🚀 go-pugleaf

Hi Kap, actually after a night's thought about it i figured it is
impossible to do a rotation without creating holes unless the image is
infintely large - of course you can kinda fix them by duplicating the
closest pixels to the pixels that fall out of the source image. 

another option which seems to be the way you did it (at least the way i 
interprete your response) is to ignore the pixels that need to be 
reconstructed using non-existent pixels, and end up with a "rotated" 
image that has blank strips in it.

for me, both would work 'cuz the object in my images are in the center so 
i can afford to ignore the edges. but for other applications i guess i 
still need to be educated.

the reverse rotation is just replacing your theta with -theta :) then 
when you do the interpolation you will be working with pixel values you know.

thanks. 

Xiaoyi

On Tue, 16 Jan 1996, Kap Shiwram wrote:
> 
> Hmm, to keep it in the range of the source image, couldn't you use AND 
> with your index?  Um, this is how I use to do it - the rotation failed 
> but it was never out of the range of the source file. :)  Um, this is 
> assuming you're using powers of 2 for the dimensions of your image of 
> course; if you're not then you might have to suffer a divide (eeek) i.e. 
> use the MOD of your index into the image and the dimensions multiplied.
> 
> Um, assuming your image dimensions are 32x32, 
> 
>    ; calculate the index [si] first
>    and si, (32*32)-1
>    lea si, [image+si]
>    movsb
> 
> I'm curious though.. could you explain how you did the reverse rotation? 
> I was thinking about this and doing landscapes or flags.  It always had 
> holes in it since I was calculating the X and Y values to plot on screen 
> but if I had just done a loop over the X and Y values then this would not 
> have happened - instead, I would have just calculated the index into the 
> image array and covered the entire area.  The problem is, I don't know 
> how to get the reverse function.  Is it just the inverse?
> 
> 
> 

Xiaoyi

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