GroupDocs.Comparison is a document comparison API that correlates content and style, it detects number of inserted/deleted or style changed items and generates a summary.
How GroupDocs.Comparison works for Image Comparison?
The comparison starts with the upper left corner and compares the entire image pixel by pixel. If the pixels are the same, it moves on to the next one and so on until it finds a difference. The changed pixels are given an ID. It is defined as dabbed, deleted or changed. They are highlighted in a specific color (blue, red or green according to the standard settings).
Target Image is same as source image except it has some extra objects on the table and some new code lines in the text editor.
API successfully detects the changes and highlights them in the output/resultant image. In this case it highlighted the inserted items (e.g glasses, mug and some changes in the code).
This is how you do image comparison using GroupDocs.Comparison for .NET
And using GroupDocs.Comparison for Java