Add support for bit depth with raw input and output (#2762)

* Determine input raw pixel depth from the given typed array
* Allow pixel depth to be set on raw output

lib/is.js

@@ -49,12 +49,26 @@ const buffer = function (val) {
 };
 
 /**
- * Is this value a Uint8Array or Uint8ClampedArray object?
+ * Is this value a typed array object?. E.g. Uint8Array or Uint8ClampedArray?
  * @private
  */
-const uint8Array = function (val) {
-  // allow both since Uint8ClampedArray simply clamps the values between 0-255
-  return val instanceof Uint8Array || val instanceof Uint8ClampedArray;
+const typedArray = function (val) {
+  if (defined(val)) {
+    switch (val.constructor) {
+      case Uint8Array:
+      case Uint8ClampedArray:
+      case Int8Array:
+      case Uint16Array:
+      case Int16Array:
+      case Uint32Array:
+      case Int32Array:
+      case Float32Array:
+      case Float64Array:
+        return true;
+    }
+  }
+
+  return false;
 };
 
 /**
@@ -119,7 +133,7 @@ module.exports = {
   fn: fn,
   bool: bool,
   buffer: buffer,
-  uint8Array: uint8Array,
+  typedArray: typedArray,
   string: string,
   number: number,
   integer: integer,