Are you aware the role Playboy Magazine has had in the remote sensing and image processing industries? Anyone who has read a selection of image processing books or journals will probably recognise the Lena picture as a standard test image. If you donâ€™t know the image, you can find it here. Lenaâ€™s history is interesting.
It began in 1973 when Alexander Sawchuk, who was then an assistant professor at the USC Signal and Image Processing Institute, was part of a small team searching for a human face to scan for a colleagueâ€™s conference paper. They wanted a glossy image to get a good output dynamic range and during the search someone walked in with the November 1972 issue of Playboy. They used the centrefold image, the Swedish model Lena SĂ¶derberg, so they could wrap it around the drum of their scanner. As they only needed a 512 x 512 image, they scanned the top 5.12 inches of the picture, creating a head shot rather than the original full nude centrefold.
From this beginning Lena, often called Lenna as this was the forename used in Playboy, has gone to be one of the most commonly used standard test images. There are a number of theories of why this is the case, including:
- The image has a good variety of different textual elements, such as light and dark, fuzzy and sharp, detailed and flat.
- The grayscale version contains all the middle grays.
- She has a symmetrical face, making any errors easy to see.
- The image processing community is predominantly male!
Most often the image is used for compression testing, but has also used been used in the analysis of a wide variety of other techniques such as the application of filtering for edge enhancement. Even as recently as three years ago a group of scientists from Singapore shrunk the Lena image down to the width of a human hair as a demonstration of nanotechnology printing.
The wide use of Lena eventually came to the notice of Playboy, after the magazine Optical Engineering put her on their front cover in 1991. The Playboy organisation then tried to assert their copyright, however the genie was out of that bottle given the sheer number of people using it. The following year Optical Engineering reached an agreement with Playboy to continue using the image for scientific research and education. The copyright issues are why we didnâ€™t include the Lena image on the blog, although has been reported that Playboy now overlook the use of the Lena for image processing we decided not to risk it! Playboy did help in the search for Lena in 1997 which enabled her to make a public appearance at the 50th Annual Conference of the Society for Imaging Science in Technology. An article written by Jamie Hutchinson giving a more detailed version of the Lena story can be found here.
Whatâ€™s interesting about Lena is that despite all the technological advancements in the last forty years, she is still used as a standard testing image. Contrast this with the famous Blue Marble image of the Earth taken around the same time by astronauts aboard Apollo 17. The 1972 Blue Marble is probably the most iconic picture of the Earth, and unlike Lena has inspired numerous later images. For example, NASA used the Terra satellite to produce a detailed true-colour image of the Earth in 2002 and then three years later surpassed it with a new image that had twice as much detail as the original. The latest NASA Blue Marble was issued last year, captured by the US DSCOVR Earth observation satellite.
Standard test images are important, but theÂ image processing community should probably start to think about updating the ones we use. Anyone got any ideas?