strange pcomb behaviour: -x -y is different to -y -x

radiance-dev
1

Dear devs,

I've noticed a strange behaviour of Radiance's pcomb command. This is
with the latest HEAD from today. Here is how to replicate this:

Create a test HDR

$ pcomb -x 400 -y 300 -e 'lo=(x/400)' > test.hdr

now extract pixel brightness, and re-assemble into a new HDR:

pvalue -d -b -h -H test.hdr |pvalue -r -d -b -h -x 400 -y 300 > test_out_xy.hdr

This produces a 300x400 (portrait) image, not 400x300 (landscape) as I
expected. As a result, the scanlines are all wrapped:

http://www.jaloxa.eu/pickup/test_out_xy.hdr

BUT

If I reverse the -x and -y options, the result is as expected 400x300
(landscape):

pvalue -d -b -h -H test.hdr |pvalue -r -d -b -h -y 300 -x 400 > test_out_yx.hdr

http://www.jaloxa.eu/pickup/test_out_yx.hdr

is this a bug or a known quirkyness of pcomb? AFAIK, the order of
command-line options is irrelevant with most (all?) other commands.

Have a very good weekend

Kind regards

Axel

2

Hi Greg,

I did read the pcomb man page several times, but still managed to miss this bit:

"The ordering of the -y and +x options determines whether the scanlines are sorted along x or along y"

Apologies for this oversight. I guess it escaped me because I have never come across an 'x y' ordered image. Didn't even know this was possible, to be honest.

Many thanks for clarifying. No bug, then, just me learning new things.

Have a good weekend.

Axel

ยทยทยท

On 19/02/16 19:25, Gregory J. Ward wrote:

Hi Axel,

If you read the pvalue man page very carefully, you'll note that the resolution option order matters for this command. However, it doesn't matter for pcomb, which always produces "-y +x" ordering. So, to reconstruct the image without the header information, you need to adhere to this ordering in pvalue.

Does this make sense?

_Greg

From: Axel Jacobs <[email protected]>
Subject: [Radiance-dev] strange pcomb behaviour: -x -y is different to -y -x
Date: February 19, 2016 9:49:24 AM PST

Dear devs,

I've noticed a strange behaviour of Radiance's pcomb command. This is
with the latest HEAD from today. Here is how to replicate this:

Create a test HDR

$ pcomb -x 400 -y 300 -e 'lo=(x/400)' > test.hdr

now extract pixel brightness, and re-assemble into a new HDR:

pvalue -d -b -h -H test.hdr |pvalue -r -d -b -h -x 400 -y 300 > test_out_xy.hdr

This produces a 300x400 (portrait) image, not 400x300 (landscape) as I
expected. As a result, the scanlines are all wrapped:

http://www.jaloxa.eu/pickup/test_out_xy.hdr

BUT

If I reverse the -x and -y options, the result is as expected 400x300
(landscape):

pvalue -d -b -h -H test.hdr |pvalue -r -d -b -h -y 300 -x 400 > test_out_yx.hdr

http://www.jaloxa.eu/pickup/test_out_yx.hdr

is this a bug or a known quirkyness of pcomb? AFAIK, the order of
command-line options is irrelevant with most (all?) other commands.

Have a very good weekend

Kind regards

Axel

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http://www.radiance-online.org/mailman/listinfo/radiance-dev