Re: Large image re-scaling

From: Michael Cooper (crwper_at_telus.net.invalid)
Date: 06/07/04 

Date: Mon, 07 Jun 2004 03:53:22 GMT

In article <1cj2c0l673uj1d7fc21sdmrmh2fi5l5bnl@4ax.com>,
 Severian <severian@chlamydia-is-not-a-flower.com> wrote:

> On 4 Jun 2004 15:44:17 -0700, crwper@mustagh.com (Michael Cooper)
> wrote:
>
> >I have a fairly large image (21600x21600x3) which I would like to
> >enlarge to 32768x32768. I've tried several packages (GIMP,
> >ImageMagick, Paint Shop Pro, Image Genius, PhotoZoom Pro, etc.), but
> >they all seem to be trying to load the entire file into memory first.
> >I'm not terribly fussy about the interpolation technique, although I'd
> >like something better than the nearest-neighbour code I've just
> >written. Bicubic would be fine. The image is currently in TIFF format.
> >
> >I am using Windows XP, but if it helps I can always move the images
> >over to my Mac, which is running OS X.
>
> Hopefully Helpful Notes:
>
> 1. Your original image is 1.3 Gb.
> 2. The target image is 3.2 Gb.
> 3. The extra 2Gb is all interpolated and adds no real information; why
> is this excercise necessary?
> 4. Systems with 4Gb address spaces are quite unlikely to have 3.2 Gb
> of contiguous free space.
> 5. Many TIFF libraries are limited to 2Gb output.
> 6. There probably exists some program which can do what you want, but
> I don't know what it is, and it's likely to be expensive.
>
> Have you tried Photoshop?

I haven't tried Photoshop, because I don't have it. Your image sizes are
correct. I don't need the whole thing to be loaded into memory at once,
and that's sort of the point. What I need is to make the image
power-of-two in each dimension, and then I'll be using my own routines
to break it into tiles in a particular way, which are stored on disk but
only a 4 meg buffer will be kept in memory.

I've already written a "nearest-neighbour" program which uses a minimum
amount of memory to do the operation. I could, of course, write a
bicubic interpolation without too much trouble, but I thought I'd save
myself the hassle and maybe get a more general piece of software which
may be useful in the future, to boot. You know?

Sounds like Photoshop might do what I'm looking for, and certainly would
constitute a generally-useful piece of software. :) Thanks!

Michael

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