Basic workflow#

The usual GraphX sequence is image → calibration → dataset → points → check → optional trendline → export or save.

Open the source image#

Choose an image with readable axis values and enough resolution to place points accurately. A curve that is distinguishable from its background and nearby lines is especially helpful for Trace curve. The source does not need to be perfectly square or level: GraphX supports rotated and sheared plots, and Perspective calibration for photographs.

Choose the calibration method#

Use Fast for ordinary screenshots, scans, and exported plots where affine correction is sufficient. Use Perspective when a photograph has projective distortion, such as opposite plot edges appearing to converge. Select Linear or Logarithmic independently for each axis.

See Calibration overview, Fast calibration, Perspective calibration, and Logarithmic axes for the method-specific guidance.

Calibrate#

With Fast calibration, place the X1, X2, Y1, and Y2 reference positions and enter their graph values. With Perspective calibration, set the four plot corners, refine them if necessary, then enter the edge values. Check that reference positions and values match the source before digitising.

Create or select a dataset#

Points are added to the active dataset. Create separate datasets for separate curves or series, and use their colours to distinguish them on the graph. The active dataset can be renamed and its numerical precision adjusted from the Datasets area and Data points drawer.

Digitise the curve#

Use Add/edit points when you want to place points manually or correct individual positions. Use Trace curve when a curve can be followed from a selected seed; inspect its preview and output markers before adding the resulting points. You can correct points afterwards in either case.

Check the data#

Review point positions, calibrated values, the active dataset, and the chosen precision before exporting. If calibration changes, GraphX recalculates existing point coordinates from their saved positions on the source image, so recheck the resulting values and any extrapolation markers.

Optional trendline#

After digitising, add a trendline for a dataset if a fitted model is useful. Its fit and display ranges can be reviewed independently of the original measured points.

Export#

Use Export for CSV, PDF, or JPEG output. Copy data copies the active dataset as tab-separated values for pasting into another tool. Checked datasets are included where that export supports them.

Save the project#

Use Save project to keep an editable .graphx file with the source image, calibration, datasets, points, settings, and project notes. Reopen it later with Open project. Saving a project preserves work; exporting creates a separate result for sharing or analysis.