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Date Posted: 18:28:52 05/12/00 Fri
Author: Michel
Subject: Re: Envision is really cool! -- Yes, but...
In reply to: Ted Slusser 's message, "Re: Envision is really cool! -- Yes, but..." on 11:52:34 05/12/00 Fri

Hi Ted,

I think it is actually the VCL base class TScrollingWinControl that is not very fast. StretchDiBits is usually quite fast. I decided to derive from TScrollingWinControl for code reuse, and to stay close to the VCL, which is the same idea why all graphic classes in Envision derive from TGraphic.

I have done some testing and the scrolling in the VCL scroll box is quite slow especially on NT. If you look at the post, Flickering on NT 09:29:47 03/18/00 Sat, there is an improvement there to be made.

Envision is not as full featured and some parts are not as optimized as some commercial libraries, but I will continue to improve it.

Best regards,

> I like Envision too but I have noticed that resizing
> the TScrollBoxImage is really slow. The image I am
> viewing is a TTiffGraphic created at run-time and
> assigned to the TScrollBoxImage.Graphic property. It
> is 200dpi and 1700 x 2200, monochrome with
> Anti-aliasing turned on and ZoomMode set to
> zmFullPage. When I resize the form it is really slow
> recalculating the image. With Anti-aliasing turned
> off it is a little faster but not much. When the
> ZoomMode is zmOriginalSize it is much faster. I have
> traced the slowdown to a single Win32 API function,
> StretchDiBits().
> Does you have any ideas why this function would take
> so long? I assume that since the image is being
> resized in memory the translation is causing the
> slowdown, but should this be the case?
> Believe me, I prefer Envision to ImageLib for a wide
> variety of reasons but ImageLib does not suffer from
> this particular slowdown.
> > I must say that overall that Envision graphics
> > graphics is really cool! We have replaced our
> > Imagelib code with Envision graphics code and it is
> > working great!

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