Added Edge Detection module (#168)

* step 1 grayscale

Signed-off-by: tech4GT <varun.gupta1798@gmail.com>

* add basic edge detection resolves #166

* updated the description

Signed-off-by: tech4GT <varun.gupta1798@gmail.com>

* fixed typo

Signed-off-by: tech4GT <varun.gupta1798@gmail.com>

* updated the description for edge detection module

Signed-off-by: tech4GT <varun.gupta1798@gmail.com>

* add NonMaxSuppression and DoubleThreshold

Signed-off-by: tech4GT <varun.gupta1798@gmail.com>

* comlpeted edge detection

Signed-off-by: tech4GT <varun.gupta1798@gmail.com>

* cleared remaining weak edges

Signed-off-by: tech4GT <varun.gupta1798@gmail.com>

src/modules/EdgeDetect/Module.js

@@ -0,0 +1,65 @@
+/*
+ * Detect Edges in an Image
+ */
+module.exports = function edgeDetect(options,UI) {
+
+    options = options || {};
+    options.title = "Detect Edges";
+    options.description = "Detects the edges in an image";
+    options.blur = options.blur || 2
+    options.highThresholdRatio = options.highThresholdRatio||0.2
+    options.lowThresholdRatio = options.lowThresholdRatio||0.15
+  
+    // Tell UI that a step has been set up.
+    UI.onSetup(options.step);
+    var output;
+  
+    // The function which is called on every draw.
+    function draw(input,callback) {
+  
+      // Tell UI that a step is being drawn.
+      UI.onDraw(options.step);
+  
+      var step = this;
+
+
+    //   Extra Manipulation function used as an enveloper for applying gaussian blur and Convolution
+      function extraManipulation(pixels){
+        pixels = require('ndarray-gaussian-filter')(pixels,options.blur)
+        return require('./EdgeUtils')(pixels,options.highThresholdRatio,options.lowThresholdRatio)
+      }
+  
+      function changePixel(r, g, b, a) {
+        return [(r+g+b)/3, (r+g+b)/3, (r+g+b)/3, a];
+      }
+  
+      function output(image,datauri,mimetype){
+  
+        // This output is accessible by Image Sequencer
+        step.output = {src:datauri,format:mimetype};
+  
+        // This output is accessible by UI
+        options.step.output = datauri;
+  
+        // Tell UI that step has been drawn.
+        UI.onComplete(options.step);
+      }
+  
+      return require('../_nomodule/PixelManipulation.js')(input, {
+        output: output,
+        changePixel: changePixel,
+        extraManipulation: extraManipulation,
+        format: input.format,
+        image: options.image,
+        callback: callback
+      });
+  
+    }
+  
+    return {
+      options: options,
+      draw:  draw,
+      output: output,
+      UI: UI
+    }
+  }