htrdr 0.8.1



htrdr-image - two dimensional image format


The htrdr-image is a raw image file format where data are stored in plain text. Characters after the # character are considered as comments and are thus ignored as well as empty lines. The first valid line stores 2 unsigned integers that represent the image definition, i.e. the number of pixels per line and per column. Then each line stores 8 floating point components per pixel.

Pixels are sorted line by line, with the origin defined at the top left corner of the image. With an image definition of N by M pixels, with N the number of pixels per line and M the overall number of lines in the image, the first N pixels correspond to the pixels of the top line of the image, the following N pixels are the pixels of the second line and so on.

The htpp(1) program can be used to convert an htrdr-image into a regular PPM image [1]. Note that the nature and unit of the data stored in an htrdr-image is not determined by the file format itself. Refer to the program that generates the image for a full description of the data it contains.


<htrdr-image>    ::= <definition>
                   [ <pixel> ... ]

<definition>     ::= <width> <height>
<width>          ::= INTEGER
<height>         ::= INTEGER

<pixel>          ::= <pixel-sw>
                   | <pixel-lw>

<pixel-sw>       ::= <X> <Y> <Z> <time>
<pixel-lw>       ::= <temperature> <radiance> 0 0 <time>

<X>              ::= <estimate>
<Y>              ::= <estimate>
<Z>              ::= <estimate>
<time>           ::= <estimate>
<temperature>    ::= <estimate>
<radiance>       ::= <estimate>

<estimate>       ::= <expected-value> <standard-error>
<expected-value> ::= REAL
<standard-error> ::= REAL


The following output was produced by htrdr(1) invoked to render an image of 800 by 600 pixels. Note that actually the comments and blank lines were not necessarily written by htrdr(1); they are used here only to help the reader understand the data layout. The comment after each pixel gives the two-dimensional index of the pixel in the image: the first and second integer is the index of the line and the column of the pixel in the image, respectively.

800 600 # Image definition

# Pixels of the 1st line
2.55e-4 2.90e-5 3.75e-4 4.48e-5 3.20e-4 3.16e-5 306.484 259.723 # (1,1)
2.95e-4 3.37e-5 3.39e-4 4.16e-5 3.38e-4 4.60e-5 18.3633 2.66317 # (2,1)
3.76e-4 5.43e-5 3.13e-4 3.48e-5 3.38e-4 3.32e-5 19.6252 2.67015 # (3,1)
7.13e-4 1.14e-4 7.66e-4 1.35e-4 7.97e-4 1.26e-4 119.820 93.7820 # (799,1)
6.59e-4 1.14e-4 7.47e-4 1.41e-4 4.39e-4 7.33e-5 24.8655 2.46348 # (800,1)

# Pixels of the 2nd line
3.33e-4 6.02e-5 4.21e-4 7.66e-5 3.44e-4 3.81e-5 19.4580 2.50692 # (1,2)
3.50e-4 4.93e-5 3.23e-4 2.52e-5 3.03e-4 2.42e-5 102.566 81.2936 # (2,2)
2.72e-4 4.69e-5 3.41e-4 4.12e-5 2.52e-4 2.06e-5 25.5801 5.37736 # (3,2)
7.52e-4 1.31e-4 8.91e-4 1.84e-4 5.48e-4 1.30e-4 46.5418 12.4728 # (799,2)
6.82e-4 1.42e-4 6.61e-4 7.85e-5 4.44e-4 5.99e-5 59.8728 32.1468 # (800,2)


# Pixels of the 600th line
2.69e-4 7.44e-5 2.31e-4 2.56e-5 1.95e-4 2.30e-5 43.8242 15.0047 # (1,600)
4.32e-4 1.25e-4 2.22e-4 2.22e-5 2.04e-4 2.60e-5 25.5498 1.73942 # (2,600)
2.78e-4 5.81e-5 2.75e-4 4.99e-5 2.17e-4 3.30e-5 38.4448 7.16199 # (3,600)
3.54e-4 4.32e-5 3.07e-4 3.80e-5 2.38e-4 2.49e-5 102.893 36.9865 # (799,600)
3.07e-4 2.61e-5 4.60e-4 1.13e-4 2.69e-4 4.29e-5 42.75070 11.913 # (800,600)


1. Portable PixMap -


htpp(1), htrdr(1)