Steve on Image Processing

April 7th, 2006

All about pixel colors: Summary

This week I wrote the last in a series of postings that discussed how MATLAB associates matrix values with specific screen pixel colors. The series talked about the two fundamental image display models (indexed and truecolor); the scaled indexed image variation; using indexed scaling to program brightness/contrast controls; and the grayscale and binary image conventions in the Image Processing Toolbox.

For easy reference, here is the entire series:

  1. Introduction
  2. Truecolor and indexed images
  3. Scaled indexed images
  4. Window-level and CLim
  5. Reference information
  6. Grayscale and binary images

[Updated 10-April-2006 to add link to the reference information post.]

By Steve Eddins

07:00 UTC | Posted in Pixel colors | Permalink |

You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

29 Responses to “All about pixel colors: Summary”

  1. KOFFI Anderson replied on May 26th, 2006 at 10:08 UTC :

    I’m a student and I’d like to learn more in image processing especially images acquisition by CCD Camera

  2. Steve replied on June 2nd, 2006 at 09:53 UTC :

    Koffi - your question is a little vague, but for camera acquisition I’d point you to the Image Acquisition Toolbox.

  3. Koffi Anderson replied on July 3rd, 2006 at 06:34 UTC :

    I read your tutorial “laser tracking”;I’d like to know more about the calibration process (algorithm) and the util_findlaser(acquResults).thank you

  4. Steve replied on July 5th, 2006 at 07:45 UTC :

    Koffi - I didn’t write the laser tracking demo, and I’m not that familiar with the Image Acquisition Toolbox. There is a lot of information about the product available here: http://www.mathworks.com/products/imaq/

  5. el sawda replied on July 24th, 2006 at 05:09 UTC :

    informations

  6. pritam replied on August 31st, 2006 at 04:10 UTC :

    digital image processing using matlab.

  7. Prerit replied on November 11th, 2006 at 05:00 UTC :

    I am on an project with jpeg 2000 being a part of it.Can you please guide me in making a jpeg 2000 code in matlab- what are the things i need to look for. Or do you have any matlab code for jpeg 2000 where i can actually see what kind of things i need to add more in that in accordance of my work.

  8. Steve replied on November 13th, 2006 at 07:36 UTC :

    Prerit - There is JPEG 2000 code in the book Digital Image Processing Using MATLAB.

  9. taoufik replied on November 19th, 2006 at 11:20 UTC :

    I need a code Matlab for ebcot algorithm

  10. Steve replied on November 20th, 2006 at 11:39 UTC :

    Taoufik - I don’t accept code requests. See this page.

  11. gopalakrishnaraja replied on December 19th, 2006 at 05:45 UTC :

    I’m a finalyear parttime BE student and also working as development engineer in a color sorting machine manufacturing company.I’d like to learn more in image processing especially images acquisition by CCD Camera

  12. Steve replied on December 26th, 2006 at 10:21 UTC :

    Gopalakrishnaraja - For image processing, you might start with Digital Image Processing by Gonzalez and Woods, or Digital Image Processing Using MATLAB, by Gonzalez, Woods, and Eddins. I don’t know that much about image acquisition, but there is a lot of good information on our web site about the Image Acquisition Toolbox. See this page: http://www.mathworks.com/products/imaq/

  13. Imtnan replied on April 23rd, 2007 at 06:53 UTC :

    Dear Steve,

    I have written code for EBCOT (JPEG2000) for 2D images as well as 3D images in MATLAB.
    But it gives a small diffrence in results when compared to the results of VM 9.0 (Standard JPEG2k) software in bpp values.

    Can you please help me finding out my error? I can send you all the code and files if you say so…….

    Anxiously waiting for your reply……

  14. Steve replied on April 23rd, 2007 at 07:20 UTC :

    Imtnan - I’m sorry, but I won’t be able to help with troubleshooting your code.

  15. Imtnan replied on April 27th, 2007 at 08:53 UTC :

    Thanx anyway Bro!

    Actually in detail nothing was available to me so i thought to contact you….

    Sorry for any waistage of your time

  16. malikireddy replied on June 29th, 2007 at 05:34 UTC :

    Hi ,

    Iam looking for a method or appliance which can connect my PC/Laptop to the Ultrasound machine , can any one throw some light , which hardware i would need for it , and if again needed some interface software or so , apart from drivers for Hardware and so on …actually i just want to connect the Ultrasound machine and must be able to see the live pictures in Matlab environment .So please advise.

    Thanks in advance.

    Regards
    Krishna

  17. khairiah replied on July 9th, 2007 at 04:40 UTC :

    Dear Steve,

    It is possible to use Image Acqusition Toolbox to control on shelf digital camera,especially to preview live image and to grab single frame.

  18. hussain replied on July 9th, 2007 at 07:35 UTC :

    Hi dear
    I am student in Manchester university, pleas I need help in my project to measured the diameter from image ( Used CCD camera to captured image will tool rotating), and find (x,y) coordinate for each line. I write the program in matlab but it not work.

    Pleas help.

    Thank you

    [code deleted—SE]

  19. Steve replied on July 9th, 2007 at 08:22 UTC :

    Khairiah—Yes, if you’re camera is supported. See the Image Acquisition product page for details.

  20. Steve replied on July 9th, 2007 at 08:26 UTC :

    Hussain—I’m sorry, but I can’t help you with debugging your program. Also, a blog comment isn’t the best place for posting a lot of code, so I’m going to delete that part.

  21. khairiah replied on July 9th, 2007 at 21:49 UTC :

    steve,
    how if my camera is not scientific camera and also not firewire type camera but more to commercial type
    digital camera.Ex Digital Still camera Sony DSC -F717.
    It is I must have certain driver in order to use imaq.

  22. B NARSIMHACHARY replied on July 10th, 2007 at 04:39 UTC :

    I Want to know the National and International Experts in Image Processing

  23. Dave T replied on July 17th, 2007 at 15:19 UTC :

    khairiah,

    The Image Acquisition Toolbox does not currently support still image cameras, so you will not be able to interface to your camera using Image Acquisition Toolbox.

    You will have to write code to interface to your camera. The easiest way to do this would be to find an ActiveX control that can communicate with still image cameras and use MATLAB’s ActiveX interface.

  24. Yicong replied on August 10th, 2007 at 13:33 UTC :

    Steve,

    I am working image scrambling in JPEG domain. I am looking the matlab code for JPEG encoding and decoding which can display the compressed result(JPEG image). but I didn’t get it. the matlab code about JPEG compression in your book is only for the algorithm implementation, but how can I display the result of your code?

    Please help.

    Thanks a lot.
    Yicong

  25. Steve replied on August 14th, 2007 at 08:35 UTC :

    Yicong—There are examples showing how to use the code in Chapter 8 of the book. What other information are you looking for?

  26. Abhijit replied on November 13th, 2007 at 01:21 UTC :

    Hi Steve,

    After capturing the color image on the color CCD camera, I would like to find out at each pixel the wavelength. Can you please help me regarding the procedure I should follow in order to determine the wavelength at each pixel.

    Please help. Thanks a lot.

    Abhijit

  27. Steve replied on November 13th, 2007 at 09:53 UTC :

    Abhijit—I’m not sure that your question makes sense. Except for laser light, the light arriving at any particular sensor has a full spectrum of wavelengths, not just one. That spectrum is filtered according to the characteristic color of the sensor (e.g., red, green, or blue), and a single number recorded. Then the numbers for several neighboring single-color sensors (red, green, and blue) are combined in some way to produce a single RGB pixel.

  28. yasotha.l replied on October 7th, 2009 at 18:25 UTC :

    hi
    i’m a student and i would like to know about unique color identication in any image and the place of the pixel position.

  29. Steve replied on October 7th, 2009 at 18:27 UTC :

    Yasotha—What do you mean by unique color identification?

Leave a Reply

Wrap code fragments inside <pre> tags, like this:

<pre class="code">
a = magic(3);
sum(a)
</pre>

If you have a "<" character in your code, either follow it with a space or replace it with "&lt;" (including the semicolon).

About

Steve Eddins manages the Image & Geospatial development team at The MathWorks and coauthored Digital Image Processing Using MATLAB. He writes here about image processing concepts, algorithm implementations, and MATLAB.

Subscribe


Recent Comments

  • Sana: hi steve, could you explain to me how i would be able to use the dir function, to do a loop through a directory...
  • Nishtha: Sir, I have preprocessed the image in following steps: [1] adaptive histogram equalization [2] thresholding...
  • Kristof: I also strongly support the idea. I have just recently bumped into the problem that im2single was not...
  • Steve: David—I’ m glad you found it useful!
  • David Lalejini: I found your example very useful for finding connected nodes in a large set of input pairs. I start...
  • tommy: Dear Steve, I have a question,please if you are kind to help me regarding the accumulator array dimensions of...
  • Steve: Abc—I don’t know how to distinguish the faces. You might try posting your question in the MATLAB...
  • Manju: well if we have a few ovals within each other like in a cell how do we measure the distance from the center...
  • Steve: Manju—What do you mean? How is each region defined?
  • Manju: if we have 2-3 regions within each other how do we measure the regions of each one?

Blog Admin

These postings are the author's and don't necessarily represent the opinions of The MathWorks.