how to add image source link in readme.md code example

Example 1: add image to readme

![alt text](http://url/to/img.png)

Example 2: adding a preview image in readme.md

// method 1


// method 2
![Test Image 3](/3DTest.png)
![Test Image 4](https://github.com/tograh/testrepository/3DTest.png 112)

// last method