qoi | The “ Quite OK Image Format ” for fast , lossless image | Computer Vision library
kandi X-RAY | qoi Summary
kandi X-RAY | qoi Summary
Single-file MIT licensed library for C/C++. See qoi.h for the documentation and format specification. More info at
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QUESTION
For practice I've implemented the qoi specification in rust. In it there is a small hash function to store recently used pixels:
index_position = (r * 3 + g * 5 + b * 7 + a * 11) % 64
where r, g, b, and a are the red, green, blue and alpha channels respectively.
I assume this works as a hash because it creates a unique prime factorization for the numbers with the mod to limit the number of bytes. Anyways I implemented it naively in my code.
While looking at other implementations I came across this bit hack to optimize the hash calculation:
...ANSWER
Answered 2022-Apr-08 at 02:28If you think about the way the math works, you want this flipped order, because it means all the results from each of the "logical" multiplications cluster in the same byte. The highest byte in the first value multiplied by the lowest byte in the second produces a result in the highest byte. The lowest byte in the first value's product with the highest byte in the second value produces a result in the same highest byte, and the same goes for the intermediate bytes.
Yes, the 0x78...
and 0x03...
are also multiplied by each other, but they overflow way past the top of the value and are lost. Having the order "backwards" means the result of the multiplications we care about all ends up summed in the uppermost byte (the total shift of the results we want is always 56 bits, because the 56th bit offset value is multiplied by the 0th, the 40th by the 16th, the 16th by the 40th, and the 0th by the 56th), with the rest of the multiplications we don't want having their results either overflow (and being lost) or appearing in lower bytes (which we ignore). If you flipped the bytes in the second value, the 0x78 * 0x0B
(alpha value & multiplier) component would be lost to overflow, while the 0x12 * 0x03
(red value & multiplier) component wouldn't reach the target byte (every component we cared about would end up somewhat that wasn't the uppermost byte).
For a possibly more intuitive example, imagine doing the same work, but where all the bytes of one input except a single component are zero. If you multiply:
QUESTION
I have been trying to make the output of a wfe
model as tidy so I can easily incorporate it into ggplot and etc. This is a problem I've had with other packages and statistical models which are not included in broom.
So let's say I create a dataset like this: (taken from wfe
's file):
ANSWER
Answered 2021-Mar-29 at 12:37Here's a start at a tidy
method:
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