Need advice on getting HSI color from an Image

[ramstormrage]

Thank you. Ill post again when I get stuck or confused again.

[marcel]

You're welcome...
Just one thing: the signal I mentioned earlier should be emitted from the label's mousePressEvent.

[ramstormrage]

Hello again.

I subclassed QLabel and got to the point where I assign the position of the mouse event to a QPoint. Now, I understand that I need to use this QPoint to get the QRgb value of whatever is underneath. Question, how do I do this?

Here you should use the pixmap() property of QLabel to get the QRgb at the position where the mouse was clicked inside the label.

[marcel]

Oh, yes... Forgot all about that. QPixmap doesn't expose pixel data. You could convert it to a QImage, although this adds a bit of extra overhead:

QImage img = pixmap()->toImage();
 
.... later, in mousePressEvent
QRgb color = img.pixel(mouseX, mouseY);

QImage img = pixmap()->toImage();

.... later, in mousePressEvent
QRgb color = img.pixel(mouseX, mouseY);

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You could create a member QImage so you don't have to convert the pixmap at every mouse click.

See QImage::pixel
QPixmap::toImage and QLabel::pixmap()

[ramstormrage]

Ok Ill give it a go thanks.

Marcel, Id like to put in a few more questions if you dont mind. If my custom frame is on a dialog, whats the easiest way to return to Main Window to pick a color then return again to the dialog to display the color? I understand that the dialog should be modeless..

[marcel]

Yes, the dialog should be modeless, otherwise you couldn't interact with the main window. You could set the flags of the dialog to be Qt::Tool. This is usually done for palette windows, like in Photshop and Visual Studio.

Once you select a color in the main window you could transmit it to the dialog via a signal. The signal should be emitted by the main window itself or by an object the main window contains.

In order to add a custom slot to the dialog you will have to subclass it.

[ramstormrage]

Alright! Im learning new stuff..
Ok thanks again, youve been a great help.

[marcel]

no problem