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Comment by mehrdadn | Hacker News Reader

Not really. Some RAWs from some cameras do compress, but not others. (Not sure why; maybe it's already pre-compressed.) As an example, I tried just compressing a random 30MB RAW from my camera (just a photo of jeans, nothing particularly unusual) with 7z on Ultra compression, and it saved—guess what—a whopping 2.2% of its size.

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7z is a generic lossless compressor. These algorithms tend to specialize in exact repeating patterns in sequences. Good for english prose, but images tend to have non-exact patterns in two dimension. A dedicated algorithm like FLIF will be much better at picking those up. I would expect an order of magnitude difference in performance between 7z and FLIF.

For the curious: the way these non-exact pattern compressors work is by subtracting out the predicted pattern and then storing the remaining signal, which will be smaller numbers and therefore take less bits to store.

What is your camera? Multiply your sensor size by the bit depth, and I suspect you’ll have more than 30mb.

Also image compressors like FLIF vastly outperform general compressors on images.

Some RAW formats are pre-compressed, usually with very simple (hence fast) algorithms, and some aren't even lossless (Sony ARW). It's often possible to further compress them with specialized tools.

Disclosure: I'm the author of PackRAW, a tool that does exactly that (https://encode.su/threads/2762-PackRAW)

The RAW format is probably using e.g zlib for compression internally. You can check by calculating how many bytes in total a truly raw image is: 12-16 bits (1.5-2 byte) per pixel.

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