[Development] About copying the image buffer with alpha blending

[Samuel Rødal]

On 08/29/2012 09:53 AM, ext song.7.liu at nokia.com wrote:
> Hi,
> 
>  
> 
> We found that QPainer::drawImage takes 30~50ms for one 150*114 image, it
> seems a little slow.
> 
>  
> 
> One quick optimization to try is: we want to do the memory copy to the
> backing store buffer directly instead of using the PaintRasterEngine.
> 
> So from Qt, is there a helper function can copy the memory of image with
> alpha blending ?

Hmm, the raster paint engine should be quite efficient at doing alpha
blending, especially if you have NEON optimizations. Qt doesn't provide
any other API to do alpha blending.

Are you also scaling or transforming the image? 30-50ms seems a bit much
for just a blend operation as you say.

--
Samuel