Should I be 100% truthful while writing my Personal Statement for Graduate application? Let us think about this question in my online application.

Personal Statement:
Please describe your specific area of academic interest, and explain what motivated you to choose this area.

In my case 100% true answer would be the following,

I am interested in Image Processing.
When I was searching for a supervisor, I met one of the most prominent research professors of the XYZ University Prof. xyz who works in the area of Image Processing, Computer Vision, Graphics and so on. I was interested in Computer Graphics and proposed his a topic. He told me that topic was not fit for MSc thesis to be completed in 4 months. That would actually take more time may be up to a year. Since, I didn't have any other topic in my mind, I requested him to propose a topic for me. He then proposed a topic related to Image Processing. I found that topic very interesting and saw a huge opportunity to learn about the area of Image Processing from the inside.

Is that a good answer?
Yes, the Bob version of your paragraph is a good start.  But if you want to make an impact on the admissions committee, you're going to have to find out a lot more about your topic, so that you can speak about it in more detail.