Quantizing colour planes using 4-bits

Hi,

First, I want to mention that I'm not in an attempt of doing a homework from my question here :-)

If I was required to *quantize* the colour planes of an image using 4-bits:

- What does this statement mean?

- How can I perform this in matlab?

Thanks.

Answer 1

[Image Analyst]

Refer to here: http://en.wikipedia.org/wiki/Color_quantization

[med-sweng]

@Image Analyst. Thanks for your reply. How can I quantize using 4-bits using matlab?

[Image Analyst]

One way (not necessarily the best) is to just divide each color plane by 16. Of course it's still taking up 8 bits if you keep it in a uint8 variable. There are no 4 bit variables so you'll have to pack them together somehow if you really want 4 bits on disk.

[med-sweng]

@Image Analyst. I found that there is a method called *imquantize*. I used it this way:

>> quan = imquantize(im,16);

But, I got the following error:

??? Undefined function or method 'imquantize' for input arguments of type 'unit8'

How can I go around this?

Thanks.

[Image Analyst]

I can use that function with no problem. What does this say?

>> which imquantize

I think you don't have it. You have an old version probably.

[Walter Roberson]

Or you might not have that toolbox.

[Image Analyst]

Type ver on the command line to find out what toolboxes you have installed. Tell us what it says (you don't need to tell us your license number though).

[Walter Roberson]

Note: "ver" tells what is installed, not what is licensed.

Answer 2

[Elad]

implement in matlab: http://imageprocessingblog.com/color-reduction-using-k-means-clustering/