Load an image, drawing, etc. to be measured.

Drawing & selecting
Draw lines by click and drag.
Hold Shift to snap lines to 45° angles.
Click on a line to select it; click empty space to deselect.
Hold Ctrl or Alt and click to add/remove from selection.
Press A to select all lines and arcs.
To move a line, select it then drag its endpoints or body.
Hold Ctrl or Alt while dragging to link endpoints to other lines.
Press Delete to remove selected lines or arcs.
Ctrl+Z / Ctrl+Y to undo / redo.

Calibration
Select a line and type a known real-world value, then press Enter.
All other lines update their lengths automatically.

Measure Angle
Click Measure Angle, then click two lines.
Move the mouse to choose sector and radius, click or press Enter to place.
Click a placed arc to select it; drag to reposition.
Press Escape or click the button again to cancel.

Draw Grid
Click Draw Grid, then click two lines to define the grid edges.
Set Cross and Along cell counts before or after selecting.
Drag the endpoint circles to adjust the grid shape live.
Toggle between Affine Spacing (even) and 2VP Spacing (perspective-correct).
The spacing button turns red if the quad is concave (2VP mode only).
Press Enter to commit the grid lines, Escape to cancel.
Press the button again to cancel and clear the selection.

View
Scroll to zoom  |  + / - keys to zoom.
Arrow keys or middle-mouse drag to pan.
↺ / ↻ buttons to rotate 45°  |  Reset View to re-center.

Save outputs PNGs, SVGs, and CSV.