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.
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It's been a crazy couple of weeks for my musical interests. First, I released my EP "Free". Second, my press release was distributed throughout the world - a quick search for "Mickael Maddison" in Google, Yahoo, MSN etc. should give you quick access to the text. Third, I was thrilled to have our biggest local newspaper "Kamloops Daily News" paste a nice photo of me on the front page of the paper with a 1/2 page article and huge photo in the entertainment section. So to keep the feeling alive, I spent part of today shooting some footage for the video "Friend".
I've put together the footage I shot for "Friend" today and posted the results as "Unfinished" to my music website. I now have to film the "me" shots and the ending and fit them in. Hopefully this week I can get that done. You can find it at:
A few weeks back, I was working on the footage for "In Her Eyes". The main story for this one requires a fair bit of footage of a female actor, a horse, and the two of them together. I've posted the "me" shots as "Unfinished" for now. I just haven't had much luck getting the actors I need quite yet. You can find it at:
The video for "Drink", which is part of the enhanced CD contents of my EP, can be considered done for now. I do intend to do some polishing of a few rough spots eventually, but for now it's there for the world to see. You can find it at:
The first video, which I shot with my Sony CyberShot still camera, has blown me away with the amount of downloads it's been getting. "When I'm Free" was my first ever attempt at making a music video. Although the picture quality isn't nearly as good as found in the others, it's got a raw edge to it that seems to be attracting attention. I am considering doing a higher quality version at some point, however, this one is also on the EP. You can find it at: http://www.mickaelmaddison.com/When_Im_Free.wmv
I hope to get video's finished up for all the songs on this EP before it's time to start recording my next CD. "Castle On A Cloud" and "Blowing In The Wind" may prove to be quite a challenge, however. I'd LOVE to find someone to do an animated video for the first, and the latter will require a couple, some ocean, and lots of romance-esque footage. Nonetheless, I look forward to the challenge.
It wasn't exactly opening night for the much anticipated "Star Wars Episode III, Revenge of the Sith", but last night my lovely wife and I finally got to the theatre to see this final installment in the series. I'm a child of the 70's, and there's no doubt I love Star Wars.
I've seen all the movies innumerous times. I've enjoyed every one of them. Episode III, however, did not come across nearly as strong as I had expected. I definitely enjoyed the movie, but there was something not right about it. The picture that comes to mind that best describes what I think happened to this movie; The Editors of the movie are in the cutting room surrounded by piles and piles of film that probably should not have been cut out of the final product.
I found that the character development (which rightfully need not have been much), was not done enough. From my seat, the emotions of Anakin as he battled with his temptations, his ethical struggle, and his love for Padme were not explored deeply enough. We could see that he was struggling with his issues with the Jedi Council and his apparent friendship with Palpatine, yet his thoughts did not seem to be spoken well enough to convince me the weight was of such tremendous bearing.
The scene that really convinced me that it must have been an issue of cutting rather than poor acting or directing was near the end where Padme confronts the newly named Darth Vader after he slays the Viceroy and his staff. She flys out, emotions charged, to find out of Obi-Wan speaks the truth and the confrontation is far too short. A woman of such strong will and intelligence would not be so easily discouraged and swayed. She would have been far more insistent, she would have gone much further before she declared him as someone she no longer knew.
I look anxiously forward to the DVD release, in hopes that Mr. Lucas and his team salvaged some of those clippings.
Greetings Music Fans!
A business owner out of Victoria whom I've known many years now, has a website that is of much interest to me. Now that my CD is finished recording, and should arrive completely manufactured and ready for sale anytime now, I've begun the process of finding good places to place the disc for sale. First on my list, supporting a Canadian based website is www.ByteMusic.ca.
This site has been created by the efforts of Eric Cooper and his team at Unibyte (which is now partnered with SilverServers of course), and is a great place for signed and unsigned musicians to sell their cd's online, with very little cost to themselves. All I have to do is send them 5 copies of my CD, and they take care of the rest. When they sell off the CD's, I just send them 5 more. When anyone orders your CD, ByteMusic takes care of the order handling, product shipment, and reports back to you, and of course, you set the price!
ByteMusic is still small, but they've got a good list of musicians on there, and if you're not sure about them, you can listen to "ByteRadio", check out some short clips, or buy a download pack and download individual songs from the artists.