Specific Data Import

Import of several other types of data is not automatic and it requires human intervention.

Graphics Formats

Importing data from image formats such as PNG, TIFF, JPEG or BMP is similar to import from raw/unknown file formats, only simpler.

It is simpler because the file structure is known and the file format is automatically detected. Hence the file type does need to be selected explicitly. However, the data interpretation is still unknown and must be specified manually. The Pixmap import dialog therefore resembles the Information tab of raw data import, requiring you to set the physical dimensions and value scale.

Note the physical dimensions suggested there are not obtained from the file, they are simply the last values used. Some SPM data format are based on an image format (typically, TIFF is used as the base) and contain the information about physical scales and units, albeit stored in a manufacturer-specific way. In this case a separate import module can be written for this particular format to load the files automatically with correctly scaled values.

See the reference section High-Depth Image Formats for the details of support for high-depth images and the possibility of using them for data representations.

Graph Curves

Simple two-column text files containing curve data can be imported as graph curves. In some cases, these files are recognized automatically. They can also be explicitly selected as ASCII graph curve files in the file open dialog, causing the import module to try harder to load the file as a graph data.

The import dialog shows a preview of the graph and permits to set the units and labels.

XYZ Data

Three-column text files containing XYZ data are imported by selecting the XYZ data files file type. Again, they can be recognized automatically but requesting this format explicitly makes the module to try harder to load the file as XYZ data.

The import dialogue displays the number of points and physical ranges of the data and permits setting the lateral and value units. The displayed ranges in physical units are updated according to the units you enter so you can immediately see if they they are correct.

Nano Measuring Machine XYZ Data

The Nano Measuring Machine data are sets of often huge XYZ files that would be difficult, if even possible to handle normally in Gwyddion. Therefore, they are directly rasterised to an image upon import. Select the main description file (.dsc) to open the data file set and set the import parameters.

Usually, the vertical size should be chosen as the number of profiles (i.e. number of data files). However, a larger resolution can be also useful. If you enable the Identical measures checkbox then the imported image will have square pixels. Only one resolution can be then entered – the other one is determined automatically.

On 64bit systems, the import module can currently handle up to 232 points per channel while the total number of data values is not limited. Note that reading the data points can take considerable time. Select only channels you are actually interested in to speed up the import process.