1hdrprep(3)                                                          hdrprep(3)
2
3
4

NAME

6       hdrprep - Align sequences of exposure-bracketed digital photographs and
7       fix EXIF header.
8

SYNOPSIS

10       [-h|--help]   [-v|--verbose]   [-a|--align]   [-r|--redo]   [-e|--exif]
11       [-d|--directory  dir] [-k|--keep] [-m|--mc percent] [-q|--quality qual]
12       images
13
14

DESCRIPTION

16       Most HDR software currently available is not capable  of  automatically
17       registering  the  frames  of  a  hand-held  image  sequence and assumes
18       instead that a heavy-duty tripod is used. Software that is  capable  of
19       auto-alignment might fail if the exposures encountered are too extreme,
20       i.e. some frame are too much over- or under-exposed.
21
22
23       Another potential problem with HDR generation is that the software  can
24       not  always  retrieve  the  exposure  information from the images' EXIF
25       header, as is required for response curve calibration. This is  usually
26       caused  by incorrect implementation of the EXIF standard and the use of
27       proprietary tags.
28
29
30       hdrprep was written to resolve those  problems.  The  process  involves
31       three steps:
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33
34              1.  Run  ALE to compute the transformation necessary to register
35              the frames;
36              2. Run ImageMagick to shift and crop the frames  using  the  ALE
37              results;
38              3. Optionally fix the EXIF header.
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40
41       The Anti-Lamenessing Engine, ALE, was designed to combine images of the
42       same scene and similar exposure in order to increase  colour  fidelity,
43       reduce  aliasing  and  artifacts, and generally increase the quality of
44       the image. It features sophisticated  alignment  algorithms  which  may
45       also  be  used  to prepare exposure-bracketed sequences for HDR genera‐
46       tion.
47
48
49       While ALE can not itself save the aligned images,  this  is  done  with
50       ImageMagick commands.
51
52
53       Optionally,  the  Perl  module Image::ExifTool is used to fix corrupted
54       EXIF tags.
55

OPTIONS

57       The principal options are -a, -r and -e, of which at least one must  be
58       given on the command line. While -a and -r are mutually exclusive, both
59       may be run in combination with -e, which may also be run separately.
60
61
62       -a|--align
63              Run ALE to  compute  the  required  transformations,  then  call
64              ImageMagick  to  shift,  crop and re-save the images. Currently,
65              the only supported transformation is  translation  in  x  and  y
66              direction. This corresponds to steps 1 and 2.
67
68
69       -r|--redo
70              Do  not run ALE, only call ImageMagick. This requires a previous
71              run with -a to the same directory. See -d option  below.  Corre‐
72              sponds to step 2.
73
74
75       -e|--exif
76              Fix  EXIF  headers with ExifTool. May be run in combination with
77              -a and -r or by itself. Either way, it only operates  on  copies
78              and  never on the originals of your images. Step 3 from Descrip‐
79              tion.
80
81
82       -d|--directory dir
83              Save results to directory dir.  Defaults  to  ./aligned  if  not
84              qualified.
85
86
87       -k|--keep dir
88              Don't remove intermediate images created by ALE.
89
90
91       -q|--quality qual
92              Save newly created images with quality setting qual. The default
93              is set to 80.
94
95
96       -m|--mc percent
97              Sample percent of pixels for image alignment. Default is 10%.
98
99
100       -h|--help
101              Display help and usage information and exit.
102
103
104       -v|--verbose
105              Print additional output.
106

EXAMPLES

108       To register files dscn602?.jpg. The resulting JPEG images will be saved
109       in  directory  ./test1  with  a quality setting of 90. The directory is
110       created if it doesn't exist.
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112
113              hdrprep --quality 90 --dir test1 --align dscn602?.jpg
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115
116       Same as above, but results are saved with a lower quality.  The  trans‐
117       formation  files  are re-used, so ALE not run. This requires a previous
118       run with -a using the same directory.
119
120
121              hdrprep -q 60 -d test1 --redo dscn602?.jpg
122
123
124       Same as above, but this time also fix the EXIF headers and sample  more
125       pixels for alignment.
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127
128              hdrprep -q 60 -d test1 --redo --exif --mc 20 dscn602?.jpg
129
130
131       Only  fix the EXIF headers. If ./test2 doesn't exist or doesn't contain
132       files with names identical to those provided on the  command  line,  it
133       will be created and the files copied into it.
134
135
136              hdrprep -d test2 --exif dscn60[3|4]?.jpg
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AUTHOR

142       Axel Jacobs. Send feedback to <axel at luxal dot eu>.
143

REFERENCES

145       Perl   http://www.perl.org
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147
148       Anti-Lamenessing Engine (ALE)
149              http://auricle.dyndns.org/ALE/
150
151
152       Image::ExifTool
153              http://www.sno.phy.queensu.ca/~phil/exiftool/ExifTool.html
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155
156       ImageMagick
157              http://www.imagemagick.org
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159
160       PerlMagick
161              http://search.cpan.org/dist/PerlMagick/Magick.pm,
162              http://www.imagemagick.org/script/perl-magick.php
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164
165       WebHDR http://luminance.londonmet.ac.uk/webhdr
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168
169Axel Jacobs                          0.1.2                          hdrprep(3)