How to change the range of histogram?

[Mohd Farhan]

hello,

actually i want to change the range of gray scale image histogram...
i.e. let suppose i divide gray scale histogram in 4 parts: from 0-75, 76-150, 151-200, 201-255.
Now i want to allot new range for all the four new sub-histograms i.e. let suppose..
for 0-75 --> i want to scale it in new range from 0-100.
for 76-150 --> i want to scale it in new range from 50-150.
for 151-200 --> i want to scale it in new range from 100-200.
for 210-255 --> i want to scale it in new range from 50-240.
AND AFTER THAT I WANT TO SEE INDIVIDUAL imhist OF ALL THE FOUR NEW SCALED SUB-HISTOGRAMS.

^^ HOW CAN I DO THIS?

PLEASE HELP ME OUT.

[Nasser M. Abbasi]

Is this what called histogram equalization? if so, help histeq,
and see code at Matlab central for this.

if not, may be someone else can help.

--Nasser

[Learner]

"Nasser M. Abbasi" <n...@12000.org> wrote in message

> Is this what called histogram equalization? if so, help histeq,
> and see code at Matlab central for this.
>
> if not, may be someone else can help.
>
> --Nasser

it is not histogram equalization.. it is different thing.

[Godzilla]

"Learner" wrote in message <jdk1ic$n9b$1...@newscl01ah.mathworks.com>...

It seems that you just want to change the tick marks on the histogram plot.

[ImageAnalyst]

Mohd:
You want linspace to create the new range, and intlut to remap the
gray levels. This is NOT histogram equalization. See this demo:

% by ImageAnalyst
% IMPORTANT: The newsreader may break long lines into multiple lines.
% Be sure to join any long lines that got split into multiple single
lines.
% These can be found by the red lines on the left side of your
% text editor, which indicate syntax errors, or else just run the
% code and it will stop at the split lines with an error.
clc; % Clear the command window.
close all; % Close all figures (except those of imtool.)
clearvars; % Erase all existing variables.
workspace; % Make sure the workspace panel is showing.
fontSize = 16;
% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
baseFileName = 'cameraman.tif';
fullFileName = fullfile(folder, baseFileName);
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
% Didn't find it there. Check the search path for it.
fullFileName = baseFileName; % No path this time.
if ~exist(fullFileName, 'file')
% Still didn't find it. Alert user.
errorMessage = sprintf('Error: %s does not exist.', fullFileName);
uiwait(warndlg(errorMessage));
return;
end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image. numberOfColorBands should be = 1.
[rows columns numberOfColorBands] = size(grayImage);
% Display the original gray scale image.
subplot(3, 2, 1);
imshow(grayImage, []);
title('Original Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off')

% Let's compute and display the histogram.
[pixelCount grayLevels] = imhist(grayImage);
subplot(3, 2, 2);
bar(pixelCount);
title('Histogram of original image', 'FontSize', fontSize);
xlim([0 grayLevels(end)]); % Scale x axis manually.

% for 0-75 --> i want to scale it in new range from 0-100.
% for 76-150 --> i want to scale it in new range from 50-150.
% for 151-200 --> i want to scale it in new range from 100-200.
% for 210-255 --> i want to scale it in new range from 50-240.
% Create the new mapping using linspace.
lut(1:76) = uint8(linspace(0, 100, 76));
lut(77:151) = uint8(linspace(50,150, 75));
lut(152:201) = uint8(linspace(100, 200, 50));
lut(202:256) = uint8(linspace(50, 240, 55));

% Create the output image using the function intlut().
outputImage = intlut(grayImage, lut);
% Display the output gray scale image.
subplot(3, 2, 3);
imshow(outputImage, []);
title('Output Image', 'FontSize', fontSize);

% Let's compute and display the histogram.
[pixelCount2 grayLevels2] = imhist(outputImage);
subplot(3, 2, 4);
bar(pixelCount);
title('Histogram of output image', 'FontSize', fontSize);
xlim([0 grayLevels2(end)]); % Scale x axis manually.

% Plot each range independently.
% WARNING: Several ranges overlapped and were combined in to the same
range.
% Plot the range 0-100
subplot(3, 4, 9);
bar(0:100, pixelCount2(1:101));
xlim([0 255]);
% Plot the range 50-150
subplot(3, 4, 10);
bar(50:150, pixelCount2(51:151));
xlim([0 255]);
% Plot the range 100-200
subplot(3, 4, 11);
bar(100:200, pixelCount2(101:201));
xlim([0 255]);
% Plot the range 50-240
subplot(3, 4, 12);
bar(50:240, pixelCount2(51:241));
xlim([0 255]);

[Learner]

ImageAnalyst <imagea...@mailinator.com> wrote in message <0d99c30c-1f41-4dd0...@g41g2000yqa.googlegroups.com>...

thnks.. it works..