Help with image effect

[Alex Tweedly]

I want a nice, simple (?) visual effect:

 I have two images (which may be different sizes), and I want to swap 
them over (such that each one stretches or shrinks to occupy the space 
previously taken up by the other one).

I thought this would be simple ... loop some number of times, adjusting 
the "rect" of each image - then find a suitable "wait" value to slow it 
down.

In fact, it is unbearably slow - even for medium sized images (320*240 
swapping with a 320*480) each step is clearly visible.
For 2 images of 160*120 it's almost a smooth animation - I'm not sure if 
it's just that they are smaller sizes, or if it's the fact that the 
sizes remain the same.  (all on medium laptop - Pentium P4 2.8G with 
low-end ATI graphics)

It does look OK on a top of the range Pentium laptop with ATI92xx 
graphics (my wife needs high-end hardware to play Sims :-), but that's 
not exactly typical hardware yet.

Is there some other way I should be approaching this ?

> on imageSwap pImg1, pImg2, pNumber
>   local r1, r2
>   local dtlx, dtly, dbrx, dbry
>  
>   if paramCount() < 3 then
>     put 20 into pNumber
>   end if
>  
>   put the rect of img pImg1 into r1
>   put the rect of img pImg2 into r2
>    
>   put (item 1 of r2 - item 1 of r1)/20 into dtlx
>   put (item 2 of r2 - item 2 of r1)/20 into dtly
>   put (item 3 of r2 - item 3 of r1)/20 into dbrx
>   put (item 4 of r2 - item 4 of r1)/20 into dbry
>    
>   repeat with i = 1 to pNumber
>     set the rect of img pImg1 to trunc(item 1 of r1 + i*dtlx), 
> trunc(item 2 of r1 + i*dtly), trunc(item 3 of r1 + i*dbrx), trunc(item 
> 4 of r1 + i*dbry)
>     set the rect of img pImg2 to trunc(item 1 of r2 - i*dtlx), 
> trunc(item 2 of r2 - i*dtly), trunc(item 3 of r2 - i*dbrx), trunc(item 
> 4 of r2 - i*dbry)
>   end repeat
> end imageSwap

Thanks,

-- 
Alex Tweedly       http://www.tweedly.net



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