setPixmap and Paint Event

Hi all,

I´m trying to do some simple Qt experiments... like load and manipulate pixmaps.

Why this piece of code does not work?

Code:

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image = QImage(256, 256, QImage::Format_RGB32);
   QRgb value;
   value = qRgb(189, 149, 39); // 0xffbd9527
   image.setPixel(1, 1, value);
   value = qRgb(122, 163, 39); // 0xff7aa327
   image.setPixel(0, 1, value);
   image.setPixel(1, 0, value);
   value = qRgb(237, 187, 51); // 0xffedba31
   image.setPixel(2, 1, value);
   pixmap.fromImage(image,Qt::ColorOnly);
   ui.label->setPixmap(pixmap);

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As you can see, is a part of one example from Qt Image documentation. This code is placed in a slot, and it is connected to a button (or not, it is not important).
I only want to load and show a pixmap when the button has been pressed, at least as a first approx.
Now i´m reading something related to paint Events, and maybe this is the way to manipulate pixmap, but i have no much time.

Thanks

Quote:

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Why this piece of code does not work?

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What do you mean by "not work"?
What do you see?

Thanks for your answer,

When the button is pressed, it seems that nothings occurs. However, if i load a bmp file, or jpg.. the file is loaded and shown when i signal the slot.

I think that i didn´t understand anything about Qimage, and maybe i need to read more about Qpainter?

Sorry about my english, but I ´ll try to explain what is supposed I want to do:

I need to show in a user interface several data patterns. These patterns are 2-Dim arrays of 2 bytes words. Like a PAL video frame, more or less. First of all, i want to show these patterns and make some changes in them, pixel by pixel. (like a inversion operation).
Also, these 16bits words need to be converted to an apropiate color, something like first possible value (0x0000) will be a dark blue color, and the last (0xFFFF) will be dark red.

What is the best way to do this?

Thanks again

Quote:

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When the button is pressed, it seems that nothings occurs.

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can you show the connect() line you are using to connect the button to the slot?
Also, when you start the program from a console or a debugger, look at the output, see if any signal/slot connection warnings come up.
Once we solved the signal/slot connection we can look in to the rest.

Its a simple (i thing) connect:

Code:

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connect (ui.paintButton, SIGNAL (clicked()), this, SLOT (initPixmap()));

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.

Interface has been created with Qt Designer, so "ui" represents that object.
initPixmap() function contains the code I posted before.

Same line works if i load a bmp file:

Code:

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pixmap.load("xxxx.bmp",const char *,Qt::Flags);
ui.label->setPixmap (pixmap);

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, and there aren´t console message indicating some like "No such slot/signal...."

I think i´m missing some important concept about Qt graphics framework.

thanks again

Quote:

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Same line works if i load a bmp file:

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So if you put these two lines in the slot instead of the QImage conversion code, you get an image when the button is clicked?

I see no problems in the code you posted so far.

Quote:

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I think i´m missing some important concept about Qt graphics framework.

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You are not doing any painting your self, so it plays no role, at least for the code you posted.

The problem is the following line:

Code:

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pixmap.fromImage(image,Qt::ColorOnly);

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It should be:

Code:

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pixmap = QPixmap::fromImage(image,Qt::ColorOnly);

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I fall in that pit every time! :-)
Well spotted!