MATLAB Answers

image conversion


When the input image is of dimension 256 256 3..... I will use the command rgb2gray to make it as 2D image to work it out. Whether this procedure is correct?




Are you trying to convert a color image into a black and white image?

Thanks for writing Daniel. Sometimes I will have gray image with the dimension i mentioned earlier. Some commands does not accept 3D.. So, i will be changing.

3 Answers

Answer by Junaid
on 10 Apr 2012

yes, you can convert color image to gray scale image, and gray scale image is 2-D image.


on 10 Apr 2012

many image processing algorithm work on gray scale image(2-D) image, in case you want to do it in loop then do it like this

if size(img,3) >1
img = rgb2gray(img);

Where size(img,3) will return you the number of channels ( 1 means 2-D image and more then values indicates higher channels.)

thanks Baber. I will take your points.

You may be interested in image conversion sdk in .NET,feature of Convert image among Binary (1-bit), Gray Scale, RGB etc.Automatically detect source image & document format .check it

Answer by Image Analyst
on 10 Apr 2012

Yes, you can do that, though it is often not the way to get the best possible gray scale image. You can do this:

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
grayImage = rgb2gray(rgbImage);

and use imshow on each of those to find out which gives you the best contrast, or whatever it is that you think would give you the best image. Or even better, use Principal Components Analysis (PCA) to find out the best combination of those color channels to give you the combination to get you a good signal along the optimal direction in the 3D color gamut space.

Or even better is to show us your image and tell us what you want to measure or enhance in the image. Perhaps you don't want to throw away all your color information at all. Maybe you can use the color information to your advantage. I can't tell unless I see your image. I do this stuff all day for a living, as you might guess from my icon.

  1 Comment

Thanks Image Analyst. I know your profession well. Thatsy Sometimes I used to post my doubts mentioning your name itself.

Hi Friends, I Thank all for replying my doubt.


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