MATLAB: Black and white image

blackgraygrayscaleimage processingrgbwhite

Hello every one, i want to ask two similar things

1.If image is pure black and white matlab should tell me that image is pure black & white and if grayscale it should tell that its grayscale.

2.in my grayscale image if some pure black or white part come it should save it an array and other gray scale values should be saved in another array. i am attaching a black& white image for reference. Thanks

Best Answer

Try this

[counts, grayLevels] = imhist(grayImage, 256);
if sum(counts(2:end-1)) > 0
  % It's not pure black and white
end
% Get map of non-0 and non-255 pixels
grayPixels = grayImage > 0 & grayImage < 255;
% Get pure black and white image
bw = grayImage; % Initialize

bw(grayPixels) = 0; % Zero out any gray pixels.
% Get gray pixels only
grayOnly = grayImage; % Initialize
grayOnly(~grayPixels) = 0; % Zero out any pure 0 or pure 255 pixels.

Related Solutions

MATLAB: How to put or replace color in rgb/greyscale picture

Try this:

rgbImage = imread('image.jpeg');
subplot(2, 1, 1);
imshow(rgbImage);
% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
% Get the yellow mask
yellowMask = redChannel > 128 & greenChannel > 128;
% Get the white mask
whiteMask = redChannel > 128 & greenChannel > 128 & blueChannel > 128;
% Make yellow mask green
redChannel(yellowMask) = 0;
greenChannel(yellowMask) = 255;
blueChannel(yellowMask) = 0;
% Make the white mask blue
redChannel(whiteMask) = 0;
greenChannel(whiteMask) = 0;
blueChannel(whiteMask) = 255;
% Recombine separate color channels into a single, true color RGB image.
rgbImage2 = cat(3, redChannel, greenChannel, blueChannel);
subplot(2, 1, 2);
imshow(rgbImage2);

MATLAB: Why do not white pixels equal black pixels

Both your assumptions and your code are wrong. The pixels are not exclusively black or white, because there are also many many gray pixels in that image:

>> I = imread('photo.jpg');
>> U = unique(I(:));
>> H = histc(I(:),U);
>> [uint32(U),H]
ans =
           0        6000
           1      234000
          54        1200
         253        1200
         254        1200
         255      236400

The first column shows the RGB value, and the second column shows how many occurrences of each value are in that image.

This is a good example of how beginners often have some belief about what code is doing. But they do not bother to actually check. Code does not care is in your head, nor what you imagine it to be doing. Your job is to check what it is actually doing. Just because you imagine that all pixels are exactly black or white does not mean that they are. And any code that made that assumption would be pretty awful code!

Best Answer

Related Solutions

MATLAB: How to put or replace color in rgb/greyscale picture

MATLAB: Why do not white pixels equal black pixels

Related Question