Gray image quantization

Question

Alan AF 2012-2-10

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https://ww2.mathworks.cn/matlabcentral/answers/28659-gray-image-quantization

编辑： Erik 2013-10-8

I am trying to quantize an image into 12 bit intensity using the below code:

R2D = mat2gray(R2D);             % intensity between [0,1]    Double 
R2D = double(uencode(R2D,12));   % intensity between [0,2^12] integer
PIC = mat2gray(R2D);             % intensity between [0,1]    Double
imshow(pic);

the problem is in 'uencode' function , the input must be in the range of [-1,1], is there a way to do that quantization for input values between [0,1]? may be some changes to the 'uencode' will do job :)

Many thanks

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Answer 1

Alan AF 2012-2-10

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https://ww2.mathworks.cn/matlabcentral/answers/28659-gray-image-quantization#answer_37016

在 MATLAB Online 中打开

Thank you, I found the Solution:

R2D = mat2gray(R2D);
[R2D8,map] = gray2ind(R2D,128); 
pic = ind2gray(R2D8,map);
pic = mat2gray(pic);
imshow(pic);

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Image Analyst 2012-2-10

This does 128 gray levels, not 4096.

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Answer 2

Image Analyst 2012-2-10

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https://ww2.mathworks.cn/matlabcentral/answers/28659-gray-image-quantization#answer_36976

在 MATLAB Online 中打开

How about using code like:

actualMin = double(min(min(imgOriginal)));
actualMax = double(max(max(imgOriginal)));
slope = (desiredMax - desiredMin) / (double(actualMax) - double(actualMin));
scaledImage = slope * (double(imgOriginal) - actualMin) + desiredMin;

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Alan AF 2012-2-10

Thanks for your reply

Actually my intention is to Quantize the Image (i.e store every pixel into an 12 bit integer), is there a way to do that?

many thanks :)

Image Analyst 2012-2-10

I didn't think that was your intention because at the end you called mat2gray() which forces it into a 0-1 range, which pretty much wipes out quantization - not quite but for most intents and purposes it does. And the quantized intermediate images, you didn't do anything with.

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