Getting Started

The tool has three main areas. The left sidebar contains tool buttons: Select (V), Measure Angle (M), and Pan View (Space). The center is your canvas where you place protractors and draw measurements. The right panel shows controls for protractors, images, and statistics. At the top center, you'll find undo/redo buttons with a history counter showing how many steps you can undo.

Click the '+' button in the Protractor panel on the right side. A protractor appears at the canvas center. Click and drag the protractor to move it anywhere on the canvas. You can also enter exact X and Y coordinates in the panel for precise positioning. The protractor displays degree markings from 0° to 180° on both sides.

Make sure the Select tool (V) is active in the left toolbar. Click on a protractor to select it - you'll see a blue outline. Drag it to move. Use the rotation handle (circular arrow icon) to rotate the protractor, or enter an exact rotation angle in the panel. You can also scale the protractor using the size slider or by entering a scale value.

Select a protractor, then click the Measure Angle tool (M) in the left toolbar. Move your mouse from the protractor center - you'll see a preview ray following your cursor. Click to place the first ray. Move your mouse again and click to place a second ray. The angle between the two rays appears automatically with a label showing the measurement in degrees.

Each angle measurement shows the inner angle by default (the smaller angle between two rays). Click on the angle value to toggle between inner and outer angles. The outer angle is 360° minus the inner angle. You can change the unit from degrees to radians in the Statistics panel. Adjust decimal precision (0-4 places) to match your needs.

Select a protractor and use the panel controls to change its color - click the color picker to choose from a palette. Adjust the opacity slider to make the protractor semi-transparent, useful when overlaying on images. Change the size using the scale slider. Each protractor can have different settings, allowing you to color-code multiple measurements.

After placing rays, switch back to Select tool (V) to modify them. Click a ray to select it - it highlights in a brighter color. You can change the ray's color in the panel. To delete a ray, select it and press Delete or Backspace, or use the delete button in the panel. Rays are always drawn from the protractor's center point.

Click the Export button in the top toolbar. Choose JSON to save your complete workspace - this includes all protractors, rays, measurements, and settings. You can reload this file later to continue working. Choose CSV to export just the measurement data in a spreadsheet format. Choose PNG or JPEG to save an image of your canvas at 1x, 2x, or 4x resolution.