[haiku-3rdparty-dev] Re: BPictureButton transparency ?
- From: "Stephan Assmus" <superstippi@xxxxxx>
- To: haiku-3rdparty-dev@xxxxxxxxxxxxx
- Date: Mon, 27 Dec 2010 23:36:17 +0100
Hi,
sorry for not reading all mails in the thread before replying... a few remarks,
though:
Von: Michael Pfeiffer <michael.w.pfeiffer@xxxxxxxxx>
> Am 27.12.2010 um 21:41 schrieb Tomas Wilhelmsson:
>
> > Is it posible to make a BPictureButton Transparent somehow?
>
> If the bitmap contains transparency information (alpha values)
> setting the drawing and blending mode after BeginPicture(...)
> is required IIRC.
> view->SetDrawingMode(B_OP_ALPHA);
> view->SetBlendingMode(B_PIXEL_ALPHA, B_ALPHA_COMPOSITE);
> or
> to apply the alpha value from the high color to the bitmap
> when it is drawn:
> view->SetHighColor(0, 0, 0, alpha)
> view->SetDrawingMode(B_OP_ALPHA);
> view->SetBlendingMode(B_CONSTANT_ALPHA, B_ALPHA_COMPOSITE);
B_ALPHA_COMPOSITE is only appropriate when you have the view that is drawing
attached to a BBitmap itself. On the screen, alpha operations can always assume
a non-transparent background, against which they render, which is what
B_ALPHA_OVERLAY means.
> Not sure if a picture overwrites the drawing modes when it is draw;
> if it does you probably want to save and restore the state using
> view->PushState() after BeginPicture and
> view->PopState() before EndPicture.
Yes, good point.
Best regards,
-Stephan
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