quaggaJS/example/file_input.js

$(function () {
    var App = {
        init: function () {
            App.attachListeners();
        },
        attachListeners: function () {
            var self = this;

            $('.controls input[type=file]').on('change', event => {
                if (event.target.files && event.target.files.length) {
                    App.decode(URL.createObjectURL(event.target.files[0]));
                }
            });

            $('.controls button').on('click', event => {
                var input = document.querySelector('.controls input[type=file]');
                if (input.files && input.files.length) {
                    App.decode(URL.createObjectURL(input.files[0]));
                }
            });

            $('.controls .reader-config-group').on('change', 'input, select', event => {
                event.preventDefault();
                var $target = $(event.target),
                    value = $target.attr('type') === 'checkbox' ? $target.prop('checked') : $target.val(),
                    name = $target.attr('name'),
                    state = self._convertNameToState(name);

                console.log(`Value of ${state} changed to ${value}`);
                self.setState(state, value);
            });
        },
        _accessByPath: function (obj, path, val) {
            var parts = path.split('.'),
                depth = parts.length,
                setter = (typeof val !== 'undefined') ? true : false;

            return parts.reduce((o, key, i) => {
                if (setter && (i + 1) === depth) {
                    o[key] = val;
                }
                return key in o ? o[key] : {};
            }, obj);
        },
        _convertNameToState: function (name) {
            return name.replace('_', '.').split('-').reduce((result, value) => {
                return result + value.charAt(0).toUpperCase() + value.substring(1);
            });
        },
        detachListeners: function () {
            $('.controls input[type=file]').off('change');
            $('.controls .reader-config-group').off('change', 'input, select');
            $('.controls button').off('click');
        },
        decode: function (src) {
            var self = this,
                config = $.extend({}, self.state, { src: src });

            Quagga.decodeSingle(config, result => { });
        },
        setState: function (path, value) {
            var self = this;

            if (typeof self._accessByPath(self.inputMapper, path) === 'function') {
                value = self._accessByPath(self.inputMapper, path)(value);
            }

            self._accessByPath(self.state, path, value);

            console.log(JSON.stringify(self.state));
            App.detachListeners();
            App.init();
        },
        inputMapper: {
            inputStream: {
                size: function (value) {
                    return parseInt(value);
                }
            },
            numOfWorkers: function (value) {
                return parseInt(value);
            },
            decoder: {
                readers: function (value) {
                    if (value === 'ean_extended') {
                        return [{
                            format: 'ean_reader',
                            config: {
                                supplements: [
                                    'ean_5_reader', 'ean_2_reader'
                                ]
                            }
                        }];
                    }
                    return [{
                        format: value + '_reader',
                        config: {}
                    }];
                }
            }
        },
        state: {
            inputStream: {
                size: 800,
                singleChannel: false
            },
            locator: {
                patchSize: 'medium',
                halfSample: true
            },
            decoder: {
                readers: [{
                    format: 'code_128_reader',
                    config: {}
                }]
            },
            locate: true,
            src: null
        }
    };

    App.init();

    function calculateRectFromArea(canvas, area) {
        var canvasWidth = canvas.width,
            canvasHeight = canvas.height,
            top = parseInt(area.top) / 100,
            right = parseInt(area.right) / 100,
            bottom = parseInt(area.bottom) / 100,
            left = parseInt(area.left) / 100;

        top *= canvasHeight;
        right = canvasWidth - canvasWidth * right;
        bottom = canvasHeight - canvasHeight * bottom;
        left *= canvasWidth;

        return {
            x: left,
            y: top,
            width: right - left,
            height: bottom - top
        };
    }

    Quagga.onProcessed(function (result) {
        var drawingCtx = Quagga.canvas.ctx.overlay,
            drawingCanvas = Quagga.canvas.dom.overlay,
            area;

        if (result) {
            if (result.boxes) {
                drawingCtx.clearRect(0, 0, parseInt(drawingCanvas.getAttribute('width')), parseInt(drawingCanvas.getAttribute('height')));
                result.boxes.forEach(box => {
                    if (box !== result.box) {
                        Quagga.ImageDebug.drawPath(box, drawingCtx, 'green', 2);
                    }
                });
            }

            if (result.box) {
                Quagga.ImageDebug.drawPath(result.box, drawingCtx, '#00F', 2);
            }

            if (result.codeResult && result.codeResult.code) {
                Quagga.ImageDebug.drawPath(result.line, drawingCtx, 'red', 3);
            }

            if (App.state.inputStream.area) {
                area = calculateRectFromArea(drawingCanvas, App.state.inputStream.area);
                drawingCtx.strokeStyle = '#0F0';
                drawingCtx.strokeRect(area.x, area.y, area.width, area.height);
            }
        }
    });

    Quagga.onDetected(function (result) {
        var code = result.codeResult.code,
            $node,
            canvas = Quagga.canvas.dom.image;

        $node = $('<li><div class="thumbnail"><div class="imgWrapper"><img /></div><div class="caption"><h4 class="code"></h4></div></div></li>');
        $node.find('img').attr('src', canvas.toDataURL());
        $node.find('h4.code').html(code);
        $('#result_strip ul.thumbnails').prepend($node);
    });
});