Histogram Tool
The Histogram Tool runs r.stats over a raster (optionally within a drawn bounding box) and displays the value distribution as an interactive bar chart.
Opening the tool
Click the histogram toolbar button (the bar-chart icon with a curved overlay) to open the Histogram Tool panel.
Steps
- Select a raster from the Input raster dropdown
- Set nsteps — the number of histogram bins (default 255)
- Set null value — the string used to represent no-data (default
*) - Optionally click Draw Box and drag a bounding box on the map to restrict the analysis
- Click Run
Controls
| Button | Action |
|---|---|
| Draw Box | Enter bounding-box drawing mode on the map |
| Clear Box | Remove the drawn bounding box |
| Run | Execute r.stats and render the histogram |
| ↺ Re-run (chart toolbar) | Re-run with current settings |
Bounding box
The drawn box constrains the statistics to the selected area. It is drawn as a rectangle overlay on the Cesium globe and remains visible until cleared. The box is independent of the GRASS computational region.
Chart
The histogram chart shows value bins on the X axis and count/area on the Y axis. Zoom with scroll and pan by dragging (Chart.js zoom plugin).
Session persistence
The active raster, nsteps, null value, bounding box, and chart result are saved in the workspace autosave.