MATLAB Answers

array size notation


I have a doubt in working with Images. An image is represented in MATLAB in the form of row multiplied with columns.

3D image has been represented as for e.g., 256 * 208 *2...

In the above example, 256 indicates rows. 208 indicates columns..

Could you tell me 2 indicates what factor exactly.

Could you explain the same concept for 4D images also.

Thanks & Regards,





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2 Answers

Answer by Jan Simon
on 24 Mar 2012
 Accepted answer

The rows and columns are not multiplied. "256 * 208 * 2" means, that the array has the dimensions [256, 208, 2]. The trailing 2 could mean, that each pixel of a 2D plane has 2 color components, e.g. hue and saturation or red and blue. Or the first component can be the Z-value, while the second one is the grey level.

There is no standard definition for 4D images (as there is no for 3D images). It could be a movie, when the 4th component is the time and the first 3 components are RGB images.

Is it clearer now? The numbers are not factors, but the dimension of a kind of table.


Hi Jan, Thanks for your reply. consider the following. You are standing. a train is running on your background. Now i am capturing this situation.

Whether the obtained image is a 4D image.

Regards. Siva


Jan Simon
on 27 Mar 2012

I do not understand the statement. Is this a question? Do you want to know, if this situation can be represented as 4D array? If so, it depends on what you call "capturing". Taking a movie on tape means discrete 5D data usually: 2D matrix of [1x3] RGB value, one for each frame, plus sound. On the other hand these data are stored sequentially on the tape, so you actually have an 1D data stream...

capturing means, just a still image. not a video

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