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Dear ImageJ Experts,
If I have sent this message twice please pardon me, because my first post has "This post has NOT been accepted by the mailing list yet." on the top. I want to apply an IR filter on a color image. And so was exploring different tools to accomplish this task. I am new to ImageJ and have very less knowledge about the programming possibilities. I would like to know whether it is possible to apply an IR filter of a specific wavelength on a RGB image or some other desired wavelength filter (from the visible spectrum) on a RGB image? If so, please guide me. Thanks in advance! :) Best Regards, Nisha -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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On 1/14/2013 11:40 AM, Nisha Shah wrote:
> Dear ImageJ Experts, > > If I have sent this message twice please pardon me, because my first post > has "This post has NOT been accepted by the mailing list yet." on the top. > > I want to apply an IR filter on a color image. And so was exploring > different tools to accomplish this task. I am new to ImageJ and have very > less knowledge about the programming possibilities. > > I would like to know whether it is possible to apply an IR filter of a > specific wavelength on a RGB image or some other desired wavelength filter > (from the visible spectrum) on a RGB image? If so, please guide me. > > Thanks in advance! :) > > Best Regards, > Nisha > > -- > ImageJ mailing list: http://imagej.nih.gov/ij/list.html ... [show rest of quote] First, this is a more complicated question than I think you probably
appreciate. Second, filtering, per se, is typically done at capture time using "hardware" filters. You can do some "software filtering" when you have extremely well defined spectral conditions, but this is rarely the case. Finally, there is the mixed situation where you want to use multiple images with and without a hardware filter to separate a part of a signal. ImageJ has utility in this latter instance. Digital RGB representations of images are typical done either by using a monochrome camera taking pictures using a spectral filter placed in front of the camera to limit the wavelengths captured, or by using a color camera in which case the channels are most often separated by what is know as a Bayer filter. The spectral sensitivity of the monochrome chip can vary in either case. Some cameras have the ability to turn on and turn off an "IR " filter, and if you have such a camera, you might be able to determine the IR contribution to the image by image subtraction. ImageJ could help you with this task depending on whether the IR filter is a lowpass or bandpass filter. ImageJ certainly can do mathematical operations on sets of images like image subtractions. You do not tell us enough about the hardware part of your task to tell you much more about how ImageJ might help. Rob Baer -- __________________ Robert W. Baer, Ph.D. Professor of Physiology Kirksille College of Osteopathic Medicine A. T. Still University of Health Sciences Kirksville, MO 63501 USA -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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Dear Dr. Baer,
I am extremely sorry, I made a huge mistake in explaining my doubt. Actually, I have a color image (captured from an ordinary camera) on which I want to produce an effect as if during the time of capture, the object was exposed to some wavelength. For example, while capturing an image, say the object was exposed with a wavelength of 630nm (red color) or an infrared wavelength. I want to induce such effects on images. I am really sorry, I used wrong words in expressing my doubt. Thanks in advance! Nisha |
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On Monday 14 Jan 2013 18:36:39 you wrote:
> Actually, I have a color image (captured from an ordinary camera) on which I > want to produce an effect as if during the time of capture, the object was > exposed to some wavelength. No you can't achieve that on an image that has already been captured because you do not know which parts of the image reflect or absorb IR light. Digital cameras typically have an infrared blocking filter because the sensors usually respond to the near infrared as well as in the visible spectrum. That being said, a tiny amount of near infrared light gets in the camera and gets mixed with the visible light, and this can be captured if you use a visible light blocking filter like the Hoya R72 or the Wratten 89B (you can get these filters in photographic equipment shops). But you can't really separate the NIR light from the rest of the image once it is shot. Some people remove the IR blocking filter from the camera to have more sensitivity in the NIR, but this is not something you may want to do with an expensive camera. With some webcams this can be done very easily. See for example: http://www.hoagieshouse.com/IR/ Regards Gabriel -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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In reply to this post by nisha
On 1/14/2013 12:36 PM, nisha wrote:
> Dear Dr. Baer, > > I am extremely sorry, I made a huge mistake in explaining my doubt. > Actually, I have a color image (captured from an ordinary camera) on which I > want to produce an effect as if during the time of capture, the object was > exposed to some wavelength. For example, while capturing an image, say the > object was exposed with a wavelength of 630nm (red color) or an infrared > wavelength. > > I want to induce such effects on images. I am really sorry, I used wrong > words in expressing my doubt. > > Thanks in advance! > > Nisha > > ... [show rest of quote] Perhaps I am still missing your question, but let me try saying it this
way. In "theory" an RGB color image contains only information from the visible part of the spectrum and NO information about infrared emission. Depending on the physical collection method, however, this theoretical assumption may not be the case. I imagine you are concerned that your images contain influence from IR emissions. However, you can not estimate how much IR contamination there is in your images with software alone (ImageJ or any other software). To estimate IR contamination you must also make direct, physical measurement of IR cross-talk under conditions where there is no primary image signal . Such crosstalk may vary with conditions (say excitation intensity), and so it must be measured under conditions appropriate to you measure. That is, you need appropriate positive and negative controls for IR crosstalk. The only way to know how much contamination of your images comes from IR emissions is to measure IR crosstalk physically. If you construct some sort of library specifying how much IR emissions affects each of your RGB channels, you may THEN be able to subtract out its effect. You CANNOT estimate how much IR has contributed to your sample images from just the images. Hope this makes the issue more clear, Rob Baer -- __________________ Robert W. Baer, Ph.D. Professor of Physiology Kirksille College of Osteopathic Medicine A. T. Still University of Health Sciences Kirksville, MO 63501 USA -- ImageJ mailing list: http://imagej.nih.gov/ij/list.html |
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