commit ddafaf26ea93791d949164061091bd41bd96cc4e
parent ae25790e98aecec6fea23cf4d4d040a541f7b8b4
Author: Vincent Forest <vincent.forest@meso-star.com>
Date: Fri, 5 Jun 2020 11:29:58 +0200
Update the man page
Diffstat:
1 file changed, 22 insertions(+), 23 deletions(-)
diff --git a/doc/htpp.1.txt b/doc/htpp.1.txt
@@ -32,7 +32,7 @@ DESCRIPTION
*htpp* post-processes a *htrdr-image*(5) and converts it to a PPM image [1] or
to a *gnuplot*(1) script. If _input_ is not defined, the *htrdr-image*(5) is
-read from standard input. Two post-processing procedures are provided: the
+read from standard input. Two post-processing procedures are provided: the
post-processing of the image colors (option *-i*), and the mapping of a given
pixel component onto a color ramp (option "*-m*). By default, *htpp*
post-processes the image color.
@@ -42,7 +42,7 @@ the third and the fifth components of each *htrdr-image*(5) pixel encode a
color with respect to the CIE 1931 XYZ color space. *htpp* first tone maps
these colors with the following filmic tone mapping operator [2]:
- out-color = f(in-color * exposure) / f(white-scale * exposure)
+ out-color = f(in-color * exposure) / f(white-value * exposure)
with:
@@ -57,11 +57,11 @@ with:
The _exposure_ term is an user-defined parameter provided as the _exposure_
image option. If not defined, a default _exposure_ of 1 is used. The
-_white-scale_ factor is either defined by the user through the _white_ image
-option or automatically computed as the luminance that is such that 99.5% of
-pixel radiances are less than _white-scale_. Once tone mapped, the pixels are
+_white-value_ is either defined by the user through the _white_ image option
+or automatically computed as the radiance that is such that 99.5% of pixel
+radiances are less than _white-value. Once tone mapped, the pixels are
transformed from the CIE 1931 XYZ color space into the sRGB linear color space
-before being gamma corrected. Finally, the resulting pixel components are
+before being gamma corrected. Finally, the resulting pixel components are
clamped to [0, 1] and encoded on 8-bits.
The mapping of a pixel component onto a color ramp is controlled by the *-m*
@@ -90,9 +90,10 @@ OPTIONS
**exposure**=__real__;;
Pixel exposure. By default its value is 1.
- **white**=__white-scale__;;
- Factor used to normalize input colors. If not defined, the white scale is
- automatically computed from the luminance of the _input_ image.
+ **white**=__radiance__;;
+ Radiance in the _input_ image that will represent the white color in
+ _output_. If not defined, the white value is automatically computed from
+ the radiance of the _input_ image.
*-m* <__sub-option__>[:<__sub-option__> ...]::
Map a pixel component to a regular color. Available sub options are:
@@ -115,12 +116,14 @@ OPTIONS
comportment.
**gnuplot**;;
- Write the _output_ as a gnuplot script rather than a PPM image. Once
- executed, the script generates a PNG image.
+ The _output_ image is formatted as a gnuplot script rather than a PPM
+ image. Once executed, the script generates a PNG image with an embedded
+ color ramp. Note that this script can be edited in order to adjust the
+ generated image to any requirements.
*-o* _output_::
- File where the PPM image is written. If not defined, write _output_ to
- standard output.
+ File where the result is written. If not defined, write _output_ to standard
+ output.
*-t* _threads-count_::
Hint on the number of threads to use. By default use as many threads as CPU
@@ -128,13 +131,9 @@ OPTIONS
*-v*::
Make *htpp* verbose. When used in post-processing of the pixel color (*-i*
- option), this option displays the __white-scale__ factor used to normalize
- the colors. In pixel component mapping mode (*-m* option), this option
- displays the color ramp and its associated values.
-
-*-w _white-scale_*::
- Factor used to normalize input colors. If not defined, _white-scale_ is
- automatically computed from the luminance of the _input_ image.
+ option), this option displays the radiance corresponding to the __white__
+ color in the output image. In pixel component mapping mode (*-m* option),
+ this option displays the color ramp and its associated values.
*--version*::
Display version information and exit.
@@ -149,10 +148,10 @@ already exists:
$ htpp -f -o img.ppm img.htrdr
Convert *img.htrdr* and visualise the resulting image by redirecting the
-standard output to the *feh*(1) image viewer. Use an _exposure_ of *0.5* and
-explicitly define the normalization factor to *0.0025*:
+standard output to the *feh*(1) image viewer. Use an _exposure_ of *0.2* and
+explicitly define the white color to *31.2* W/sr/m^2:
- $ htpp -i exposure=0.5:white=0.0025 img.htrdr | feh -
+ $ htpp -i exposure=0.2:white=31.2 img.htrdr | feh -
Use the *-m* option to map the values of the second pixel component clamped in
[0, 2] to the color ramp _magma_.
