Hallo.
wxfalsecolor does not calculate values for luminance or illuminance.
Instead it uses the Radiance tool pvalue to extract this information
from the image. I am surprised that pvalue and Photosphere come up
with different values, though. Greg is probably the best to comment
on this. I myself have never used Photosphere.
The size related popup is just gives you the option to skip the pvalue
step when the image is loaded. It can take a while (especially for large
image) and for most of the features it is not necessary.
Regards,
Thomas
···
On Sun, Dec 12, 2010 at 11:36 PM, Mehmedalp Tural <[email protected]> wrote:
Hello Mr. Bleicher,
I am a PhD student at Arizona State University. I learned about the
wxfalsecolor and falsecolor2 from Radiance mailing list.
I have a question regarding the computed luminance values. I created my hdrs
using Photosphere and run pfilt to reduce their resolution (to run evalglare
faster).
I checked the average luminance of a selected region before and after
running pfilt and the results were identical under Photosphere.
However, wxfalsecolor computed the average luminance of the same region two
times more than Photosphere.
(I did not process the hdr file using any other software like Photoshop,
knowing that even cropping would change pixel values).
What could be the reason for this difference? Wxfalsecolor pops-up an
attention window for large file sizes. Is there a file size limit?
I'd appreciate your comments.
Sincerely,
Mehmedalp Tural
PhD Candidate
Herberger Institute
Arizona State U
I am not familiar with wxfalsecolor. Is it possible that it is not taking into account the EXPOSURE setting in the header? What happens when you use the -1 option to pfilt?
-Greg
···
From: Thomas Bleicher <[email protected]>
Date: December 12, 2010 9:15:05 PM PST
Hallo.
wxfalsecolor does not calculate values for luminance or illuminance.
Instead it uses the Radiance tool pvalue to extract this information
from the image. I am surprised that pvalue and Photosphere come up
with different values, though. Greg is probably the best to comment
on this. I myself have never used Photosphere.
The size related popup is just gives you the option to skip the pvalue
step when the image is loaded. It can take a while (especially for large
image) and for most of the features it is not necessary.
Regards,
Thomas
On Sun, Dec 12, 2010 at 11:36 PM, Mehmedalp Tural <[email protected]> wrote:
Hello Mr. Bleicher,
I am a PhD student at Arizona State University. I learned about the
wxfalsecolor and falsecolor2 from Radiance mailing list.
I have a question regarding the computed luminance values. I created my hdrs
using Photosphere and run pfilt to reduce their resolution (to run evalglare
faster).
I checked the average luminance of a selected region before and after
running pfilt and the results were identical under Photosphere.
However, wxfalsecolor computed the average luminance of the same region two
times more than Photosphere.
(I did not process the hdr file using any other software like Photoshop,
knowing that even cropping would change pixel values).
What could be the reason for this difference? Wxfalsecolor pops-up an
attention window for large file sizes. Is there a file size limit?
I'd appreciate your comments.
Sincerely,
Mehmedalp Tural
PhD Candidate
Herberger Institute
Arizona State U
Hi Greg.
I am not familiar with wxfalsecolor. Is it possible that it is not taking
into account the EXPOSURE setting in the header?
As I wrote, I just use "pvalue -o ..." to get the values from the image.
It works fine with rendered images and test images I have created
with pcomb. I have never used it on HDR images, though.
I wanted to include a feature that checks the header information
and warns if the images does not contain useable luminance values
(after pcond has been used for example). I'm not sure if I understand
these limitations myself correctly so I rely on the user to provide
appropriate images.
Regards,
Thomas
···
On Mon, Dec 13, 2010 at 12:19 PM, Greg Ward <[email protected]> wrote:
Hi Thomas,
The -o option should give you original values, provided as you say something hasn't happened in between to lose the calibration. I'm just throwing out guesses. I have no idea why the results would disagree, otherwise.
Cheers,
-Greg
···
From: Thomas Bleicher <[email protected]>
Date: December 13, 2010 11:14:16 AM PST
Hi Greg.
On Mon, Dec 13, 2010 at 12:19 PM, Greg Ward <[email protected]> wrote:
I am not familiar with wxfalsecolor. Is it possible that it is not taking into account the EXPOSURE setting in the header?
As I wrote, I just use "pvalue -o ..." to get the values from the image.
It works fine with rendered images and test images I have created
with pcomb. I have never used it on HDR images, though.
I wanted to include a feature that checks the header information
and warns if the images does not contain useable luminance values
(after pcond has been used for example). I'm not sure if I understand
these limitations myself correctly so I rely on the user to provide
appropriate images.
Regards,
Thomas
Mehmedalp
Since we're a bit out of ideas here could you post the output of the getinfo
command for both pictures. That might help us understand what happened to
the images.
After reading your initial email again I found one other possible reason:
wxfalsecolor ignores pixels with red value of 0. Due to the limitations of
the RGBE image format a value of 0 in one channel means a black pixel. In
real live black pixels do not exist and are therefore ignored when an
average is calculated. This was done to allow a rectangular selection over a
masked image area without the mask contributing to the average.
You can see if a pixel contributes by moving the mouse over the image after
you have loaded the data (happens automatically for small images). If you
see an r,g,b value next to pixel position in the status bar the pixel does
count. If it's a black pixel it will show only the position.
So if your averaged area contains black regions these regions will be
ignored by wxfalsecolor but will count as 0 in ximage or Photosphere. This
might account for wxfalsecolor reporting a larger value than Photosphere.
I really should document these things someday ...
Regards,
Thomas
···
On Mon, Dec 13, 2010 at 2:56 PM, Greg Ward <[email protected]> wrote:
Hi Thomas,
The -o option should give you original values, provided as you say
something hasn't happened in between to lose the calibration. I'm just
throwing out guesses. I have no idea why the results would disagree,
otherwise.
Cheers,
-Greg
> From: Thomas Bleicher <[email protected]>
> Date: December 13, 2010 11:14:16 AM PST
>
> Hi Greg.
>
> On Mon, Dec 13, 2010 at 12:19 PM, Greg Ward <[email protected]> > wrote:
> I am not familiar with wxfalsecolor. Is it possible that it is not
taking into account the EXPOSURE setting in the header?
>
> As I wrote, I just use "pvalue -o ..." to get the values from the image.
> It works fine with rendered images and test images I have created
> with pcomb. I have never used it on HDR images, though.
>
> I wanted to include a feature that checks the header information
> and warns if the images does not contain useable luminance values
> (after pcond has been used for example). I'm not sure if I understand
> these limitations myself correctly so I rely on the user to provide
> appropriate images.
>
> Regards,
> Thomas
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