This is a variant of the coastline_gen tool for generalizing glacier polygons. It is able to use coastline or other supplemental mask files to maintain connectivity or separation of the glaciers with other features during generalization.

Much of this program is highly experimental and not very robust. It will crash or produce nonsense results when called with the wrong options. Best to consider it just a demo for the moment.

glaciers_gen requires the CImg image processing library to be built and should be compilable on all platforms supported by the library. You need to download this library separately.
Copying CImg.h to the source directory is sufficient.

There are two versions of the program - glaciers_gen and glaciers_gen2, the latter is using a digital elevation file to take into account the relief shape.

Both versions have the following command line options:

• -i glaciers mask image file (required)

• -o Output image file name for the generalized glaciers mask (required)

• -f Input image file containing a mask to restrict generalization. Has to be the same size as main input (optional)

• -sf specifies how to interpret the fixed mask: 1: mask repels generalized features; -1: mask attracts generalized features.

• -rf influence radius of the fixed mask in pixels

• -l allows to set a bias in the outline position. Larger values move the coastline to the land. Default: 0.5

• -rs selection radius. Default: 4.0

• -rfs fixed mask search radius. Default: 5

• -rf fixed mask buffer radius. Default: 2.0

• -ro Radius values for opening steps erode:dilate:dilate:erode. Default: 2.2:2.2:1.2:1.2.

• -rc Radius values for closing steps dilate:erode:erode:dilate. Default: 2.2:2.2:1.2:1.2.

• -debug Generate a large number of image files from intermediate steps in the current directory for debugging. Default: off

• -h show available options

All image files are expected to be byte valued grayscale images with glacier pixel values > 0 and non-glacier pixel value 0. You can use any file format supported by CImg. When using GeoTiff files you will get some warnings that can be safely ignored. Note though that coordinate system information in any file is not transferred to the output. If necessary you have to do that yourself.

The program operates purely on the raster image and is unaware of the geographic coordinate system the data is supplied in. All parameters are specified in pixels as basic units.

glaciers_gen2 has additional parameters related to use of relief data. Elevation data is expected in the same grid as the source data.

Like coastline_gen glaciers_gen operates on raster images and you will normally have to use the following steps:

1. Rasterizing the glacier polygons, for example using gdal_rasterize.
2. Running glaciers_gen.
3. Vectorizing the resulting image, for example using potrace.

This program is licensed under the GNU GPL version 3.

Copyright 2013-2016 Christoph Hormann