A picture can be an effective means of compression. Sure, some visual sketches can be open to interpretation and vague, at best. But, some can also tell consistent stories (the ''same'' story, even when viewed by many people).

The best example that comes to mind is CharlesJosephMinard's chart depicting Napoleon's Russian campaign of 1812.  It is described in EdwardTufte's TheVisualDisplayOfQuantitativeInformation.  Once you understand how to read the diagram, it tells a brutal (and unambiguous) story.

-- ToddCoram

I take 'compression' to refer to reduction in 'information per square inch' in this context.