3.3.5. Import Images

TODO: Introduction and image

3.3.5.1. Import geologic images

GIFtools allows one to import geologic maps in order to populate models and ultimately constrain inversions. Plan-view images can be imported in current versions. In the near future, cross-section images will be accessed through the same menu pipeline.

Use the main project menu: Import → Image → Plan-view

../../../_images/importImage.png

Along with the image file, a world file is required to georectify the image. A legend file to specify the RGB values for each geology unit can be imported when importing the image or either imported or created after image importation.

NOTE: Images with distinct colour combinations and no text will perform much better when discretizing models. Below is an example:

../../../_images/planViewImageEx.png

3.3.5.1.1. World file format

The world file has been specified by Esri (.tfw file). It is a plain text file with the following lines. GIFtools will recognize rotations given in this file.

  • Line 1: pixel size in the Easting direction in pixels

  • Line 2: rotation about Northing axis

  • Line 3: rotation about Easting axis

  • Line 4: pixel size in the Northing direction in pixels, (almost always negative)

  • Line 5: Easting coordinate of the center of the upper left pixel

  • Line 6: Northing coordinate of the center of the upper left pixel

Below is an example:

../../../_images/worldFile.png

3.3.5.1.2. Legend file format

The legend file will be an XYZ or CSV with a header. The important headers are the geology unit (integer), Red, Green, and Blue values (0-255) contained within image. Comments are denoted by “!” or “//”. Below is an example of 8 units (0 being background white) for the image above.

../../../_images/legendFile.png

To create a legend file, load the image and use the menu:

Plan-view image → Legend → Create → Table view