How to compare PNG pictures by C#

// Construct report about changes in PNG images

// Create Comparer pointing to the first file
using (Comparer comparer = new Comparer("source.png"))
{
    // Involve other pictures to comparison process
	comparer.Add("file_to_compare_1.png");
    comparer.Add("file_to_compare_2.png");
    comparer.Add("file_to_compare_3.png");

    // Enjoy the resulting report
    comparer.Compare("result.png"); 
}