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Re: Slow image drawing on big images [message #13855 is a reply to message #13852]

Wed, 30 January 2008 09:01

mirek
Messages: 13984
Registered: November 2005

Ultimate Member

mdelfede wrote on Tue, 29 January 2008 17:56

WOW, that was a great speed improvement !
Thanx ! Smile

Max

EDIT : I need also to implement ZOOM, PAN and a multipage interface. For PAN, no problem, I can derive from ImageCtrl.
Regarding ZOOM I wonder if there's not a fastest way than rescaling the image on the fly.... Does the main image paint code provide some stuff for resizing image on the fly, maybe with help of native code ?
For the multipage stuff I'll look tomorrow on Raster code.

Ciao

Max

IMO, forget about ImageCtrl. It was not designed for this purpose and it is about 20 lines anyway. Roll your own widget.

For zooming, just use Rescale, it is close to perfect. Also, you might prefer cached variant, use

Image CachedRescale(const Image& m, Size sz, const Rect& src);

or

Image CachedRescalePaintOnly(const Image& m, Size sz, const Rect& src);

PaintOnly means that you do not intent to access the pixel matrix anymore; Draw is then allowed to free the memory. "Cached" means you can call this function in Paint routine; if source parameters do not change, Image is restored from the cache.

Mirek

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