Ctor single arg: allow plain object, reject null/undefined

Thank you @kub1x

lib/constructor.js

@@ -5,6 +5,7 @@ const util = require('util');
 const stream = require('stream');
 const events = require('events');
 const semver = require('semver');
+const is = require('./is');
 const sharp = require('../build/Release/sharp.node');
 
 // Versioning
@@ -59,7 +60,7 @@ const debuglog = util.debuglog('sharp');
  *
  * @example
  * // Create a blank 300x200 PNG image of semi-transluent red pixels
- * sharp(null, {
+ * sharp({
  *   create: {
  *     width: 300,
  *     height: 200,
@@ -74,7 +75,7 @@ const debuglog = util.debuglog('sharp');
  * @param {(Buffer|String)} [input] - if present, can be
  *  a Buffer containing JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data, or
  *  a String containing the path to an JPEG, PNG, WebP, GIF, SVG or TIFF image file.
- *  JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data can be streamed into the object when null or undefined.
+ *  JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data can be streamed into the object when not present.
  * @param {Object} [options] - if present, is an Object with optional attributes.
  * @param {Number} [options.density=72] - integral number representing the DPI for vector images.
  * @param {Object} [options.raw] - describes raw pixel input image data. See `raw()` for pixel ordering.
@@ -90,6 +91,9 @@ const debuglog = util.debuglog('sharp');
  * @throws {Error} Invalid parameters
  */
 const Sharp = function (input, options) {
+  if (arguments.length === 1 && !is.defined(input)) {
+    throw new Error('Invalid input');
+  }
   if (!(this instanceof Sharp)) {
     return new Sharp(input, options);
   }

lib/input.js

@@ -16,6 +16,9 @@ function _createInputDescriptor (input, inputOptions, containerOptions) {
   } else if (is.buffer(input)) {
     // Buffer
     inputDescriptor.buffer = input;
+  } else if (is.plainObject(input) && !is.defined(inputOptions)) {
+    // Plain Object descriptor, e.g. create
+    inputOptions = input;
   } else if (!is.defined(input) && is.object(containerOptions) && containerOptions.allowStream) {
     // Stream
     inputDescriptor.buffer = [];

lib/is.js

@@ -16,6 +16,14 @@ const object = function (val) {
   return typeof val === 'object';
 };
 
+/**
+ * Is this value a plain object?
+ * @private
+ */
+const plainObject = function (val) {
+  return object(val) && Object.prototype.toString.call(val) === '[object Object]';
+};
+
 /**
  * Is this value a function?
  * @private
@@ -98,6 +106,7 @@ const invalidParameterError = function (name, expected, actual) {
 module.exports = {
   defined: defined,
   object: object,
+  plainObject: plainObject,
   fn: fn,
   bool: bool,
   buffer: buffer,