How to discover if an image has been retouched
Photoshop just turned twenty. Since its appearance has changed irreversibly the way we see the images. Before blindly trusted in the pictures provided means, now, doubt has become systematic.
How can trust what we see and defend against misleading photos ? Train your eye by visiting sites like Worth1000 help, but learning is a slow and difficult to explain. Access to the image in digital format, however, opens the door to search techniques and analysis.
In this article we present programs and techniques to see if what you see is real or a hoax. No system is foolproof, and that any photo can escape, but it's hard to resist a false image of the combined attack of these methods.
1. Find similar images
The first step is almost common sense: you have to know where it comes from the image . A famous photo double in a matter of hours hundreds of forums, blogs and news portals. In these cases, knowing from where the original is difficult, but there are tools to discover.
TinEye An example of the similarities TinEye is able to establish from an image.
One of the most powerful is TinEye , an image search engine. Just enter the URL of the photo or upload a copy of it in JPG format to TinEye search for similar images in seconds. The size is a valuable sort: maintaining the same quality, a copy can not be larger than the original.
Gazopa en accion GazoPa is a valid alternative to TinEye
There are more image search based on their content ( CBIR ) and Bing Pictures or GazoPa . The latter seeks even in the frames of videos posted on the web, news portals, Twitter messages and, more importantly, in the vast collection of Flickr . A visit to the Museum of Hoaxes not hurt.
Panoramio y Barcelona Only the most important places can boast of such density photo
Would you like to find the place where the photo was taken? Sites like Panoramio , Google Street View or Flickr are very helpful when checking the appearance of many places. Of course, need to have data or a previous hypothesis about what could be the scene.
2. To see the metadata
Most image files contain metadata , which are not simply the text that digital cameras and editing programs recorded in photographs. To access this information need an EXIF reader .
Exif Toolbox Exif Toolbox integrates with the Explorer context menu
The information you can get is great , camera model, exposure and sensitivity settings, time of day the photo was taken, GPS coordinates (if the device has geo-tagging unit), and so on. Even more important are some fields that let you know which program is stored or manipulated photo.
Las etiquetas delatoras Unless the user to hide, Flickr shows EXIF
The fields you see in the capture, as software or modification date, show that the original image is not the camera, but a copy kept in an image editor. This does not necessarily mean that the photo has been retouched, perhaps the author only wanted to convert from one format to another or trimming.
Metastripper Programs like MetaStripper remove all EXIF and IPTC metadata
The major drawback is that the EXIF metadata are manipulated. In the worst case, half attacker could edit the metadata to provide a credible profile photo.
3. Analysis con JPEGSnoop
The scientific police from around the world have special tools for the analysis of any type of document, including photographs. Obviously, this type of software is not only costly, but its use is restricted. Fortunately, there are free programs that analyze the background picture to extract a verdict . The most famous is JPEGSnoop .
JPEGSnoop con una foto auténtica The photo has all the earmarks of being genuine, Watson …
JPEGSnoop not only reads the file metadata, but also extracts data on levels of compression, a kind of "fingerprint" that can recognize the program under which the photograph was published. Once you drag and drop the file into the window JPEGSnoop, it will process it immediately.
¡Esta ha sido manipulada!
You'll get a long text report, what is most important, the verdict about the authenticity of the image, is the end. To simplify interpretation of results, images JPEGSnoop divided into four classes:
* Class 1 – The image has been processed / edited
* Class 2 – High probability of processing / editing
* Class 3 – High probability of being the original image
* Class 4 – It is unclear whether it has been processed or original
Caution: this information only indicates whether there is fresh from the original camera or a saved version afterwards. In spite of ourselves on the trail of a possible manipulation, the result JPEGSnoop is not sufficient evidence to confirm whether an image has been retouched or not. Missing more subjective criterion, that of visual inspection.
4. The clinical eye
Why so many programs if the alterations are recognized at first sight? Because often we fail to discover false images, especially if we do not know what to look for, we know the techniques of retouching or we trust in excess of our sources of information.
Qinghai-Tiber Railway Weiqing Liu said he had taken eight hours to take this picture, in fact, merged two different images.
The research group of Hany Farid of Dartmouth College, has assembled an impressive collection of retouched images (the originals are on the right). Serve very well to present four simple pattern recognition:
* Inconsistencies in the lighting: a bright area is not always plausible.
Condoleeza Rice
* Repeating patterns (cloned): lack of variety is a clear sign of manipulation.
Columna de humo
* Anatomical abnormalities: failure proportions or the skin tone look away.
El anuncio de Microsoft Polonia
* Excessive softness or cleaning of an area: the reality has textures!
Sarkozy
Although there are more indicators of handling, these are the most obvious. The lack of more photographs of the same event or concealment of EXIF data increases the suspicions against an incredible photo.
Stellarium Stellarium calculates the sky brightness of a place, date and time specific
Check the events depicted is also useful: after hour, day and site you can find the direction of sunlight, near the official events, local flora and fauna, weather and much more.
Do you know any other program, website or trick to recognize past images by Photoshop? When does a photo you cry "is false"?
Via: How to discover if an image has been retouched
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