QImage(img.data,...) out of scope - img.data gets deleted when QImage is destroyed

gerrard87

Hi, im a newbie,
i have a livestream with overlays which are changing when hitting a keybutton. After some minutes the livestream is freezing and then second later crashing without any action or error. ive read some where that the QImage(img.data...) is going out of scope and i must delete when QImage gets destroyed or explicite copy the data. Here is my snapshot of my code.

# Display Geometrie
MyApp = QtWidgets.QApplication(sys.argv)
V = MyApp.desktop().screenGeometry()
h = V.height()
w = V.width()
HEIGHT= 1080
WIDTH = 1920

class MainWindow(QWidget):
    
        # Start Button Action    
    def pushbutton_left_Callback(self):  
        if not self.timer.isActive():
            self.loading_screen = LoadingScreen()
            self.cap = cv2.VideoCapture(1)     
                   
            if not (self.cap.isOpened()):                   
                self.noWebCam() 
                
            # for using two external webcam
            if self.spsn == True:                
                self.timer.start(5)
            else:
                self.timer.start(35)  

# +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++#
# ----------------------- Live Stream functions --------------------------#  

    def cap_img(self, cap):
        ret, img = cap.read()
        img = cv2.flip(img,1)#flip cam
        img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
        height, width, channel = img.shape
        step = channel * width        
        
        img = QImage(img.data, width, height, step, QImage.Format_RGB888)  

        if height != HEIGHT and width != WIDTH:
            img = img.scaled(WIDTH, HEIGHT)
        
        return img

    def snap_img(self, cap):
        ret, img = cap.read()
        img = cv2.flip(img,1)#flip cam
        self.snap_cv = img.copy()        

        img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
        height, width, channel = img.shape
        step = channel * width        
            
        self.snap = QImage(img.data, width, height, step, QImage.Format_RGB888)
        if height != HEIGHT and width != WIDTH:
            self.snap = self.snap.scaled(WIDTH, HEIGHT)  
           
    # Show Livestream
    def livestream_overlays(self):
        super().__init__()
        
        self.overlay_base()  
        
        # red lines as overlays
        if self.state == 1 or self.state == 2:           
            self.overlay_red()       


        elif self.state == 3:
            self.overlay_blue()
            

        # green lines as overlays (L-Button)
        if self.lvalue:
            self.overlay_green()
  
        # Show Livestream with overlays
        if self.spsn == True:                        
            img = self.img.scaled(int(w/2), int(h)) 
            self.img2 = self.img2.scaled(int(w/2), int(h))
            
            if self.state_cams == True:                  
                self.show_cam(self.img2,2) 
                self.show_cam(img,3) 
            else:                              
                self.show_cam(self.img2,3) 
                self.show_cam(img,2) 
                  
        else:
            img = self.img.scaled(w, h) 
            self.show_cam(img,1)    
            
 
    def insertShape(self, img1, lines, linewidth, color):        
        img = img1.copy()
        
        painter = QPainter()
        pixmap = QPixmap(img)
       
        painter.begin(img)
        painter.setRenderHint(QPainter.Antialiasing)
        painter.drawPixmap(img.rect(), pixmap)
        painter.setPen(QPen(colors[color], linewidth))

        for line in lines:
            painter.drawLine(line[0],line[1],line[2],line[3])
        
        return img  
           

    def overlay_base(self):

        if self.pop != None:
            if self.pop.chns != None: 
                self.ns = self.pop.chns
                self.pop = None
        

        img = self.cap_img(self.cap)             
        
        img = self.insertShape(img, self.yellowline, 2, 'yellow') 
               
        if self.spsn == True:
            img2 = self.cap_img(self.cap2) 
            self.img2 = self.insertShape(img2, self.yellowline, 2, 'yellow')
                
                
        if self.spsn == True:
            if self.state_cams == True:
                self.set_nsheet(img,self.ns)  
            else:
                self.set_nsheet(self.img2,self.ns)  
        else:
            self.set_nsheet(img,self.ns)  

        # set paramenter overlays
        if visible_parameter_overlays ==1:
            if self.spsn == True:
                if self.state_cams == True:
                    img = self.set_parameter_overlays(img)                                      
                else:
                    self.img2 = self.set_parameter_overlays(self.img2) 
            else:
                img = self.set_parameter_overlays(img)          
            
                
        self.img = img 

    def overlay_red(self):
        redlines = self.outputs['redlines']        
        self.img = self.insertShape(self.img, redlines, 2, 'red') 

        if self.spsn == True:
            self.img2 = self.insertShape(self.img2, redlines, 2, 'red')     

    def overlay_blue(self):
        bluelines = self.outputs['bluelines']
        self.img = self.insertShape(self.img, bluelines, 2, 'blue') 

        if self.spsn == True:
            self.img2 = self.insertShape(self.img2, bluelines ,2, 'blue')    


    def overlay_green(self):
        greenlines = self.outputs['lines']
        self.img = self.insertShape(self.img, greenlines, 2, 'green')  
        if self.spsn == True:
            self.img2 = self.insertShape(self.img2, greenlines ,2, 'green')    

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)    
    mainWindow = MainWindow()    
    mainWindow.showFullScreen()

    sys.exit(app.exec_())

I dont know how i must do it. Does somebody has a idea or a example what i need to do?
Thank You all

JonB

@gerrard87
I'm just not sure with Python's reference counting and garbage collection whether your img.data stays in existence, as required by that QImage constructor. Why don't you try something like:

img = QImage(width, height, QImage.Format_RGB888)  
img.loadFromData(img.data, len(img.data))

which I believe manages the data for you to see whether it makes any differenece?

If your app crashes after a while check computer's free memory available to see if it's endlessly allocating.

Christian Ehrlicher

I already told them on so that he simply should use QImage::copy() to make sure the image data is copied. But ...

gerrard87

@JonB said in QImage(img.data,...) out of scope - img.data gets deleted when QImage is destroyed:

img.loadFromData(img.data, len(img.data))

i get a Error when i using:

        img = QImage(img.data, width, height, step, QImage.Format_RGB888) 
        img.loadFromData(img.data, len(img.data))

AttributeError: 'QImage' object has no attribute 'data' ? Whats wrong?

jsulm

@gerrard87 said in QImage(img.data,...) out of scope - img.data gets deleted when QImage is destroyed:

Whats wrong?

The error message already told you what is wrong.
Also easy to find out that there is no data property in QImage (read its docu).
What you need is rather https://doc.qt.io/qt-5/qimage.html#bits-1

But i don't understand what you are doing.
You create a QImage from another one (first line), then you call loadFromData from exact same image (second line) - what is the point?

JonB

@gerrard87 said in QImage(img.data,...) out of scope - img.data gets deleted when QImage is destroyed:

AttributeError: 'QImage' object has no attribute 'data' ? Whats wrong?

But I copied my img.data from your img = QImage(img.data, width, height, step, QImage.Format_RGB888) . I did say "something like", you are supposed to figure it yourself....

Oh, I see, you are using the same-named local img variable for two different types of image object! Just why Python is so meh....

You are using img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB). So use a different variable name for the QImage now.

gerrard87

@JonB said in QImage(img.data,...) out of scope - img.data gets deleted when QImage is destroyed:

@gerrard87 said in QImage(img.data,...) out of scope - img.data gets deleted when QImage is destroyed:

AttributeError: 'QImage' object has no attribute 'data' ? Whats wrong?

But I copied my img.data from your img = QImage(img.data, width, height, step, QImage.Format_RGB888) . I did say "something like", you are supposed to figure it yourself....

Oh, I see, you are using the same-named local img variable for two different types of image object! Just why Python is so meh....

You are using img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB). So use a different variable name for the QImage now.

mmh so just change this?

    def cap_img(self, cap):
        ret, img = cap.read()
        img = cv2.flip(img,1)#flip cam
        img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
        height, width, channel = img.shape
        step = channel * width        
        
        img_new= QImage(img.data, width, height, step, QImage.Format_RGB888)  

        if height != HEIGHT and width != WIDTH:
            img = img.scaled(WIDTH, HEIGHT)
        
        return img

would that be enough? its not working because scaled is not found (object has no attribute 'scaled')

Christian Ehrlicher

@gerrard87 said in QImage(img.data,...) out of scope - img.data gets deleted when QImage is destroyed:

    img_new= QImage(img.data, width, height, step, QImage.Format_RGB888)  

    if height != HEIGHT and width != WIDTH:
        img = img.scaled(WIDTH, HEIGHT)

Don't you think there's something wrong here?

And you forgot the copy - just saying it for the third time...

JonB

@gerrard87 said in QImage(img.data,...) out of scope - img.data gets deleted when QImage is destroyed:

its not working because scaled is not found (object has no attribute 'scaled')

Why do you think that is? You should understand what you are doing/changing, not just copy & paste.

gerrard87

@Christian-Ehrlicher said in QImage(img.data,...) out of scope - img.data gets deleted when QImage is destroyed:

I already told them on so that he simply should use QImage::copy() to make sure the image data is copied. But ...

sorry i just started with python and im still learning. I got this code from a friend and now i must work with it.
Can you help me how the line with Qimage::copy() must look like? Still dont know how to make it work.

SGaist

Hi,

I would recommend that you do all image manipulation with OpenCV since you have the original data in it.

Then

return QImage(img.data, width, height, step, QImage.Format_RGB888).copy()

gerrard87

@SGaist said in QImage(img.data,...) out of scope - img.data gets deleted when QImage is destroyed:

return QImage(img.data, width, height, step, QImage.Format_RGB888).copy()

ok thank you, but what you mean with doing all the stuff with OpenCV? What kind of function in particular? I thought i was already doing everything with OpenCV?!
THank You all.

SGaist

You are not doing the resizing with OpenCV.