Quick Compare the different between Photos, Documents or Drawings.

The app created one base layer and one overlay layer.
Both can be 'Move', 'Scale' and 'Rotate'.
There are three mode can be used in the overlay layer color to assist user to check the relevant Photos, Documents or Drawings.

Mode 1: 50% transparent
- to assist users to check not similar documents.

Mode 2: Invert color
- Invert color to assist users to check similar photos. When the same color overlap, the color will change to gray as the overlay is the invert color of the original photo.

Mode 3: 50% transparent with Red color.
- it mainly for documents or drawings. The different items will easy when observed when there are overlapped. The items not be covered by red color is the different one.

Based on the above design, I hope to help the users to use the App as a tracer light box.
The principle is similar to put 2 papers on the tracer light box to find the different.

It will increase the productivity of the different finding. The original design idea is assisting me to find the different of the drawings and only with Mode 3. From the process, I found that the idea can check photos and document too. Since the above reason , I created both Mode 1 and Mode 2 for different purpose.

The difficult of the App is how to control the scale and rotate and the relationship between base and overlay.

- If you move the base, the overlay will be hide and freeze.
- If you move the overlay, the base can freeze or synchronize with overlay.

I have created a new pinch zoom and rotate gesture for assisting users to accurate pivot point input in the mobile phone. But for the drawings a tablet is more suitable.