FIGURE 1:

Contrast stretch and nonlinear (power-law) transformations. Original (A) and scaled (B–F) images of GFP-v-SNARE in yeast cells responding to mating pheromone. Autoscale contrast stretch (B) redistributes pixel values across the whole display range, without losing spatial information. Contrast can be stretched further (C) by setting an intermediate gray value (B, arrowhead) as white, but gray values in the range above the upper limit are clipped (C, asterisks), losing spatial information in the brightest regions. The nonlinear power-law transformation (D and E) redistributes gray values according to a logarithmic formula with exponent γ, resulting in increased contrast for a subset of gray values. Inversion (F) of an autoscaled image (as in B) displays dark values as light and vice versa without altering the distribution of pixel intensities.