[Qt-interest] QImage and ARGB32_Premultiplied

[Mihail Naydenov]

I didn't knew setAlphaChannel is deprecated.  This is unfortunate.

Do you know way it is deprecated? Because I dont see a way to mimic its effect 
without iterating the pixels manually.

I other words - what composition mode will apply a grayscale (Indexed8) src 
image to the alpha of a ARGB32(_Premultiplied) dest image?

Thanks
MihailNaydenov



----- Original Message ----
> From: Thiago Macieira <thiago at kde.org>
> To: qt-interest at qt.nokia.com
> Sent: Sun, January 30, 2011 1:12:26 AM
> Subject: Re: [Qt-interest] QImage and ARGB32_Premultiplied
> 
> On Saturday, 29 de January de 2011 14:41:14 Joshua Grauman wrote:
> > 1) If  I have one QImage that is ARGB32_Premultiplied and one that is
> > ARGB32,  if I assign one into the other (ie. image1=image2), will QImage do
> > the  conversion for me?
> 
> No. The two images will be equal (QImage is implicitly  shared). They will be 
> both of the same format, with the exact same pixel  content.
> 
> > 3) Seeing that setAlphaChannel() is deprecated, what is the  fastest way to
> > set the alpha channel to a single value for an entire  image (for an
> > ARGB32_Premultiplied QImage). Do I have to iterate over  each pixel and
> > calculate/set the premultiplied values?
> 
> Probably  by blending with another image that has an alpha channel. Iterating 
> would be  slower than doing the blend.
> 
> -- 
> Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
>   Senior Product  Manager - Nokia, Qt Development Frameworks
>       PGP/GPG:  0x6EF45358; fingerprint:
>       E067 918B B660 DBD1 105C   966C 33F5 F005 6EF4 5358
>