Resize Images in the Browser

ImageTools.es6

let hasBlobConstructor = typeof(Blob) !== 'undefined' && (function () {
    try {
        return Boolean(new Blob());
    } catch (e) {
        return false;
    }
}());

let hasArrayBufferViewSupport = hasBlobConstructor && typeof(Uint8Array) !== 'undefined' && (function () {
    try {
        return new Blob([new Uint8Array(100)]).size === 100;
    } catch (e) {
        return false;
    }
}());

let hasToBlobSupport = (typeof HTMLCanvasElement !== "undefined" ? HTMLCanvasElement.prototype.toBlob : false);

let hasBlobSupport = (hasToBlobSupport || (typeof Uint8Array !== 'undefined' && typeof ArrayBuffer !== 'undefined' && typeof atob !== 'undefined'));

let hasReaderSupport = (typeof FileReader !== 'undefined' || typeof URL !== 'undefined');

export default class ImageTools {
    static resize(file, maxDimensions, callback) {
        if (typeof maxDimensions === 'function') {
            callback = maxDimensions;
            maxDimensions = {
                width: 640,
                height: 480
            };
        }

        let maxWidth  = maxDimensions.width;
        let maxHeight = maxDimensions.height;

        if (!ImageTools.isSupported() || !file.type.match(/image.*/)) {
            callback(file, false);
            return false;
        }

        if (file.type.match(/image\/gif/)) {
            // Not attempting, could be an animated gif
            callback(file, false);
            // TODO: use https://github.com/antimatter15/whammy to convert gif to webm
            return false;
        }

        let image = document.createElement('img');
            
        image.onload = (imgEvt) => {
            let width  = image.width;
            let height = image.height;
            let isTooLarge = false;

            if (width >= height && width > maxDimensions.width) {
                // width is the largest dimension, and it's too big.
                height *= maxDimensions.width / width;
                width = maxDimensions.width;
                isTooLarge = true;
            } else if (height > maxDimensions.height) {
                // either width wasn't over-size or height is the largest dimension
                // and the height is over-size
                width *= maxDimensions.height / height;
                height = maxDimensions.height;
                isTooLarge = true;
            }

            if (!isTooLarge) {
                // early exit; no need to resize
                callback(file, false);
                return;
            }

            let canvas = document.createElement('canvas');
            canvas.width = width;
            canvas.height = height;

            let ctx = canvas.getContext('2d');
            ctx.drawImage(image, 0, 0, width, height);

            if (hasToBlobSupport) {
                canvas.toBlob((blob) => {
                    callback(blob, true);
                }, file.type);
            } else {
                let blob = ImageTools._toBlob(canvas, file.type);
                callback(blob, true);
            }
        };
        ImageTools._loadImage(image, file);

        return true;
    }

    static _toBlob(canvas, type) {
        let dataURI = canvas.toDataURL(type);
        let dataURIParts = dataURI.split(',');
        let byteString;
        if (dataURIParts[0].indexOf('base64') >= 0) {
            // Convert base64 to raw binary data held in a string:
            byteString = atob(dataURIParts[1]);
        } else {
            // Convert base64/URLEncoded data component to raw binary data:
            byteString = decodeURIComponent(dataURIParts[1]);
        }
        let arrayBuffer = new ArrayBuffer(byteString.length);
        let intArray = new Uint8Array(arrayBuffer);

        for (let i = 0; i < byteString.length; i += 1) {
            intArray[i] = byteString.charCodeAt(i);
        }

        let mimeString = dataURIParts[0].split(':')[1].split(';')[0];
        let blob = null;

        if (hasBlobConstructor) {
            blob = new Blob(
                [hasArrayBufferViewSupport ? intArray : arrayBuffer],
                {type: mimeString}
            );
        } else {
            let bb = new BlobBuilder();
            bb.append(arrayBuffer);
            blob = bb.getBlob(mimeString);
        }

        return blob;
    }

    static _loadImage(image, file, callback) {
        if (typeof(URL) === 'undefined') {
            let reader = new FileReader();
            reader.onload = function(evt) {
                image.src = evt.target.result;
                if (callback) { callback(); }
            }
            reader.readAsDataURL(file);
        } else {
            image.src = URL.createObjectURL(file);
            if (callback) { callback(); }
        }
    };

    static isSupported() {
        return (
               (typeof(HTMLCanvasElement) !== 'undefined') 
            && hasBlobSupport
            && hasReaderSupport
        );
    }
}

ImageTools.js

'use strict';

if (typeof exports === "undefined") {
    var exports = {};
}

if (typeof module === "undefined") {
   var module = {};
}

Object.defineProperty(exports, '__esModule', {
    value: true
});

var _createClass = (function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ('value' in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; })();

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError('Cannot call a class as a function'); } }

var hasBlobConstructor = typeof Blob !== 'undefined' && (function () {
    try {
        return Boolean(new Blob());
    } catch (e) {
        return false;
    }
})();

var hasArrayBufferViewSupport = hasBlobConstructor && typeof Uint8Array !== 'undefined' && (function () {
    try {
        return new Blob([new Uint8Array(100)]).size === 100;
    } catch (e) {
        return false;
    }
})();

var hasToBlobSupport = typeof HTMLCanvasElement !== "undefined" ? HTMLCanvasElement.prototype.toBlob : false;

var hasBlobSupport = hasToBlobSupport || typeof Uint8Array !== 'undefined' && typeof ArrayBuffer !== 'undefined' && typeof atob !== 'undefined';

var hasReaderSupport = typeof FileReader !== 'undefined' || typeof URL !== 'undefined';

var ImageTools = (function () {
    function ImageTools() {
        _classCallCheck(this, ImageTools);
    }

    _createClass(ImageTools, null, [{
        key: 'resize',
        value: function resize(file, maxDimensions, callback) {
            if (typeof maxDimensions === 'function') {
                callback = maxDimensions;
                maxDimensions = {
                    width: 640,
                    height: 480
                };
            }

            var maxWidth = maxDimensions.width;
            var maxHeight = maxDimensions.height;

            if (!ImageTools.isSupported() || !file.type.match(/image.*/)) {
                callback(file, false);
                return false;
            }

            if (file.type.match(/image\/gif/)) {
                // Not attempting, could be an animated gif
                callback(file, false);
                // TODO: use https://github.com/antimatter15/whammy to convert gif to webm
                return false;
            }

            var image = document.createElement('img');

            image.onload = function (imgEvt) {
                var width = image.width;
                var height = image.height;
                var isTooLarge = false;

                if (width > height && width > maxDimensions.width) {
                    // width is the largest dimension, and it's too big.
                    height *= maxDimensions.width / width;
                    width = maxDimensions.width;
                    isTooLarge = true;
                } else if (height > maxDimensions.height) {
                    // either width wasn't over-size or height is the largest dimension
                    // and the height is over-size
                    width *= maxDimensions.height / height;
                    height = maxDimensions.height;
                    isTooLarge = true;
                }

                if (!isTooLarge) {
                    // early exit; no need to resize
                    callback(file, false);
                    return;
                }

                var canvas = document.createElement('canvas');
                canvas.width = width;
                canvas.height = height;

                var ctx = canvas.getContext('2d');
                ctx.drawImage(image, 0, 0, width, height);

                if (hasToBlobSupport) {
                    canvas.toBlob(function (blob) {
                        callback(blob, true);
                    }, file.type);
                } else {
                    var blob = ImageTools._toBlob(canvas, file.type);
                    callback(blob, true);
                }
            };
            ImageTools._loadImage(image, file);

            return true;
        }
    }, {
        key: '_toBlob',
        value: function _toBlob(canvas, type) {
            var dataURI = canvas.toDataURL(type);
            var dataURIParts = dataURI.split(',');
            var byteString = undefined;
            if (dataURIParts[0].indexOf('base64') >= 0) {
                // Convert base64 to raw binary data held in a string:
                byteString = atob(dataURIParts[1]);
            } else {
                // Convert base64/URLEncoded data component to raw binary data:
                byteString = decodeURIComponent(dataURIParts[1]);
            }
            var arrayBuffer = new ArrayBuffer(byteString.length);
            var intArray = new Uint8Array(arrayBuffer);

            for (var i = 0; i < byteString.length; i += 1) {
                intArray[i] = byteString.charCodeAt(i);
            }

            var mimeString = dataURIParts[0].split(':')[1].split(';')[0];
            var blob = null;

            if (hasBlobConstructor) {
                blob = new Blob([hasArrayBufferViewSupport ? intArray : arrayBuffer], { type: mimeString });
            } else {
                var bb = new BlobBuilder();
                bb.append(arrayBuffer);
                blob = bb.getBlob(mimeString);
            }

            return blob;
        }
    }, {
        key: '_loadImage',
        value: function _loadImage(image, file, callback) {
            if (typeof URL === 'undefined') {
                var reader = new FileReader();
                reader.onload = function (evt) {
                    image.src = evt.target.result;
                    if (callback) {
                        callback();
                    }
                };
                reader.readAsDataURL(file);
            } else {
                image.src = URL.createObjectURL(file);
                if (callback) {
                    callback();
                }
            }
        }
    }, {
        key: 'isSupported',
        value: function isSupported() {
            return typeof HTMLCanvasElement !== 'undefined' && hasBlobSupport && hasReaderSupport;
        }
    }]);

    return ImageTools;
})();

exports['default'] = ImageTools;
module.exports = exports['default'];

Thanks! Gracias por la solución!

Here is an updated gist that adds another parameter, avatar, which takes an integer. If supplied, it will scale the image to the avatar parameter, and center-crop the image into a square. Use as ImageTools.resize(event.target.files[0], 90, {...}

'use strict';

if (typeof exports === "undefined") {
    var exports = {};
}

if (typeof module === "undefined") {
   var module = {};
}

Object.defineProperty(exports, '__esModule', {
    value: true
});

var _createClass = (function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ('value' in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; })();

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError('Cannot call a class as a function'); } }

var hasBlobConstructor = typeof Blob !== 'undefined' && (function () {
    try {
        return Boolean(new Blob());
    } catch (e) {
        return false;
    }
})();

var hasArrayBufferViewSupport = hasBlobConstructor && typeof Uint8Array !== 'undefined' && (function () {
    try {
        return new Blob([new Uint8Array(100)]).size === 100;
    } catch (e) {
        return false;
    }
})();

var hasToBlobSupport = typeof HTMLCanvasElement !== "undefined" ? HTMLCanvasElement.prototype.toBlob : false;

var hasBlobSupport = hasToBlobSupport || typeof Uint8Array !== 'undefined' && typeof ArrayBuffer !== 'undefined' && typeof atob !== 'undefined';

var hasReaderSupport = typeof FileReader !== 'undefined' || typeof URL !== 'undefined';

var ImageTools = (function () {
    function ImageTools() {
        _classCallCheck(this, ImageTools);
    }

    _createClass(ImageTools, null, [{
        key: 'resize',
        value: function resize(file, avatar = false, maxDimensions, callback) {
            if (typeof maxDimensions === 'function') {
                callback = maxDimensions;
                maxDimensions = {
                    width: 640,
                    height: 480
                };
            }

            var maxWidth = maxDimensions.width;
            var maxHeight = maxDimensions.height;

            if (!ImageTools.isSupported() || !file.type.match(/image.*/)) {
                callback(file, false);
                return false;
            }

            if (file.type.match(/image\/gif/)) {
                // Not attempting, could be an animated gif
                callback(file, false);
                // TODO: use https://github.com/antimatter15/whammy to convert gif to webm
                return false;
            }

            var image = document.createElement('img');

            image.onload = function (imgEvt) {
                var width = image.width;
                var height = image.height;
                var isTooLarge = false;

				const getWidthHeight = function(img, side) {
				  const { width, height } = img;
				  if (width === height) {
				    return [0, 0, side, side];
				  } else if (width < height) {
				    const rat = height / width;
				    const top = ((side * rat) - side) / 2;
				    return [0, -1 * top, side, side * rat]
				  } else {
				    const rat = width / height;
				    const left = ((side * rat) - side) / 2;
				    return [-1 * left, 0, side * rat, side]
				  }
				}
				
				if (!avatar) {
					if (width > height && width > maxDimensions.width) {
	                    // width is the largest dimension, and it's too big.
	                    height *= maxDimensions.width / width;
	                    width = maxDimensions.width;
	                    isTooLarge = true;
	                } else if (height > maxDimensions.height) {
	                    // either width wasn't over-size or height is the largest dimension
	                    // and the height is over-size
	                    width *= maxDimensions.height / height;
	                    height = maxDimensions.height;
	                    isTooLarge = true;
	                }

	                if (!isTooLarge) {
	                    // early exit; no need to resize
	                    callback(file, false);
	                    return;
	                }
				}

                var canvas = document.createElement('canvas');
                canvas.width = avatar ? avatar : width;
                canvas.height = avatar ? avatar : height;

                var ctx = canvas.getContext('2d');
				ctx.imageSmoothingEnabled = true;
				ctx.imageSmoothingQuality = 'high';
				if (avatar) {
					ctx.drawImage(image, ...getWidthHeight(image, 90));
				} else {
					ctx.drawImage(image, 0, 0, width, height);
				}

                if (hasToBlobSupport) {
                    canvas.toBlob(function (blob) {
                        callback(blob, true);
                    }, file.type);
                } else {
                    var blob = ImageTools._toBlob(canvas, file.type);
                    callback(blob, true);
                }
            };
            ImageTools._loadImage(image, file);

            return true;
        }
    }, {
        key: '_toBlob',
        value: function _toBlob(canvas, type) {
            var dataURI = canvas.toDataURL(type);
            var dataURIParts = dataURI.split(',');
            var byteString = undefined;
            if (dataURIParts[0].indexOf('base64') >= 0) {
                // Convert base64 to raw binary data held in a string:
                byteString = atob(dataURIParts[1]);
            } else {
                // Convert base64/URLEncoded data component to raw binary data:
                byteString = decodeURIComponent(dataURIParts[1]);
            }
            var arrayBuffer = new ArrayBuffer(byteString.length);
            var intArray = new Uint8Array(arrayBuffer);

            for (var i = 0; i < byteString.length; i += 1) {
                intArray[i] = byteString.charCodeAt(i);
            }

            var mimeString = dataURIParts[0].split(':')[1].split(';')[0];
            var blob = null;

            if (hasBlobConstructor) {
                blob = new Blob([hasArrayBufferViewSupport ? intArray : arrayBuffer], { type: mimeString });
            } else {
                var bb = new BlobBuilder();
                bb.append(arrayBuffer);
                blob = bb.getBlob(mimeString);
            }

            return blob;
        }
    }, {
        key: '_loadImage',
        value: function _loadImage(image, file, callback) {
            if (typeof URL === 'undefined') {
                var reader = new FileReader();
                reader.onload = function (evt) {
                    image.src = evt.target.result;
                    if (callback) {
                        callback();
                    }
                };
                reader.readAsDataURL(file);
            } else {
                image.src = URL.createObjectURL(file);
                if (callback) {
                    callback();
                }
            }
        }
    }, {
        key: 'isSupported',
        value: function isSupported() {
            return typeof HTMLCanvasElement !== 'undefined' && hasBlobSupport && hasReaderSupport;
        }
    }]);

    return ImageTools;
})();

exports['default'] = ImageTools;
module.exports = exports['default'];

I'm just using this now: http://nodeca.github.io/pica/demo/