image-sequencer/src/modules/Average/Module.js

/*
* Average all pixel colors
*/
module.exports = function Average(options, UI) {

    var output;

    options.step.metadata = options.step.metadata || {};

    function draw(input, callback, progressObj) {

        progressObj.stop(true);
        progressObj.overrideFlag = true;

        var step = this;

        // do the averaging
        function extraManipulation(pixels) {
            var i = 0, sum = [0, 0, 0, 0];
            while (i < pixels.data.length) {
                sum[0] += pixels.data[i++];
                sum[1] += pixels.data[i++];
                sum[2] += pixels.data[i++];
                sum[3] += pixels.data[i++];
            }

            let divisor = pixels.data.length / 4;

            sum[0] = Math.floor(sum[0] / divisor);
            sum[1] = Math.floor(sum[1] / divisor);
            sum[2] = Math.floor(sum[2] / divisor);
            sum[3] = Math.floor(sum[3] / divisor);

            i = 0
            while (i < pixels.data.length) {
                pixels.data[i++] = sum[0];
                pixels.data[i++] = sum[1];
                pixels.data[i++] = sum[2];
                pixels.data[i++] = sum[3];
            }

            // report back and store average in metadata:
            options.step.metadata.averages = sum;

            // TODO: refactor into a new "display()" method as per https://github.com/publiclab/image-sequencer/issues/242
            if (options.step.inBrowser && options.step.ui) $(options.step.ui).find('.details').append("<p><b>Averages</b> (r, g, b, a): " + sum.join(', ') + "</p>");
            return pixels;
        }

        function output(image, datauri, mimetype) {

            // This output is accessible by Image Sequencer
            step.output = {
                src: datauri,
                format: mimetype
            };
        }

        return require('../_nomodule/PixelManipulation.js')(input, {
            output: output,
            extraManipulation: extraManipulation,
            format: input.format,
            image: options.image,
            callback: callback
        });

    }
    return {
        options: options,
        draw: draw,
        output: output,
        UI: UI
    }
}