pfshdrcalibrate(1)pfshdrcalibrate(1)NAMEpfshdrcalibrate - Create an HDR image or calibrate a response curve
from a set of differently exposed images supplied in PFS stream.
SYNOPSISpfshdrcalibrate [--response <type>] [--calibration <type>] [--gauss
<val>] [--response-file <filename.m>] [--save-response <filename.m>]
[--multiplier <val>] [--bpp <val>] [--luminance] [--samples <val>]
[--help] [--verbose]
DESCRIPTION
Create an HDR image or calibrate a response curve from a set of differ‐
ently exposed images supplied in PFS stream.
When used with 8bit images, luminance in the output HDR image corre‐
sponds to real world values in [cd/m^2] provided that hdrgen script
contained correct information on exposure time, aperture and iso speed.
Note that sometimes ISO speed indicated by camera does not correspond
to standard (ISO-100 is in fact ISO-125).
The accuracy of absolute calibration has not been thoroughly tested
with different camera models, however one can expect the relative mea‐
surement error below 8%. Use pfsabsolute in case of systematic error.
OPTIONS--response <type>, -r <type>
Allows to choose from predefined response curves. This can be
used either to apply this response or use it as an initializa‐
tion for automatic self-calibration. Predefined response curves
are: "linear", "gamma", "log". Default is "linear".
--calibration <type>, -c <type>
Type of automatic self-calibration method used for recovery of
the response curve. Accepted types include: "none", "robertson",
"mitsunaga". Default is "robertson". In case "none" is chosen, a
predefined response will be used, without self-calibration. More
infomation on the algorithms can be found in:
M.A. Robertson, S. Borman and R.L. Stevenson
Dynamic range improvement through multiple exposures
In: Proc. of International Conference on Image Processing 1999
(ICIP 99), pp 159-163 vol.3
and
T. Mitsunaga and S. K. Nayar
Radiometric Self Calibration
In: Proc on IEEE Conf. on Computer Vision and Pattern Recogni‐
tion (CVPR'99). Volume 1, p. 1374
--gauss <val>, -g <val>
Sigma value for the Gaussian used as a weighting function.
Applies to Robertson02 algorithm. Default value: 16.0f
--response-file <filename.m>, -f <filename.m>
Use response curve saved in the matlab format file. Turns off
automatic self-calibration. Uses Robertson02 model to apply the
response curve.
--save-response <filename.m>, -s <filename.m>
Saves the response curve calculated during automatic self-cali‐
bration stage in a matlab format file. Can be later reused for
set of images captured with given camera. Also works fine for
plotting with gnuplot.
--multiplier <val>, -m <val>
Input multiplier value. Can be used to manipulate the range of
source exposures. Default value is 256 since LDR images are by
default scaled to 0..1.
--bpp <val>, -b <val>
Number of bits per pixel in input data from the camera. Default
value is 8.
--samples <val>, -p <val>
Number of sample pixels used in inverse response computations in
Mitsunaga algorithm. Default is 50000.
--fix-saturated, -x
Use this option if you see black pixels in overexposed / satu‐
rated areas. The black pixels are visible if all exposures con‐
tain pixel values that are outside reliable range (are under- or
over-exposed). This flag gives non-zero weight for the brightest
and the darkest pixels, thus avoiding zero-weighted pixels. Note
that the calculated luminance values for these pixels are not
reliable.
--luminance, -Y
Recovery of response curve will be performed for luminance chan‐
nel only.
--verbose
Print additional information during program execution.
--help
Print list of commandline options.
EXAMPLES
pfsinhdrgen sample.hdrgen | pfshdrcalibrate-v -s response.m
Recover the response curve from set of exposures defined in sam‐
ple.hdrgen and save it to response.m file. To view the response
curve, run gnuplot and write 'plot "response.m"'.
pfsinhdrgen sample.hdrgen | pfshdrcalibrate-x -f response.m | pfsview
Create an HDR image from exposures defined in sample.hdrgen
using the response curve "response.m" and view it. Fix the prob‐
lem with black values given to overexposed pixels.
pfsinhdrgen sample.hdrgen | pfshdrcalibrate | pfsview
Create an HDR image from exposures defined in sample.hdrgen
using the default self-calibration method and view it.
pfsinhdrgen sample_dcraw.hdrgen | pfshdrcalibrate-b 16 -r linear -c
none | pfsview
Given that the script sample_dcraw.hdrgen refers to camera RAW
files (see pfsindcraw), this example will generate an HDR image
assuming a linear response.
pfsinhdrgen sample.hdrgen | pfshdrcalibrate | pfsview
Create an HDR image from exposures defined in sample.hdrgen
using the default self-calibration method and view it.
pfsinhdrgen sample.hdrgen | pfshdrcalibrate-c mitsunaga -samples
100000 | pfsglview
Create an HDR image from exposures defined in sample.hdrgen
using the mitsunaga self-calibration method with 100000 samples
and view it in pfsglview.
SEE ALSOpfsinhdrgen(1)jpeg2hdrgen(1)pfsview(1)pfsindcraw(1)pfsabsolute(1)pfsglview(1)BUGS
Please report bugs and comments on implementation to Grzegorz Krawczyk
<gkrawczyk@users.sourceforge.net>.
pfshdrcalibrate(1)
