Infra-Red/UV Video Image
Segmentation Technique Theory
Mickael Maddison, May 2010
Currently the movie and photography industries utilize techniques often referred to as “chroma-key”, “luma-key” or “thermo-key” to film subjects for the purpose of removing the subject from the background of the image. Once the subject is removed from the background of the image, the subject can then be superimposed on alternative backgrounds. For example, filming an actor in front of a “green screen” and using the chroma-key technique to remove the actor from the green background would allow the video editor to place the actor on an image of the moon; without ever having to go to the moon.
Existing techniques for image segmentation require very careful and often expensive settings, lighting and filming techniques in addition to powerful post-production processing to achieve a quality result. This document proposes the use of the Near-infrared spectrum and optional ambient UV to replace the background; allowing for a much simpler means of extracting the desired image from an infrared background. Using a selection of isolated IR wavelengths and CCD or CMOS digital camera technologies adapted to capture and record these isolated wavelengths while at the same time recording the standard RGB (Red Green Blue) or RGBY (Red Green Blue Yellow) visible light would allow for software and devices to be produced will allow subject(s) to be removed from backgrounds with a higher degree of accuracy while requiring far less effort and processing.
* Adding in the detection of UV spectrum will also allow for additional processing options.
Uses: Cameras equipped with combined RGB/RGBY and IR/UV CMOS or CCD sensors would have a wide variety of uses.
- Standard Video capture and recording.
- Image Segmentation.
- Capturing and recording Near-infrared and UV used for special effects/artistic purposes.
- Capturing a wide range of light spectrum useful for night-vision image capture.
- Reconnaissance and security systems.
- Scientific research requiring combined access to visible and non-visible spectrum images.
- Other techniques and uses not yet considered or developed.
1 – CCD: Existing CCD and CMOS sensors already have the capability to record near-infrared wavelengths. Most cameras use a special filter to block the infrared wavelengths from being captured. Cameras that do not have this filter in place store the infrared information in the RGB image. Currently, CCD and CMOS type sensors capture RGB light by using a special “Bayer Color Filter” as seen here:
Each square represents one “pixel” of information captured by the sensor. Processing techniques may vary, but in effect a square of 4 pixels are combined to create a single pixel of “true” color.
The following is an example of how a new filter could be designed to allow for the capture of the additional non-visible spectrum using the existing sensors:
In this sample image, instead of using a pattern of 4 pixels, the pattern is spread over 9 pixels. The 4 existing RGB pixels are captured in addition to 5 additional pixels as represented by the white and various shades of grey boxes. The optimal configuration is subject to analysis, but for example it could be laid out like this:
Red = Red, Blue = Blue, Green1/2 = Green1/2
White = wide-spectrum UV
lightest grey = 840nm IR, second-lightest grey = 900nm IR
third-lightest grey = 950nm, darkest grey = 1000nm OR wide-spectrum IR.
As a future consideration, there are also technologies coming that could utilize the optical properties of carbon nanotubes to capture information on specific wavelengths. Research has shown that a single carbon nanotube connected to a pair of electrodes can can measure IR radiation effectively. This technology may be a long way from practical use, however, it provides an ongoing opportunity to continue developing and refining the technology.
2 – File Format: In addition to the filter, a new image/video file format would be created to store the captured information in a useful format. Many cameras have built-in processors that convert the RAW pixel data from the CCD into consumer file formats such as mpeg, jpeg, tiff, etc. A new processor may be developed to provide traditional file formats + a masking file, or for more advanced use the camera may save all the data together to allow for more advanced processing and usage of the recorded data.
The new image/video RAW format would have more information available and would need to store unique information for each displayed pixel to be effective for image external processing.
3 - Software: Image and video editing software would require modifications and/or filters to be developed that would make full use of the extended information available through the new file format and/or the processing of the masking file with the video file. This may be modifications and additions to versions of existing industry-standard software. In addition, research may deem entirely new software should be developed to make full and wider ranging use of the data.
Some image processing systems have experimented using non-visible light to increase the accuracy and quality of the visibly produced image. For the purpose of image segmentation, the various wavelengths of non-visible light would be used to create highly detailed “mask(s)” useful for cropping the background from the desired image(s).
4 - Non-Visible Illumination: To make the most of the technology, a wide range of electronic devices would be developed as the technology is adopted by the relevant industries. Some examples of devices that would be developed and produced:
- IR floodlights – wavelength specific floodlights to provide a suitable non-visible background.
- IR spotlights – wavelength specific spotlights that could be used to segment multiple objects within a single image by using multiple wavelengths.
- IR backdrops – currently most greenscreen type applications use light shining evenly onto a controlled, smooth surface. An IR backdrop could be a “screen” that actually emits the light from it’s surface.
- IR/RGB backdrops – Using modifications of technologies that are hitting the market today, large LCD screens using LED backlight technology could be redeveloped to emit a combination of visible and non-visible light, allowing a for a fully visible background while at the same time providing the non-visible background needed for image segmentation.
- IR absorbing and reflecting materials – these could be used to achieve a variety of effects. For example, the current industry uses chroma-suits to allow the segmentation of parts of a subject such as a body-less person.
Benefits of the Technology
- Subjects could be photographed or filmed against a variety of backgrounds and still be easily removed from the scene.
- Subjects could be filmed with against a background that has similar colors and textures to the scene they would be placed into. For example, an actor could be filmed against a projection of a mountain scene similar to the one that will be added during post production. This would allow for complex images such as hair to more easily be segmented with minimal artifacts.
- A single background could be used for full color filming, even if the background color matches the color of subjects being segmented from the scene.
- Shadows appearing on the background may have little or no effect on the IR mask, allowing lighting of the subject to be tailored to the final scene rather than to achieving the best separation of color from the green screen.
- Artistic photography, such as family portraits, would be able to eliminate the need to have a wide variety of backgrounds available to photograph subjects against. Instead, the photographer would use a generic or projected image as the background. After (or during) the photography session, the photographer could select the actual background image from an unlimited selection of background images. This allows the photographer to use a single quality photograph for any number of scenes.
Patent and related technology research:
Live Action Compositing example http://www.scribd.com/doc/654481/Live-Action-Compositing
Using human-IR heat for image segmentation http://nae-lab.org/project/thermo-key/
This is not for IR - it is a device that uses a mapped background
Practical Example of Theory
Sony DCR DVD203 Digital Camcorder used in photograph mode.
IR narrow-beam floodlight (wide beam would be much more effective)
Blue floor mat for background
Doll with hair
A Dark room
Computer system with Adobe Photoshop Elements 8.0
Step 1 - photograph still image of subject in Nightshot plus mode which uses NIR to enhance image visibility.
Step 2 - photograph still image of subject in normal RGB mode (sorry for poor quality photo).
Step 3 - Open these to images into a single layered file in Photoshop (elements)
Step 4 - On the nightshot (Mask) layer, convert to B/W and increase contrast and in this case, with a blue background used, I adjust the blue level to get the best differential I can considering the poor lighting. You can see in this step that the segmentation opportunity is pretty good but not nearly perfect. The beam from the IR spotlight is a little too intense and focused. Developing proper Infra-Red lighting would not be difficult, at least in this scene.
Step 5 - Due to inadequate lighting I will cut excess dark regions (which would normally appear as a fairly even white background with proper IR lighting) and delete to pure white to match the area around the subject. As part of this step I have increased the contrast to show clearly the mask that was created. Proper lighting and some minor filtering would remove the manual portions of this step making it easy to automate.
Step 6 - Using magic wand (which would be an automated part of the process) I select all the white area and invert the selection to have the mask selected.
Step 7 - switch to the layer with the RGB image and copy the subject and paste into a new layer.
Step 8 - Turn off the visibility on all layers except the cutout of the subject. You now have a fairly good cutout of the subject to work with.
Step 9 - Insert background and adjust cutout layer as desired.
Due to nightshot plus mode captures IR data and incorporates this into an RGB image. Due to this, the Mask layer is not nearly as good quality as if an actual IR layer were saved in addition to the RGB layer. This limitation also requires the Mask layer of the subject to be shot in (visible) darkness to generate a strong contrast. The RGB layer is then shot in RGB mode with visible lights enabled. If I had 2 nightshot cameras of the same type, split the image into the 2 cameras, and had a filter on the RGB mode camera to remove all IR data and a filter on the nightshot mode camera to remove all RGB data I believe I would get a much more accurate mask.
For example, in unedited images you can see that the hair sticking up off the head is visible. With even IR lighting and no conflicting RGB data being stored on the mask layer, this should result in an even sharper, more accurate mask layer. The sharper, more accurate mask layer could then be used to cut out these fine details from the RGB subject layer, providing a nice crisp image to work with.
Also of note based on previous experience doing still-frame image compositing the process outlined in this document was very quick and simple to do. With proper camera(s), proper lighting, suitable software, and a good studio environment the results should be far better than this simple test.
Well, it has been at least a couple of years since I've found myself drinking “Wonder Tea” at The Grind; yet here I am sitting and enjoying the familiar atmosphere of the same coffee house where I met my loving wife. As I sip my tea and await the arrival of Suzi Rawn, I find it interesting that I am actually somewhat nervous. Perhaps it's the realization of just how huge the whole Canadian Idol phenomenon is, and the fact that I am interviewing a rising star that causes my stomach to flutter? Fortunately, the wait is short. Suzi has arrived.
After a quick introduction and an exchange of CD's, I start off by trying to find out “who is Suzi Rawn?”. Born in Sault Ste Marie Ontario, Suzi became interested in performance arts at a young age. She took some singing lessons and started writing songs when she was 11. Suzi also spent time performing in choirs and taking dance lessons including ballet, hip-hop, jazz and swing. A well traveled Canadian, eventually she lands in the beautiful Shuswap and graduates from high school in the lakeside town of Salmon Arm.
In the 5 short years since, Suzi has had quite an adventure. Heading off to Ireland to spend time with an Uncle who is quite successful in the movie industry, Suzi experienced a bit of the “high life”. The next stop was to head to the Carribean and spend some time making her living writing music and playing acoustic gigs in restaurants while enjoying life in the sun. For reasons unexplained, she heads north ends up in Montreal teaching swing lessons. In short order, Suzi makes her way back to Kamloops to start her first band, “Suzi Rawn and The Rascalators”.
“King Size Suzi” was born circa 2003. Formed with Matt Wiebe (Bass player from “The Rascalators”), Craig McKay (Drummer and now fiancée) and Jon Treichel (Guitar), the band has toured all over BC and Alberta, and recorded 2 albums. The band has just compiled the top 5 songs from their 2 albums into “Because of Love II”, now available through their website www.KingSizeSuzi.com With deals in the works, Suzi is confident that any record deal will be structured to include her existing bandmates. “Whatever people are interested in making these deals want to see chemistry on the stage. You can't buy that kind of chemistry”.
Then, of course, there's Canadian Idol. If you're not familiar with her huge success finishing fourth in the Canada wide competition, where exactly have you been? I asked Suzi if, knowing what she does now, she would still have chosen to try out for the competition. There's no pause, simply put she'd do it all over again and recommend the experience to anyone who truly loves to sing. Even though her hands are firmly tied until her contract with CTV is completed on December 15th, her feelings are that the Idol's are very well treated, even spoiled.
When she left Kamloops to try out for the show, Suzi's plan was to surrender herself to the situation. She was able to outperform her own expectations. When she looks back on her various performances, Minnie the Moocher stands out as the most comfortable and enjoyable effort. The hardest part of being on Canadian Idol was trying to relax and enjoy the experience. Besides learning tons of information about music industry and gaining some top quality vocal training, Suzi shares her feelings of huge personal growth through the competition. There was no need for her to mention the benefits of huge national exposure!
Thinking where her music career will take her next, Suzi's excitement is obvious. I sense no frustration at having to wait awhile before setting out on the next stage of her career. Suzi is happy to have some time back home with her 2 year old daughter her family and her friends. The time until the CTV contract expires has been filled with opportunities for King Size Suzi to perform at various charity events, clearly showing Suzi's love to perform and her desire to share some of the great karma she received from the Kamloops community.
The great deserts of the world account for millions of square kilometres of essentially useless real estate. Millions of square kilometres of sand that grows larger every year.
So I find myself wondering, on occasion, what would be the effect of creating a huge pipeline from one of the coastal areas, and pumping billions of litres of water into the center of the desert? I don't know anything about the topography of the Sahara. I'm not sure what effect, other than an instant beach, billions of litres of seawater would have on all that sand. Would it create a huge saltwater lake, an inland sea or a saltwater river? Would it all get soaked up in the sand and reduce the dust or sandstorms?
I'm sure the cost would be huge. It would be quite an undertaking, but would the cost even compare the the monies we invest in the extraction and processing and transportation of crude oil? Surely there would be a huge environmental impact, would it be a benefit to the world?
Something to think about.
We've all heard about the Kyoto Accord. We've seen and heard the commercials asking us to reduce our household CO2 emmissions. It seems the major contributors to our fossil fuel use at home are transportation and heating. It seems sensible to consider that heating could well include heating of food.
Tonight my wife and I took my step brother out to "Oriental Gardens"; a restaurant that specializes in both Chinese and Japanese food. If there's one thing I love about Chinese and Japanese food, is that there's always a lot of delicious sounding dishes listed on the menu. We dined in one of those special private rooms, which ended up being a great choice as the kids were nicely contained.
We proceeded to order all manner of foods. Egg rolls, sweet & sour pork ribs, almond chicken, some sushi and on my insistence, a nice array of sashimi. The food was fast and delicious. At first we thought we had ordered far too much. Well, by the end of the affair, there was a modest bag left for lunch the next day.
I got to thinking about CO2 emissions. It seems to me, sashimi might just be an ideal food choice if one should desire to reduce their greenhouse gas emmissions. Fish can be caught without big gas guzzling boats. If you're near the water, it can be transported fairly efficiently. No cooking means no fuel for heating. So I wonder, if the world en mass suddenly took a liking to sashimi, would we be able to make any notable progress in the quest for a greener world?
Whether or not there was any environmental savings, the food was delicious and the company enjoyable.