DragonFly On-Line Manual Pages
pfshdrcalibrate(1) DragonFly General Commands Manual pfshdrcalibrate(1)
NAME
pfshdrcalibrate - Create an HDR image or calibrate a response curve
from a set of differently exposed images supplied in PFS stream.
SYNOPSIS
pfshdrcalibrate [--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
differently exposed images supplied in PFS stream.
When used with 8bit images, luminance in the output HDR image
corresponds 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
measurement 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
initialization 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
Recognition (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-
calibration 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 /
saturated areas. The black pixels are visible if all exposures
contain 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
channel 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
sample.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
problem 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 ALSO
pfsinhdrgen(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)