Create a Fast Linear Scaling Function
- CPU Optimized
- Reversible
- Rounding
There's a lot of alternatives, but I believe quick-scale provides a mix of features not found together in another package, including the ability to simply reverse the scale and define a strategy for when the range is zero.
npm install quick-scaleIn this basic example, we scale values from an unsigned 16-bit range (common in satellite imagery) to an unsigned 8-bit range (common in JPG and PNG files).
import { createScaleFunction } from "quick-scale";
// the [min, max] values for a 16-bit image
const old_range = [0, 65536];
// the [min, max] values for an 8-bit RGB image
const new_range = [0, 255];
const scale = createScaleFunction(old_range, new_range);
// apply this scale function to a bunch of numbers
scale(65535); // highest possible input value
255
scale(0); // lowest possible input value
0
scale(32767); // a value close to the middle
127.49805447470817We can round, flip and do more advanced things by passing in an options object:
const scale = createScaleFunction(old_range, new_range, {
// flip the scale, so higher and lower values are reversed
// the typical use case is if you want higher data values to appear
// darker in an RGB(A) image
flip: true,
// sometimes the difference between the min and max of a source range
// will be zero, like when an image transparency band is all 255
// if you'd like to provide a value to return in this case, set no_range_value
no_range_value: -99,
// if your input range is zero and you don't set no_range_value,
// then quick-scale will return the "highest", "lowest", or "middle" value of the new range
// the default is to return the highest value of the new range
no_range_value_strategy: "lowest",
// round the result
round: true
});
scale(65535);
0 // the highest value becomes the lowest because flip was set to true
scale(0);
255 // the lowest value becomes the highest because flip was set to true
scale(32767);
128 // rounded result