what is the meaning of "order of grey level" in an image?

Hello all, I am new to Image processing so i am trying to get hold of basics. After a lot of search i was able to find how to determine number of grey levels in an image. Now i am stuck with "order of grey levels". Can any one help in understanding order of grey levels? any help is appreciated.

Answer 1

[Image Analyst]

Never heard of it. Perhaps it has to do with sorting. Some functions need the gray levels to be sorted like medfilt2() and ordfilt2(), and they do that internally. You'd need to figure out what the author meant from the context of the entire paragraph or article.

The number of gray levels in an image needs you to define it. What if an image is uint8 (256 possible gray levels) and has pixels with all gray levels except 0. What is its "number of gray levels"? Is it 256 or 255? It just depends on how you define it and what you want to do with that information.

[Dinesh Kumar R]

You are right Image Analyst its about sorting grey values.The following is the paragraph:

" This method uses a simple chromosome structure. An example of the chromosome structure has been shown in Fig. 1. This structure uses a sorted array of random integer numbers. The size of each chromosome is equal to n, where n represents the number of gray levels in the input image. In the proposed structure, the indices indicate the order of gray levels in the image, for example the index 1 indicates the first gray level in the image and so on. In Fig. 1, the first gray level in the image is 0, the second one is 25, the third one is 40, and the last one is 255. In remapping, the first gray level in original image is replaced with the value of first gen of chromosome and so on._"

I have attached the image </matlabcentral/answers/uploaded_files/44968/array.png>

As far as my understanding, number of grey levels is 2^(no.of.bits per pixels[bpp]) if we take bpp to be 8 then we have 256 greylevels ranging from [0-255]. Can you please justify why are you saying "except 0".

can you please elaborate on this instance a bit? I am so confused. Please help me.