Ubuntu Manpage: pfshdrcalibrate - Create an HDR image or calibrate a response curve from a set of differently exposed

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>]
       [--saturation-offset <val>] [--deghosting <val>] [--noise-parameters <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.

       The merging of multiple exposures is done in a noise-optimal manner, as explained in the paper:

              Hanji, Param, Fangcheng Zhong, and Rafal K. Mantiuk.
              “Noise-Aware Merging of High Dynamic Range Image Stacks without Camera Calibration.”
              In Advances in Image Manipulation (ECCV Workshop), 2020. http://arxiv.org/abs/2009.07975.

OPTIONS

--response <type>, -r <type>

Allows one 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". This option can be used only with Robertson
method.

--calibration <type>, -c <type>

Type of automatic self-calibration method used for recovery of the response curve and/or type of
method used for HDR merging. Accepted types include: "robertson", "mitsunaga". "robertson" is the
default and recommended algorithm (see commends in the Bugs section below). More information 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 (in the range 0-1). Applies to
Robertson02 algorithm. Default value: 0.2

--response-file <filename.m>, -f <filename.m>

Use response curve saved in the matlab format file. Turns off automatic self-calibration. Uses
Robertson02 or Mitsunaga99 model to apply the response curve (see -c option).

--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 for
Robertson method is 256 since LDR images are by default scaled to 0..1. This value is set to 1.0
for Mitsunaga method.

--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 samples used during the self-calibration in Mitsunaga algorithm. Default is 50000.

--saturation-offset <val>, -o <val>

Pixels are considered saturated if their value exceeds max_val * (1-sat_offset), where max_val is
the maximum pixel value (e.g. 255 or 65535) and sat_offset is the percentage of the maximum value.
The default value is 0.01. Use this if you can see banding or wrong colors in the regions in which
one of the exposures is saturated.

--noise-parameters <val>, -n <val>

Measured noise parameters for the specific camera used. This can be specified in 2 ways. The first
is using a comma separated list of 5 values (3 color coefficients, std_readout and std_adc).
Alternatively, some presets have been defined and can be used by specifying the camera name.
Cameras currently supported: SonyA7r1, CanonT1, SonyA7r3

--deghosting, -d [<val>]

EXPERIMENTAL. Try to use a simple rejection criterion to reduce ghosting artifacts due to
movement. If the option is specified, the pixel values that <val> standard deviations of the noise
away from the reference exposure are rejected. When the option is missing from the argument list,
the deghosting is disabled. When the option is specified without any value, 2 standard deviations
are used.

--luminance, -Y

Recovery of response curve will be performed for luminance channel only.

--verbose

Print additional information during program execution.
--help

Print list of command line options.

EXAMPLES

       pfsinme *.JPG | pfshdrcalibrate -v -s response.m | pfsview
              Recover  the  response  curve  from  set of all JPEG files in the current directory and save it to
              response.m file. To view the response curve, use pfsplotresponse command.
       pfsinme *.CR2 | pfssize  --maxx 1200 | pfshdrcalibrate -r linear -v --bpp 16 | pfsout result.exr
              Read Camera RAW images (from Canon), resize them so that the image width is  equal  or  less  1200
              pixels, merge them into an HDR image using all 16 bits and save as an Open EXR image.
       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 -s resp_mitsunaga.m >/dev/null
              Create  an  HDR image from exposures defined in sample.hdrgen using the mitsunaga self-calibration
              method with 100000 samples and save it to "resp_mitsunaga.m".

BUGS