Update README.md

Author: YujiSODE

README.md

@@ -9,3 +9,34 @@ ______
 - `dataMappingGuide.js`
 
 ## 2. Synopsis
+`var obj=dataMappingGuide(canvas,src);`  
+This function returns an object with some methods to control.
+
+### Parameters  
+- `canvas`: a canvas element
+- `src`: an optional filename or pathname of an image for background
+
+### Main methods
+#### 1) resizing and background
+- `resize(w,h,src)`; it sets canvas size and background image
+- `setDivisions(x,y)`; it sets horizontal and vertical divisions
+  - `w` and `h`: new values for canvas width and canvas height
+  - `src`: filename or pathname of an image; 'none' is default value
+  - `x` and `y`: numbers for horizontal and vertical divisions
+
+#### 2) colors
+- `setColor(rgb,alpha)`; it sets rgb color and alpha value
+  - `rgb`: rgb color value
+  - `alpha`: an optional value between 0.0 (fully transparent) and 1.0 (fully opaque)
+
+#### 3) focus area
+- `xy(x,y)`; it puts focus on a area that is specified using integer coordinates
+  - `x` and `y`: positive integer indices for horizontal and vertical divisions
+
+#### Focus area indices
+    An example of 3x3 divided focus area:
+    _|1|2|3|
+    1|x|x|x|
+    2|x|x|x|
+    3|x|x|x|
+