Add attribute to limit the canvas-height to its container

This patch adds an attribute that, combined with `scale='page-fit'`,
allows to fit the contents inside of the page both with respects to the
width and with respect to the height. Think of it as using
`background-size='contain'` rather than the default behavior of
`background-size='cover'` that `scale='page-fit'` triggers.

Author: lesteenman

dist/angular-pdf.js

@@ -41,6 +41,7 @@
         var pdfDoc = null;
         var pageToDisplay = isFinite(attrs.page) ? parseInt(attrs.page) : 1;
         var pageFit = attrs.scale === 'page-fit';
+        var limitHeight = !!attrs.limitcanvasheight;
         var scale = attrs.scale > 0 ? attrs.scale : 1;
         var canvasid = attrs.canvasid || 'pdf-canvas';
         var canvas = document.getElementById(canvasid);
@@ -73,6 +74,9 @@
               viewport = page.getViewport(1);
               var clientRect = element[0].getBoundingClientRect();
               pageWidthScale = clientRect.width / viewport.width;
+              if (limitHeight) {
+                pageWidthScale = Math.min(pageWidthScale, clientRect.height / viewport.height);
+              }
               scale = pageWidthScale;
             }
             viewport = page.getViewport(scale);

readme.md

@@ -69,6 +69,11 @@ Check [`bower.json` file](https://github.com/sayanee/angularjs-pdf/blob/master/b
       ```html
       <ng-pdf template-url="/partials/viewer.html" scale="page-fit"></ng-pdf>
       ```
+    - `limitcanvasheight` as an option combined with `scale='page-fit'`
+
+      ```html
+      <ng-pdf template-url="/partials/viewer.html" scale="page-fit" limitcanvasheight="1"></ng-pdf>
+      ```
     - `page` as an option for initial page number
 
       ```html