Working with the hash value

What is a hash value or why are image patterns more powerful?

A hash value is like a fingerprint - just for a file, not a finger. This means, that the hash value is a unique string, which is calculated from the file content. As a result, a change to a file has a change in the hash value as well.
If just the font color will be changed in a text document, the hash value is completely different - even though the content has remained the same. But that is precisely the point of a hash value: to identify an element 100% .

Applying this to image elements, we can assume, there are almost infinite possibilities to produce a different hash for one single image element.



Comparing hash values:


Hash values

Original image (jpg)


Size of image element and pixelation


Black bar


Horizontal flip


Brightness / Contrastt


Vertical flip / Black-white


With a hash comparison, none of the 5 edited image elements would be recognized/discovered.

DoublePics though found a "match" to the original image element by its pattern processor in each of these image elements - depending on the used search parameters. After all, the content (the image element itself), which counts in the end, is still the same.