If an image has been manipulated, edited or just cropped in a clever way, reverse image search might not provide any useful results. If so, the next step could be to look for traces of the manipulation.
This isn’t easy, and it demands that you’ve found an anomaly – something that’s made you suspicious – with your bare eyes. But if that’s the situation, there are tools that could help you find exactly what’s been altered in an image.
The most commonly used one is Forensically. (Live demonstration)
When we first open the site, we can see a very clear example of an altered photography. We might immediately suspect that the UFO has been added to the image. But how could we confirm that? Well, let's look at the menu to the right.
Here are tools for all sorts of investigations. To learn more about each one, you could click the “Help” tab in the upper left. But for now, we’ll focus on two of them. The first one is Noise analysis. It’s a tool that detects whether elements have been added to an image.
Every image consists of a certain amount of pixels – more pixels in the same area means a higher resolution. This is usually referred to as “pixel density”. But if you add elements from one picture to another, it’s likely that there will be differences in pixel density. That’s what Noise analysis helps you detect.
So in this example, we can clearly see that the UFO has been added to the image – the UFO came from a picture with another pixel density, which is most often the case when you merge images.
But I want to add a warning: if you merge two pictures and then take a screenshot of the result, the screenshot will have a perfectly uniform pixel density. So the differences that were there in the original image, will have been removed.
Therefore it’s completely possible that an image has been altered even though Forensically can’t find the traces of it – this is important to be aware of, it’s just one tool in the toolbox.
The next tool we’ll use in this example is clone detection. Because if you want to remove something from an image, you need to add something else to fill the void. Most often you “clone” a similar area in the same picture, to make sure the lightning, colours and contrasts stay the same. While such cloning might be difficult to discover without a tool, Forensically makes it easy.
If we use clone detection on this image, we’ll see clearly that the clouds have been duplicated. Perhaps something was removed from the sky, and replaced with these – perhaps a real UFO?
So it’s time you get to try Forensically for yourselves. Let's get down to the exercises.