Imporvements and lint fix

image-source/image-source-common.ts

@@ -1,4 +1,5 @@
 import http = require("http");
+import types = require("utils/types");
 
 // This is used for definition purposes only, it does not generate JavaScript for it.
 import definition = require("image-source");
@@ -30,8 +31,22 @@ export function fromUrl(url: string): Promise<definition.ImageSource> {
 }
 
 export function fromFileOrResource(path: string): definition.ImageSource {
+    if (!isFileOrResourcePath(path)) {
+        throw new Error("Path \"" + "\" is not a valid file or resource.");
+    }
+
     if (path.indexOf(RESOURCE_PREFIX) === 0) {
         return fromResource(path.substr(RESOURCE_PREFIX.length));
     }
     return fromFile(path);
+}
+
+export function isFileOrResourcePath(path: string): boolean {
+    if (!types.isString(path)) {
+        return false;
+    }
+
+    return path.indexOf("~/") === 0 ||  // relative to AppRoot
+        path.indexOf("/") === 0 ||      // absolute path
+        path.indexOf(RESOURCE_PREFIX) === 0;    // resource
 }

image-source/image-source.d.ts

@@ -4,8 +4,8 @@
 declare module "image-source" {
     
     /**
-    * Encapsulates the common abstraction behind a platform specific object (typically a Bitmap) that is used as a source for images.
-    */
+     * Encapsulates the common abstraction behind a platform specific object (typically a Bitmap) that is used as a source for images.
+     */
     export class ImageSource {
        /**
         * Gets the height of this instance. This is a read-only property.
@@ -104,4 +104,10 @@ declare module "image-source" {
      * @param path The location of the file on the file system.
      */
     export function fromFileOrResource(path: string): ImageSource;
+
+    /**
+     * Returns true if the specified path points to a resource or local file.
+     * @param path The path.
+     */
+    export function isFileOrResourcePath(path: string): boolean
 }