The Hindu Business Line : Change your image

This essentially enables horizontal or vertical scaling of images according to context and medium with least visual disruption, besides addition of pixels when image dimensions have to be increased, they say.

Speaking to eWorld in an e-mail interaction, Dr Avidan, whose research is about understanding, analysing and editing images, says the goal of the technology is to allow images to adapt to their display, “so that an image to be displayed on your cell-phone should be different from an image shown on a 50-inch plasma TV.” A five-minute video demonstrating this technology was voted top serious video on YouTube recently.

Observers hail the technology as a new paradigm in digital effects, as it helps in cutting out unwanted portions of a picture, apart from adding pixels to enlarge an image, a process the inventors refer to as ‘retargeting.’ Explaining the process, Dr Avidan says effective resizing of images should not only use geometric constraints but consider the image content as well. “We present a simple image operator called seam carving, which supports content-aware image resizing for both reduction and expansion. It can change the size of an image by gracefully carving out or inserting pixels in different parts of the image.”

Seam carving uses an energy function defining the importance of pixels. A seam is a connected path of low-energy pixels crossing the image from top to bottom, or from left to right. By successively removing or inserting seams, one can reduce, as well as enlarge, the size of an image in both directions.

For image reduction, seam selection ensures that while preserving the image structure, more of the low-energy pixels and fewer of the high-energy ones are removed.

For image enlargement, the order of seam insertion ensures a balance between the original image content and the artificially inserted pixels. These operators produce, in effect, a content-aware resizing of images.

On the rationale behind developing such a technology and what gaps it seeks to fill, Dr Avidan says the diversity and versatility of display devices today imposes new demands on digital media. “For instance, designers must create different alternatives for Web content and design different layouts for different devices. Moreover, HTML, as well as other standards, can support dynamic changes of page layout and text. Nevertheless, up-to-date images, despite being one of the key elements in digital media, typically remain rigid in size and cannot deform to fit different layouts automatically.”

Other cases in which the size or aspect ratio of an image must change are to fit into different displays such as cellular phones, PDAs or to print on a given paper size or resolution. Dr Avidan asserts that standard image scaling is not sufficient since it is “oblivious to the image content and can typically be applied only uniformly. Cropping is limited since it can only remove pixels from the image periphery. More effective resizing can only be achieved by considering the image content and not only geometric constraints.” Using this technique, a designer can author a multi-size image once, and the client application, depending on the size needed, can resize the image in real time to fit the exact layout or the display.

The two scientists developed the technology while with Mitsubishi Electric Research Labs (MERL), which has filed for a patent. Dr Shamir is now with the Interdisciplinary Centre (IDC) at Israel, while Dr Avidan recently joined Adobe Systems.

Is there a possibility of the technology changing the way one views images on the Net? Dr Avidan says, “Hopefully this technology can be incorporated into the browser as follows: The Web designer can determine, ahead of time, how an image should be retargeted. As the client changes the size of his browser window, the images on this Web page will change according to decisions made, ahead of time, by the Web designer.”

cram@thehindu.co.in

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