Say you have two ways to get a random seed, one way gives this, with "x" representing an independently chosen perfectly random bit, and zero representing a certain zero:
(1)
000xx00x00000xx00xx0000000000000x000x0x0x0x00x0000000xx0000000000x000x
xx0x0xxx00000000x00000x0x00000x0000000x0x0xx000000x00xx0xx0xxx00000000
00x0xx0000000x0xx000000xx00xx0x00000000x0000x00000x0x0x000x0x0x00xx000
0000x0000000x000000x00x000x0xx00x000x0xx0000x0000x000000x00x00xx000000
0000000x0x0000000x0x0000000000x00x0x00000xx00000x00xx0000000000x000000
00000000x00000xx00x00000x000x0000x00xx000000000x000000x00xx0000000x0xx
xx0xx00x000x0000x0x0000000x0x00000000x0x00x00xx00xx0000x00000000000000
0000000x0xxx0000000000
(2)
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
The first way provides very low-quality randomness (about 7/8 of the bits are zero), but provides much more security than the second way, because the second way has 64 random bits, and the first has 128 (count the number of "x").
The camera image is like the first, it has low quality randomness, but far more total randomness than the dice numbers.
The hash converts large volumes of low-quality randomness into a smaller amount (256 bits) of high quality randomness for your keys.
Alright but is there a way to actually quantify the amount of entropy an image has, to just make sure it's safe?
Because at least a dice roll can be quantified, because even a slightly deformed dice has 90% entropy, thats 2.3264662506 bits.
So any casino quality dice should be much better than that.
Don't use those particular images because you just published them
Of course not.