Function adjust

pattern/canvas.js:3099–3141

(img, options)

// function adjust(img, {hue:0, saturation:1.0, brightness:1.0, contrast:1.0})
function adjust(img, options) {
    /* Applies color adjustment filters to the image and returns the adjusted image.
     *  - hue        : the shift in hue (1.0 is 360 degrees on the color wheel).
     *  - saturation : the intensity of the colors (0.0 is a grayscale image).
     *  - brightness : the overall lightness or darkness (0.0 is a black image).
     *  - contrast   : the difference in brightness between regions.
     */
    var pixels = new Pixels(img);
    var adjust_hue = function(pixels, m) {
        pixels.map(function(p) {
            var hsb = _rgb2hsb(p[0]/255, p[1]/255, p[2]/255);
            var rgb = _hsb2rgb(Math.clamp((hsb[0] + m) % 1, 0, 1), hsb[1], hsb[2]);
            return [rgb[0]*255, rgb[1]*255, rgb[2]*255, p[3]]; 
        });
    }
    var adjust_saturation = function(pixels, m) {
        pixels.map(function(p) {
            var i = (0.3*p[0] + 0.59*p[1] + 0.11*p[2]) * (1-m); 
            return [p[0]*m + i, p[1]*m + i, p[2]*m + i, p[3]]; 
        });
    }
    var adjust_brightness = function(pixels, m) {
        pixels.map(function(p) {
            return [p[0] + m, p[1] + m, p[2] + m, p[3]]; 
        });
    }
    var adjust_contrast = function(pixels, m) {
        pixels.map(function(p) {
            return [(p[0]-128)*m + 128, (p[1]-128)*m + 128, (p[2]-128)*m + 128, p[3]]; 
        });
    }
    var o = options || {};
    if (o.hue !== undefined)
        adjust_hue(pixels, o.hue);
    if (o.saturation !== undefined && o.saturation != 1)
        adjust_saturation(pixels, o.saturation);
    if (o.brightness !== undefined && o.brightness != 1)
        adjust_brightness(pixels, 255 * (o.brightness-1));
    if (o.contrast !== undefined && o.contrast != 1)
        adjust_contrast(pixels, o.contrast);
    pixels.update();
    return pixels.image();
}

function desaturate(img) {
    /* Returns a grayscale version of the image.