Processing and Displaying Image on Widget

[mhb88]

My guess is that you are accessing memory areas that are not valid while looping over the image.
Your inner loop's step size is 1 uint per loop, an uint is usually 4 bytes.
But your image format is one byte per pixel.

oh, Wow!! I can't believe that I let this warning confuse me!!

uchar *QImage::scanLine(int i)
Returns a pointer to the pixel data at the scanline with index i. The first scanline is at index 0.
The scanline data is aligned on a 32-bit boundary.
Warning: If you are accessing 32-bpp image data, cast the returned pointer to QRgb* (QRgb has a 32-bit size) and use it to read/write the pixel value. You cannot use the uchar* pointer directly, because the pixel format depends on the byte order on the underlying platform. Use qRed(), qGreen(), qBlue(), and qAlpha() to access the pixels.

thank you very much anda_skoa

cheers

[mhb88]

as you see in my code I posted at the beginning of this thread, I have bunch of classes already in my project and I am going to add a few more as I progress in my project. I came up with the idea to add a TextEdit to my mainwindow.ui and called it Console to display some text there through out my code.
I want to be able to do this from all my classes.
At first I thought there is no easier task than this, but apparently I can't find a solution.
would you guys help me on this?

cheers

[anda_skoa]

You have different options:

- add signals that emit new "console" text to classes that need it and connect to the text edit or a slot in main window
- pass the pointer to the text edit or main window to wherever this is needed
- make the pointer to the text edit or the main window globally accessible

Cheers,
_

[mhb88]

OK, I got everything working as the base of my project. At this point I can communicate with camera, and receive its frames, and just display them in my widget.
But I have an issue.
My camera supports up to 100 frames/sec, but I am barely displaying 15 frames/sec.
My camera resolution is 480x640 and I am just receiving 8bits grayscale frames. So each frame has 480 x 640 x 8 = 300KBytes of data and if I want to receive them at rate of 100 fps, I have to receive them 300KBytes/frame x 100 frames/sec = 30000 KBytes/sec, about 30MBytes/sec, which is half of the speed of the USB2.0. So I think my USB2.0 should be able to do handle that amount of data transfer.

So I think the issue is in my software, but I am not doing any processing in my code, I am just displaying frames. I have created a class with a paint event, and I have promoted a Qwidget to this class to display on it.

I don't know if Qwidget can handle transferring this amount of data?
Does any one has any suggestion or solution?

cheers

[anda_skoa]

For such high througput rendering you probably have to use a more direct rendering approach, e.g. OpenGL.

It might be worthwhile to look into creating a QCamera backend and then use the existing video widget infrastructure.

Cheers,
_

[mhb88]

Do you know any tutorials that start from foundation and builds up to it?
I don't have any experience with OpenGL.
I found most tutorials to be about QGLWidget.
But in the new versions of Qt 5, QOpenGLWidget is intended to be a modern replacement for QGLWidget.
I haven't been able find a good tutorial for QOpenGLWidget.

cheers

[anda_skoa]

No, sorry, I haven't had anything to do with that yet myself either.

Cheers,
_

[mhb88]

I was wondering if this would work?
a function is getting a pointer to a QImage as a parameter.
I want to copy the entire QImage to a buffer of that is going to hold 100 QImages.

public:
    void function(QImage *frame);
 
protected:
    enum{size = 100};
    QImage *data[size];
    int front; // points to the front of the buffer

public:
    void function(QImage *frame);
    
protected:
    enum{size = 100};
    QImage *data[size];
    int front; // points to the front of the buffer

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void Buffer::function(QImage *frame)
{
     ++front; // Increment front.
     if (front == size)
         front = 0; // Wrap around.    
 
     data[front] = frame;
}

void Buffer::function(QImage *frame)
{
     ++front; // Increment front.
     if (front == size)
         front = 0; // Wrap around.    

     data[front] = frame;
}

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cheers

[anda_skoa]

Sure, why not.
I assume you handle deletion of the QImage pointers somewhere else?

Cheers,
_