Added resizeImage()

webclient/components/utilities/utilities-service.js

@@ -22,7 +22,7 @@
 angular.module('mUtilities', [])
 .service('mUtilities', ['$q', function ($q) {
     /*
-     * Gets the size of an image
+     * Get the size of an image
      * @param {File} imageFile the file containing the image
      * @returns {promise} A promise that will be resolved by an object with 2 members:
      *   width & height
@@ -50,4 +50,89 @@ angular.module('mUtilities', [])
         
         return deferred.promise;
     };
+
+    /*
+     * Resize the image to fit in a square of the side maxSize. 
+     * The aspect ratio is kept. The returned image data uses JPEG compression.
+     * Source: http://hacks.mozilla.org/2011/01/how-to-develop-a-html5-image-uploader/
+     * @param {File} imageFile the file containing the image 
+     * @param {Integer} maxSize the max side size 
+     * @returns {promise} A promise that will be resolved by a Blob object containing
+     *   the resized image data
+     */
+    this.resizeImage = function(imageFile, maxSize) {
+        var self = this;
+        var deferred = $q.defer();
+
+        var canvas = document.createElement("canvas");
+
+        var img = document.createElement("img");
+        var reader = new FileReader();  
+        reader.onload = function(e) {
+
+            img.src = e.target.result;
+
+            var ctx = canvas.getContext("2d");
+            ctx.drawImage(img, 0, 0);
+
+            var MAX_WIDTH = maxSize;
+            var MAX_HEIGHT = maxSize;
+            var width = img.width;
+            var height = img.height;
+
+            if (width > height) {
+                if (width > MAX_WIDTH) {
+                    height *= MAX_WIDTH / width;
+                    width = MAX_WIDTH;
+                }
+            } else {
+                if (height > MAX_HEIGHT) {
+                    width *= MAX_HEIGHT / height;
+                    height = MAX_HEIGHT;
+                }
+            }
+            canvas.width = width;
+            canvas.height = height;
+            var ctx = canvas.getContext("2d");
+            ctx.drawImage(img, 0, 0, width, height);
+
+            var dataUrl = canvas.toDataURL("image/jpeg", 0.7); 
+            deferred.resolve(self.dataURItoBlob(dataUrl));
+        };
+        reader.onerror = function(e) {
+            deferred.reject(e);
+        };
+        reader.readAsDataURL(imageFile);
+
+        return deferred.promise;
+    };
+
+    /*
+     * Convert a dataURI string to a blob 
+     * Source: http://stackoverflow.com/a/17682951
+     * @param {String} dataURI the dataURI can be a base64 encoded string or an URL encoded string.
+     * @returns {Blob} the blob
+     */
+    this.dataURItoBlob = function(dataURI) {
+        // convert base64 to raw binary data held in a string
+        // doesn't handle URLEncoded DataURIs
+        var byteString;
+        if (dataURI.split(',')[0].indexOf('base64') >= 0)
+            byteString = atob(dataURI.split(',')[1]);
+        else
+            byteString = unescape(dataURI.split(',')[1]);
+        // separate out the mime component
+        var mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];
+
+        // write the bytes of the string to an ArrayBuffer
+        var ab = new ArrayBuffer(byteString.length);
+        var ia = new Uint8Array(ab);
+        for (var i = 0; i < byteString.length; i++) {
+            ia[i] = byteString.charCodeAt(i);
+        }
+
+        // write the ArrayBuffer to a blob, and you're done
+        return new Blob([ab],{type: mimeString});
+    };
+
 }]);
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