Take a screenshot and convert it to PNG but FAST !

Hi there!

My program takes screenshots using QPixmap::grabWindow(); then I convert it to PNG.

However the convertion is very slow (about 1 sec) and I need it to be much faster than that.

Any idea :confused:


In fact, I think that if I can capture the screen directly as a PNG, it would be great but I don't know how to do that.

have you checked screenshot example present in Qt Source code Qt/4.x.x/examples/desktop/screenshot

Actually I know how to take a screenshot.

I now want to convert it to PNG quickly.

Convert it from what?

from pixmap to png

QString format = "png";
Pixmap.save(fileName, format.toAscii());

Quote:

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Originally Posted by harish.surana

from pixmap to png

QString format = "png";
Pixmap.save(fileName, format.toAscii());

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Yes from Pixmap to PNG, but what I said is that this method is to slow ! (pixmap.save())

Is there any other way to take a screenshot and convert it to PNG QUICKLY ?

Quote:

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Originally Posted by fitzy

Is there any other way to take a screenshot and convert it to PNG QUICKLY ?

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Yes, switch to Windows, QPixmap::toImage() is a no-op there. BTW. You don't convert it from pixmap to png, you convert it from pixmap to image and then save it as png.

Quote:

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Originally Posted by wysota

Yes, switch to Windows, QPixmap::toImage() is a no-op there. BTW. You don't convert it from pixmap to png, you convert it from pixmap to image and then save it as png.

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You're right, but which function should I use ?

Quote:

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Originally Posted by fitzy

You're right, but which function should I use ?

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I don't understand your question. What function do you mean? Are you sure you understood my last reply?

I'm sorry, here is what I meant :

Quote:

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Originally Posted by wysota

You don't convert it from pixmap to png, you convert it from pixmap to image and then save it as png.

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my answer :

Quote:

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Originally Posted by fitzy

You're right.

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Quote:

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Originally Posted by wysota

Yes, switch to Windows, QPixmap::toImage() is a no-op there. BTW.

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You are talking about win32, right ? If you do, which specific function should I use ?

if I understood that correctly:
use QPixmap::toImage(). It just happens to be fast on windows because there is nothing (or not much) to do internally. For you as a Qt user you always do grabWindow(), then QPixmap::toImage(), then QImage::save().

(This sequence just happens to be faster on the windows platform.)

Quote:

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Originally Posted by caduel

if I understood that correctly:
use QPixmap::toImage(). It just happens to be fast on windows because there is nothing (or not much) to do internally. For you as a Qt user you always do grabWindow(), then QPixmap::toImage(), then QImage::save().

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That's exactly what I meant - QPixmap::toImage() is a no-op on Windows. It's probably a no-op if you use the raster painting engine on X11 as well but I'm not sure of that.