Add contrast module (#463)

src/modules/Contrast/Contrast.js

@@ -0,0 +1,47 @@
+var _ = require('lodash');
+module.exports = exports = function(pixels , contrast){
+	let oldpix = _.cloneDeep(pixels);
+    contrast = Number(contrast)
+	if (contrast < -100) contrast = -100;
+    if (contrast > 100) contrast = 100;
+    contrast = (100.0 + contrast) / 100.0;
+    contrast *= contrast;
+        
+    for (let i = 0; i < oldpix.shape[0]; i++) {
+        for (let j = 0; j < oldpix.shape[1]; j++) {
+        	var r = oldpix.get(i,j,0)/255.0;
+        	r -= 0.5;
+            r *= contrast;
+        	r += 0.5;
+            r *= 255;
+            if (r < 0) r = 0;
+            if (r > 255) r = 255;
+
+
+            var g = oldpix.get(i,j,1)/255.0;
+            g -= 0.5;
+            g *= contrast;
+            g += 0.5;
+            g *= 255;
+            if (g < 0) g = 0;
+            if (g > 255) g = 255;
+        
+
+
+            var b = oldpix.get(i,j,2)/255.0;
+            b -= 0.5;
+            b *= contrast;
+            b += 0.5;
+            b *= 255;
+            if (b < 0) b = 0;
+            if (b > 255) b = 255;
+            
+
+            pixels.set(i, j, 0, r);
+            pixels.set(i, j, 1, g);
+            pixels.set(i, j, 2, b);
+
+        }
+    }
+    return pixels;
+}