As technology advances, many things in our daily lives can be digitized, including our photos. Digitization is an implication that things can be processed by using computers, so photos are not exceptions. In the following paragraphs, the concept of “photo” would focus on the digital images only.
An image processing software called Adobe Photoshop, or simply Photoshop, is very popular for its powerful tools to modify photos. How powerful could it be? Here we will see a few examples.
There is a tool in Photoshop called “Quick Selection Tool”, which can conveniently crop a distinct figure on the photo without including the background. This is basically done by edge detection technique, i.e., Photoshop attempts to check those pixels that have contrasting color comparing with the neighboring pixels.
Another commonly used function is to smooth out rough lines or edges in a photo. This can be done by selecting the desired edges, and then blur it by using any options like Gaussian Blur. Simply speaking, the principle used in Gaussian Blur is that for each selected pixel, we perform averaging of neighboring pixels with the weightings in Gaussian matrix. The weightings are calculated by means of a complicated Gaussian function.
An even more powerful tool in Photoshop is called “Content-Aware Fill”. It can remove any image detail on a photo and automatically fill in the space left behind from the background so it looks as if the removed content never existed. Briefly speaking, the mechanism behind this tool is randomly choosing small regions around the image detail we want to get rid of, and using these small regions to fill in the empty spaces after removal.
One can imagine that using only these three tools in Photoshop to perform a lot of modifications, like adding a new object into a photo followed by smoothing edges, or removing an extra object and use “Content-Aware Fill”. Therefore, no matter we are professionals or laymen, it is not a difficult job for us to change any details in a photo. The problem arises: should we trust a photo anymore? In fact, it depends on how we use this two-edged knife.
If we have taken a photo of nice scenery in a foreign country, and we want to use it as our desktop background, unfortunately there are a few visitors on the photo which obstructed this beautiful scenery, what could we do? In the past, we seem to have no solution except taking the photo by going to that country once again. But with the above tools, we can simply select the visitors, and delete them with the use of “Content-Aware Fill” (see Figure 1). These tools undoubtedly bring us more convenience and in turn save a lot of our time.
Figure 1: before (left) and after (right) the use of “Content-Aware Fill”.
Nevertheless, some people attempt to use these powerful tools to conceal certain facts revealed from the photos. Such act is known as “image tampering”. There can be many reasons behind for doing this, e.g. exaggeration of the facts in news in order to arouse public’s interest (see Figure 2), or even modification of people’s political memories (see Figure 3), etc. Undoubtedly this is not a good phenomenon because if the processing tools are abused, the mass media would not bear its responsibility to deliver the truth.
Figure 2: In this Reuters photo from August 2006 (left), thick black smoke rises above the capital of Lebanon
Figure 3: An original photo of Tiananmen Square (top) and a modified photo of the same scene (bottom). Compared with subjects who saw the real photo of Tiananmen, those who saw the modified photo were twice as likely to estimate that more than 500,000 people had participated.
We come back to the problem of whether we should trust the photos. In my opinion, as long as the modified photos are not doing any harm to any parties, we do not need to bother the originality of the photos. Just like the first imagined situation mentioned above, sometimes the “truths” (obstacles of scenery) are not what we want to see. Getting rid of them may be beneficial to us, since we improve the photos’ quality in the sense of art. However, if the photos are related to some critical issues, such as some historical events or scenes of current news, we should be more sensitive to image tampering.
But how could we know when we should trust a photo? To deal with image tampering, researchers have done a lot in a field called “digital forensic”. Digital forensic is mainly about different techniques that enable us to check whether a photo is modified, such as agreement of lighting environments, detection of chromatic aberration, etc. But one may wonder: how about the laymen? Although we cannot perform those verifications like the researchers, we can still try to make critical judgments on the issues related to the photos, and think about if there could be reasons for someone to modify those photos.
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