Merge pull request #30 from randytarampi/feat/pull-dominantColors

Pull `dominantColor`s per #28

Closes #28 and EyalAr#255

README.md

@@ -59,6 +59,7 @@ This is a branch based off of [@kant2002/lwip](https://www.npmjs.com/package/@ka
       0. [GIF](#gif)
     0. [Write to file](#write-to-file)
     0. [Get metadata](#get-metadata)
+    0. [Get dominant color](#get-dominant-color)
   0. [Batch operations](#batch-operations)
 0. [Copyrights](#copyrights)
 
@@ -739,6 +740,14 @@ tEXt chunks in PNG images, and will get the first tEXt chunk found with the key
 
 `image.getMetadata()`
 
+### Get dominant color
+
+Get the pixel color that occurs most frequently in a picture.
+
+`image.dominantColor(pixels_to_skip)`
+
+0. `pixels_to_skip {Int}`: the number of pixels to skip while iterating through the image. Ex. supplying 1 will skip every other pixel, 0 will skip none. The greater the number the less accuracy the result will have.
+
 ### Batch operations
 
 Each of the [image operations](#image-operations) above can be done as part of

lib/Image.js

@@ -34,7 +34,8 @@ const judges = {
     toBuffer: decree(defs.args.toBuffer),
     writeFile: decree(defs.args.writeFile),
     setPixel: decree(defs.args.setPixel),
-    getPixel: decree(defs.args.getPixel)
+    getPixel: decree(defs.args.getPixel),
+    dominantColor: decree(defs.args.dominantColor)
 };
 
 module.exports = class Image {
@@ -82,6 +83,47 @@ module.exports = class Image {
         };
     }
 
+    dominantColor () {
+        let dominantColor;
+        judges.dominantColor(
+            arguments,
+            skips => {
+                if (typeof skips !== 'number' || skips < 0 || parseInt(skips,10) !== skips) {
+                    throw Error('Pass a positive integer argument for number of pixels to skip over each iteration');
+                }
+
+                const colorCounter = {};
+                for (let i = 0; i < this.width(); i++) {
+                    for (let j = 0; j < this.height(); j+= skips+1) {
+                        const pixel = this.__lwip.getPixel(i,j),
+                            pixelColor = pixel[0].toString()+','+pixel[1].toString()+','+pixel[2].toString()+','+pixel[3].toString(),
+                            occurence = colorCounter[pixelColor];
+                        if (occurence === undefined) colorCounter[pixelColor] = 1;
+                        else colorCounter[pixelColor]++;
+                    }
+                }
+
+                let the_key = '0,0,0,0',
+                    count = 0;
+                for (let key in colorCounter) {
+                    if (colorCounter[key] > count) {
+                        the_key = key;
+                        count = colorCounter[key];
+                    }
+                }
+                the_key = the_key.split(',');
+
+                dominantColor = {
+                    r: parseInt(the_key[0],10),
+                    g: parseInt(the_key[1],10),
+                    b: parseInt(the_key[2],10),
+                    a: parseInt(the_key[3],10)
+                };
+            }
+        );
+        return dominantColor;
+    }
+
     getPixel () {
         const args = judges.getPixel(arguments),
             left = args[0],