Here is a study illustration I drew up that is being used in a Processing sketch. The illustration was done completely in Inkscape 0.48 using the Calligraph Tool with the Trace setting enabled. I drew background shapes using linear and radial gradients in grays and used those to get my ink sketchy look. I then loaded it into my Processing sketch and disabled the style of the image so I can then manipulate the various elements within the svg file. So far in playing around with it I have background colours of the background, vessel, and lid of the vessel change over a period of time using some random numbers. This is a rough test and I am working on another more refined illustration.

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ImageShack.usThese two screen captures show two colour change stages.