IMAGE FORGERY1. DEFINITION AND HISTORY2. TYPES OF IMAGE FORGERY A. IMAGE RETOUCHING B. IMAGE SPLICINGC. COPY AND MOVE ATTACK
Image Forgery is not new. History has recorded that it happens as early as the 1840s. Hippolyta Bayard, the first person to create a fake image as recorded by history, is famous for a picture of him committing suicide (see picture on the left). It all started as an act of frustration because he had lost the chance of becoming the inventor of photography to Louis Daguerre. Daguerre patented a photography process earlier than him and owns all the glory . Digital Image Forgery does not differ very much in nature compared to conventional Image Forgery. Instead of using photograph, digital image forgery deals with digital image. The process of creating fake image has been tremendously simple with the introduction of powerful computer graphics editing software such as Adobe Photoshop, GIMP, and Corel Paint Shop, some of which are available for free. There are many cases of digital image forgery. All of these cases can be categorized into three major groups, based on the process involved in creating the fake image. The groups are Image Retouching, Image Splicing, and Copy-Move Attack.
Image Retouching can be considered to be the less harmful kind of digital image forgery. Image retouching does not significantly change an image, but instead, enhances or reduces certain feature of an image (see picture below). This technique is popular among magazine photo editors. It can be said that almost all magazine cover would employ this technique to enhance certain features of an image so that it is more attractive; ignoring the fact that such enhancement is ethically wrong.
This technique is more aggressive than image retouching. Image Splicing is a technique that involves a composite of two or more images which are combined to create a fake image. In the picture below, the shark is copied to the base image (helicopter rescue). The base image is first flipped horizontally before the shark is pasted to create a more convincing (and not to forget dramatic) picture of a helicopter rescue.
Copy-move attack is more or less similar to Image Splicing in view of the fact that both techniques modify certain image region (of a base image), with another image. However, instead of having an external image as the source, copy-move attack uses portion of the original base image as its source. In other words, the source and the destination of the modified image originated from the same image. In a copy-move attack, parts of the original image is copied, moved to a desired location, and pasted. This is usually done in order to conceal certain details or to duplicate certain aspects of an image. Blurring is usually applied along the border of the modified region to reduce the effect of irregularities between the original and pasted region . The picture below shows a sample image that has been tampered using copy-move attack (left) and its original (right). Notice a repeated smoke pattern on the left image.
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The Internet is a great way to show your photographs to the world.Putting images up on a web site is child’s play compared to hanging a gallery show or publishing a book. But what is to stop anunscrupulous web site visitor from stealing your images? In truth, all the images that are seen by your visitors are already copied and stored in their computer’s browser cache. But there are still effective, low cost ways of preventing their misuse.
Adding Your Copyright as aText LayerThis is the easiest and most effective way to protect yourimages. Placing the copyright symbol and your name directly inan image tells everyone that your work is copyrighted. Werecommend including your web site URL (or phone number ifyou don’t have your own web site) so anyone who prints out orcopies your picture can easily find you in the future. This turnsevery copied image into an advertisement for you.Each graphics program handles text differently, but look forthe Text Tool on the tool bar within your program. Use an easyto read font like Arial in a small point size. If your image haslight and dark areas that make text hard to read you can selectthe area behind the text and reduce its contrast.
Size and Compress YourImages ProperlyThere are two benefits to this approach. Smaller images willreduce both the quality of a printout and will also speed pageload time. Keep your image size to under 450 pixels on the longdimension. If anyone were to print it, it would either print small,or if forced to be a larger print the image will look pixilated(pixels will spread out). Next, compress your images until theyjust begin to show artifacts. This will help them load faster, andfurther reduce the chance they will be misused. We recommendusing one of the side by side compression tools that give you avisual confirmation of how much you can compress the imagebefore it starts to visually degrade. Photoshops "Save For Web"(also available in Photoshop Elements) is our tool of choice.
Image Slicing to protectyour imagesUsing your graphics program, you can slice your pictures intotwo or more slices. Right clicking and saving would only getthe view the part of the picture that was clicked on. And thebrowsers cache will only have fragmented bits of images in it.The individual image parts, which are really separate,pictures loading into different cells within the same table, arejoined in the HTML when viewing the image on the web. Anadded benefit of slicing is shorter load time when youoptimize each slice individually. In a program likeImageReady (part of Photoshop 6), different parts of thesame image can be optimized as Gif’s or Jpeg’s