How Digital Images Really Work

We take digital images for granted these days—hell, you're looking at dozens right now. But when you stop and think about how the 3D world can be represented so neatly by 1D data stored on a hard drive, it's really utterly amazing.

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In this video, Mike Pound explains how digital images really work. They're perhaps not as fluffy and user-friendly as you might think, at least at the computer-level: they're not neatly stored as a 2D matrix, but instead as a long list that goes on and on and on and on... Anyway, over to Mike to explain how all these images are really stored. [Computerphile]

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DISCUSSION

That's not how images are stored on disk. That's how bitmap images are stored in the video memory. Once upon a time (so like >30 years ago) those two things were the same (device-dependent bitmaps) or at least close to each other (device independent bitmaps), but nowadays images are stored

1. in a compressed format on a disk (like in JPEG or PNGs) which use a completely different storage format and add several layers of coding on top of the bitmap representation.

2. in vector formats (like SVG, WMF, etc) which have practically nothing to do with bitmaps (less preview thumbnails encoded optionally in some of them), because their concept is completely different from the latter.

Also, statements like "at the computer-level: they're not neatly stored as a 2D matrix" make no sense, because since computer memory is linear and computer storage is either linear (at the file level) or block based (at the sector/cluster/etc level), there's no way to store _anything_ in a 2D matrix in computer systems - at least not in the strict term of the word, and not on the logical level.

On the other side a 2D matrix (or any nD matrix where n>0) structure can be easily represented and accessed both in computer memory and on storage, using offset-based indexed access.