When Geocart becomes open-source, the distortion theme will no longer be a binary choice, but instead allow users to import databases. The top left pixel is no distortion, the bottom right pixel is maximum area and angular distortion. Angular distortion increases right, area distortion increases down. The larger the database, the more precision there is between min and max.
This is a simulation of what the defaults look like. (They are not exact, but they replicate the effect of obscuring to black if either area or angular distortion reaches maximum)
If the colors are instead mapped straight to the sRGB values, this is the database:
(Or, correspondingly, yellow/blue if the green and blue channels are switched)