The Mask module allows you to create a black mask that will be applied to the image. This function is useful if you want to cover a certain part of the image, which appears in the same place in all images. If possible, it is better to crop that part using the Preprocess module to reduce the input image.

The mask can also be applied to a heatmap if this option is ticked at the top panel.

Painting the mask

Painting of the mask works the same way as in Surface Detection module, there are two painting modes available.

Brush painting

Basic painting into the image by a brush of selected size. To change the brush size or switch between paint- and erase- mode, you can either use the sliders at the top, or you can use shortcuts, which can be found in the Help section under the ‘?’ symbol.

Polygons

When you choose the polygon mode, you left-click into the image to define vertices of the polygon, which are being connected with a line in the order you put them in. You can move existing vertices by clicking and dragging them, or use double-click to delete them. When you're satisfied with the shape, use right-click which joins the last vertex with the first one and fills in the polygon. Polygons work in the erase-mode as well.