English: An intuitive visual interpretation of a sinogram obtained by a Radon transform or tomography.

For each orientation, the tomographic projections of the shape are shown in the middle bar: each vertical position is the accumulated signal from a horizontal slice through the shape.

As the shape rotates, multiple such slices are taken, generating a sinogram on the right. The colors reveal what is going on: when the green line is aligned with the projection, all of its intensity gets concentrated so we obtain a bright green dot. The blue and red squares swap sides, and have either constant (aligned projection) or varying (diagonal projection) intensities.