Creating a png file

Geometries for the model domain within SeidarT are initiated with a PNG image. The program identifies unique RGB values, setting material properties for each. For example, if you wanted to define a geometry with ice overlying bedrock, you would create a .png image that is one color for the ice and another for the rock below. Everyone has their preferences to generate images but GIMP or Inkscape provide free and open software that are more than sufficient.

Note

When creating a PNG, anti-aliasing must be turned off to avoid color boundary gradients. When building the project file from a PNG, if antialiasing isn’t turned off, this will be evident in the material list.

Building images in Inkscape has some advantages other than being free. It is a robust graphics application that provides a lot of control. Saving a .svg to pdf allows the user to change the number of pixels and the spatial resolution of the image quite easily, but keep in mind that the size of all features within the image will increase/decrease accordingly (i.e. 1px wide will become 2px wide when doubling the domain size. With ghostscript, the command

gs -q -dBATCH -dNOPAUSE -sDEVICE=png16m -sOutputFile=<file> -r96 <input_file>

will generate a PNG file from a PDF. The resolution -r can be varied to change the pixels. In Inkscape, the image pixels can be set in Document Properties. When saving the SVG as PDF, you will be prompted with options, and the value for Resolution for rasterization (dpi): will determine - in order to get the same pixel setting that you set in Inkscape - the value for the -r (resolution) option above. In the above code block, the default rasterization of 96 was used so if you want to double the resolution, just double this number (i.e. -r192).