A thermal processor for thermally developing an image in an imaging material. In an embodiment, the integral one-piece leverage body has a handle, a pair of pivot pins projecting from opposed sides, a tongue projecting rearwardly, and a resilient biasing member projecting forwardly. A tall knuckle extends between the lateral support and the pair of lower lateral links. As a result, the diffusion distance is derived as the sum of dissimilarities over scales.