ASCOS satellite image correction tool - Documentation

This text describes the use of the ascos tool that implements a simple correction for atmosphere and shading influences in satellite images.

ASCOS stands for atmosphere and shading compensation of satellite images.

Compiling the program

ASCOS requires the CImg image processing library to be built and should be compilable on all platforms supported by the library.

Program options

the program offers the following command line options:

-i

Input Color image file to correct (required)

-d

Input DEM image file to use (required)

-o

Output image file name (required)

-16

Write output image with 16 bit per sample. The file format has to support this. Default: off.

-interactive

enable interactive mode (the image is displayed and parameters can be adjusted interactively). Default: off.

-b

The brightness adjustment for the image display in interactive mode. Default: 1.0.

-gamma

Gamma correction of the input color image. Default: 2.2.

-w

Correction weights for the atmosphere correction. Red, Green and Blue channel separated by colons. Default: 0.1:0.1:0.1.

-e

Atmosphere correction exponent. To be chosen between purely multiplicative (1) and additive (0) correction. Default: 1.0

-r

Reference height where no correction is applied. Unit: DEM image units. Values < 0 result in use of the maximum height in the image. Default: -1.

-z

Zero height level of the DEM image. Default: 32767.

-m

Height multiplier for the DEM image. Default: 1.0.

-resolution

Horizontal resolution of the color image. The resolution of the DEM is calculated from this. Unit: DEM image units. Default: 30.0.

-azimuth

Sun azimuth for the shading correction (Degrees). Default: 0.0.

-elevation

Sun elevation for the shading correction (Degrees). Default: 90.0.

-l

Correction weights for the shading correction. Red, Green and Blue channel separated by colons. Default: 0.1:0.1:0.1.

-h

show available options

Interactive operation

Without the -interactive option the program reads and processes the input image using the chosen options and writes the results to the output image. In interactive mode the algorithm parameters can be adjusted using the following controls:

• pressing the space key toggles the display of the DEM image/color image.
• pressing the z zooms the image to full size at the current mouse position. Pressing a second time switches back to full view. The image is always reset to unprocessed view in this case.
• pressing the a key runs the correction algorithm with the current parameters on the current view.
• pressing the x key resets to the unprocessed view.
• pressing cursor left/right adjusts the reference height or the correction exponent.
• pressing cursor up/down adjusts the or the correction Correction weights for atmosphere or shading correction.
• pressing page up/page down adjusts the display brightness.
• pressing the e key switches between reference height and exponent adjustment.
• pressing the r key switches to red channel atmosphere correction weight adjustment.
• pressing the g key switches to green channel atmosphere correction weight adjustment.
• pressing the b key switches to blue channel atmosphere correction weight adjustment.
• pressing the t key switches to red channel shading correction weight adjustment.
• pressing the h key switches to green channel shading correction weight adjustment.
• pressing the n key switches to blue channel shading correction weight adjustment.
• pressing the s key finishes interactive mode and processes the full image with current parameters.
• pressing the q key exits without saving.

Legal stuff

This program is licensed under the GNU GPL version 3. A copy of the license should be included in the program package. If you can not find it you can read it on http://www.gnu.org/licenses/gpl-3.0.html

Christoph Hormann, April 2006 - July 2007