Pixel-converters NPM

beta version

pixel-converters:

Simple conversion of pixels to RGB and RGBA, including automatic scaling and no data values.

features

immutable

core assumptions and constraints

An RGB pixel has these assumed properties:

array of 3 numbers between zero and 255
no data values represented by 0, 0, 0 or 255, 255, 255

An RGBA pixel has these assumed properties:

array of 4 numbers between zero and 255
the first 3 numbers are "data" values and the last value is an alpha tranparency value
an alpha value of 0 indicates that at least one of the data bands is "no data"
there may be a per-band no data value, but it is not required

A raw (unscaled) pixel value has these assumed properties:

between 1 and inifinity number of bands
number can be any valid number
no data value is the same for each band
there is no transparency channel/band

install

npm install pixel-converters

functions

convert_raw_to_rgb
convert_raw_to_rgba
convert_rgb_to_rgba
convert_rgba_to_rgb
create_nodata_rgb
create_nodata_rgba
has_no_data_value
hide_rgba
scale_number
scale_band_value
scale_band_value_holding_bottom
scale_band_value_holding_top
show_rgba

usage

convert_raw_to_rgb

You normally want to convert a raw pixel to an RGB 3-Band pixel when you are looking to save your pixel to a JPG file.

import { convert_raw_to_rgb } from "pixel-converters";

// example is a pixel in a Landsat 8 scene
const pixel = [5901];
const min = 0;
const max = 62196;
const old_no_data_value = 65536;
convert_raw_to_rgb(pixel, [min], [max], old_no_data_value);
[24, 24, 24]

// if you want to hold zero as the new no data value
// in other words, a no data pixel will be [0, 0, 0]
// because zero is taken, it will push all the scaled values up
convert_raw_to_rgb(pixel, [min], [max], old_no_data_value, 0);
[24, 24, 24]

// if you want your no data pixel to be pure white ([255, 255, 255])
// you can set the new no data value to 255
// this will push all the scaled pixel values down
convert_raw_to_rgb(pixel, [min], [max], old_no_data_value, 255);
[24, 24, 24]

convert_raw_to_rgba

You normally want to convert a raw pixel to an RGB 3-Band pixel when you are looking to save your pixel to a PNG file, HTML canvas, or another representation that supports an alpha band (transparency channel).

import { convert_raw_to_rgba } from "pixel-converters";

// using same pixel as above
convert_raw_to_rgba(pixel, [min], [max], old_no_data_value);
[24, 24, 24, 255]

// using same pixel as above, but reserving 0 for the new no data value
convert_raw_to_rgba(pixel, [min], [max], old_no_data_value, 0);
[24, 24, 24, 255]

// using same pixel as above, but reserving 255 for the new no data value
convert_raw_to_rgba(pixel, [min], [max], old_no_data_value, 255);
[24, 24, 24, 255]

pixel-converters v0.0.1