Polar Coordinates filter bug(?)

LB
Posted By
leo_bleicher
Apr 29, 2004
Views
419
Replies
5
Status
Closed
I’m having a problem when trying to apply the Rectangular to Polar version of this filter to a moderate sized image. Using a file 5000×2500 pixels with a black square of 2490×2490 pixels placed 5 pixels in from the top right corner, and applying the polar filter generates the expected black half oval, but also two triangular artifacts in the top and bottom right corners.

This does not happen when the canvass size is less than 4000×2000, and gets worse the larger the canvass size. The problem exists in CS and 7.0, but is even worse in 7.0.

Has anyone else seen this behavior or know of a way around it?

I have tried working on one channel at a time and this does not help, also conversion to greyscale does not help. My system is operating with ~500MB RAM dedicated to PShop.

Thanks,
Leo
Related Tags
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P
Phosphor
Apr 29, 2004
Hmm…

I just did the exact thing you’ve described, and Polar Coordinates works just fine. It provided pretty much exactly what I expected. No glitches, no unexpected image anomalies.

I’m working with Photoshop 7.0.1 under OS X 10.3.3 with 640 MB of RAM, and it took only 6 seconds to render the filter’s change.

Soooo, what this means is that it’s not a bug in Photoshop, but a problem with your system. What that problem is, I have no idea.

If I could help, I would.
LB
leo_bleicher
Apr 29, 2004
Thanks for checking on that…I am running on Win XP, various pIII and pIV systems all show the same error. Perhaps I should try harder to get a Mac!

Thanks again,
Leo
JB
Jonathan_Balza
Apr 29, 2004
Well, I’m getting the error as well. Same exact circumstances as Leo describes. Anything below ~4000px gets me no artifacts, but above, I get the craziness shown here <http://www.balzasteel.com/temp/errors.gif>. (Red added after, of course.)

At first I thought it had something to do with the interpolation method, but that doesn’t do anything. Same results with all methods. Could it be some kind of averaging going on?

Here is something interesting, though: at 4000px wide, it performs correctly, but the artifacts begin to appear at around 4300px, and move up from there, getting larger and larger until at around 8000px, they actually intrude into the half oval that appears… The effect gets worse and worse.

My machine is Photoshop CS running on Windows XP, so I wonder if this is specific to Windows.
JR
John_R_Nielsen
Apr 30, 2004
I noticed something like this about a year ago with v7, Win98SE. Above a certain size image, Polar Coordinates produced a "reflection" of the polar image, spreading outwards. . .sort of as if it were being viewed though a shiny tube. I hope that makes sense; I guess you could say that the conversion turned inside out.

Chris responded that he could not find anything in the code to account for this.
CC
Chris_Cox
Apr 30, 2004
4000 sounds suspicious – that is close to an old limit in the math (that I thought I had fixed, darn it!). We’ll take another look.

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