Just what I was looking for. I already live with using qt private stuff
:)
Many thanks.
Le 25-02-2018 20:55, Allan Sandfeld Jensen a écrit :
On Sonntag, 25. Februar 2018 20:23:32 CET maitai wrote:
Hello,
Seems quite basic, but I need a **fast** way to know if a QImage is
just
full transparent. I know the size in advance (256x256). If it were a
QPixmap I would use cacheKey() and compare with the cacheKey of a full
transparent image. For a QImage I can compare it with a preset
transparent image, or extract the alpha channel, or etc of course. But
I
need a really fast way.
Any idea?
There is a private API for that which QPixmap uses
QImageData::checkForAlphaPixels() can be accessed via QImage::d_ptr()-
checkForAlphaPixels().
Of course being private API there is not guarantee it will keep
working, and
if you use it you might not be able to link with newer Qt versions.
You can ofcourse also just look at the code in qimage.cpp and do
something
similar.
`Allan
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