #show image with opencv, this is the right result

            self.image =QImage(self.cv_img.tostring(),\
                self.cv_img.shape[0],self.cv_img.shape[1],QImage.Format_RGB888) #convert numpy array to QImage
            self.imageLabel.setPixmap(QPixmap.fromImage(self.image))
            self.resize(self.image.width(),self.image.height())

app=QApplication(sys.argv)
main=MainWindow()
main.show()
app.exec_()

Solution

You need to convert the image data from BGR to RGB. You also need to swap width and height (see below) -- your code only works for images with same width and height.

self.cv_img = cv2.imread(cvfilename)

if self.cv_img != None:
    # Notice the dimensions.
    height, width, bytesPerComponent = cv_img.shape
    bytesPerLine = bytesPerComponent * width;

    cv2.imshow("Show Image with Opencv", self.cv_img)

    # Convert to RGB for QImage.
    cv2.cvtColor(self.cv_img, cv.CV_BGR2RGB, self.cv_img)

    self.image = QImage(self.cv_img.data, width, height, bytesPerLine, QImage.Format_RGB888)

Answered By - hluk