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by nayuki
869 days ago
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I'll analyze PNG for comparison. The largest width and height is 2147483647 (2^31 - 1). Using the pHYs chunk (physical pixel dimensions), the lowest density we can specify is 1 pixel per metre. So, 2 billion metres (2 gigametres) is somewhat bigger than the diameter of the sun at 1.39 Gm. https://en.wikipedia.org/wiki/Orders_of_magnitude_(length)#g... Using the sCAL chunk (physical scale) would allow extremely large dimensions because it uses ASCII floating-point. |
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AFAIK sCAL is more about the image's subject, not the image itself. A 1:10,000,000 scale world map would be < 10 m wide according to pHYs, but it will be ~40,000 km wide according to sCAL.