On 27 Apr 2000 18:35:08 +0200, Thomas Willhalm <tho### [at] willhalmde>
wrote:

>Mmmh, I don't like the idea of saving a temporary file that has several
>times the size of the final image. Perhaps you should consider to apply
>the filter on the fly. I know that you need more than one pixel a time for
>several of the exististing and proposed filters. Perhaps it is possible
>to determine which one you need and forget the others.

A few thoughts come to mind: 

Not all filters can be performed "on the fly."

Photoshop, probably the most respected image processing program on the
planet, uses its own swap file to store temporary image data while
processing an image. This swap file easily grows to many times the
size of the original image. It's just the nature of image processing. 

I will admit that the POV post_processing represents an unusual
situation, in that we have so many additional attributes per pixel, in
addition to the typical R, B, and G values. If all these values are
stored in a temp file, it will indeed be many times larger than the
final output file. On the bright side, at least this file will be
deleted, and isn't permenant.   :)

Also this large array of potential attributes to work with, offers
many interesting possiblities for filters that can't be implemented
in a 2D program like Photoshop. For example, we have the potential to
create a *much better* "trace contour" filter than the one in
Photoshop. The one in Photoshop is based solely on altering the tonal
range of the image, with no knowledge of the actual geometry of the
scene. In our case we can not only take tonal information into
account, but we have access to the actual geometry of the scene. We
can find exactly where the edge of an object is, and not have to guess
based on a change in pixel brightness.

So yes, some filters would need large amounts of memory or temp/swap
files, but there is probably little we can do about it, especially for
some of the proposed filters. We could probably at least arrange to
store only the attributes that a given filter actually needs, instead
of storing everything. That way, a extremely large temp file would
only be generated if you used a filter that required one.

Later,
Glen Berry

( Remove the "7" from 7no### [at] ezwvcom to email me. )

Post a reply to this message