image-sequencer/src/modules/Contrast/Contrast.js

var _ = require('lodash');

module.exports = exports = function(pixels, contrast) {
    let oldpix = _.cloneDeep(pixels);
    contrast = Number(contrast)
    if (contrast < -100) contrast = -100;
    if (contrast > 100) contrast = 100;
    contrast = (100.0 + contrast) / 100.0;
    contrast *= contrast;

    for (let i = 0; i < pixels.shape[0]; i++) {
        for (let j = 0; j < pixels.shape[1]; j++) {
            var r = oldpix.get(i, j, 0) / 255.0;
            r -= 0.5;
            r *= contrast;
            r += 0.5;
            r *= 255;
            if (r < 0) r = 0;
            if (r > 255) r = 255;


            var g = oldpix.get(i, j, 1) / 255.0;
            g -= 0.5;
            g *= contrast;
            g += 0.5;
            g *= 255;
            if (g < 0) g = 0;
            if (g > 255) g = 255;


            var b = oldpix.get(i, j, 2) / 255.0;
            b -= 0.5;
            b *= contrast;
            b += 0.5;
            b *= 255;
            if (b < 0) b = 0;
            if (b > 255) b = 255;


            pixels.set(i, j, 0, r);
            pixels.set(i, j, 1, g);
            pixels.set(i, j, 2, b);

        }
    }
    return pixels;
}