How to count the number of pixels from an image for specifies colors?

Question

Jotheeshwar V 2018-7-4

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/408785-how-to-count-the-number-of-pixels-from-an-image-for-specifies-colors

编辑： Jan 2019-6-11

I have used the code stated below.

if true
  % code
imread color.jpg
load color.jpg
redChannel = color(:, :, 1);
greenChannel = color(:, :, 2);
blueChannel = color(:, :, 3);
whitePixels = redChannel    == 255 & ...
            greenChannel  == 255 & ...
            blueChannel   == 255; 
count = sum(whitePixels(:));
Red1Pixels = redChannel    == 255 & ...
            greenChannel  == 166 & ...
            blueChannel   == 166;
count = sum(Red1Pixels(:));
Red2Pixels = redChannel    == 254 & ...
            greenChannel  == 85 & ...
            blueChannel   == 82; 
count = sum(Red2Pixels(:))
Blue1Pixels = redChannel    == 179 & ...
            greenChannel  == 169 & ...
            blueChannel   == 250; 
count = sum(Blue1Pixels(:))
Blue2Pixels = redChannel    == 255 & ...
            greenChannel  == 255 & ...
            blueChannel   == 255; 
count = sum(Blue2Pixels(:))
end

and I am getting error as below.

if true
  % code
Index exceeds matrix dimensions.

Error in Try_03_07_2018 (line 17) greenChannel = color(:, :, 2); and Try_03_07_2018 is the file name.

Kindly help me out of this.

Regards,

Jotheeshwar V

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Answer 1

Jan 2018-7-4

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/408785-how-to-count-the-number-of-pixels-from-an-image-for-specifies-colors#answer_327475

编辑：Jan 2018-7-4

在 MATLAB Online 中打开

Neither

imread color.jpg

nor

load color.jpg

import the pixels of the image to th variable color. Use this instead:

color = imread('color.jpg');

By the way: I'd expect load color.jpg to show an error already. So are you sure that your code run at all?

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Image Analyst 2018-7-5

Did you try my answer below???

Jotheeshwar V 2018-7-5

Yes, It worked out. Thanks a lot

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Answer 2

Image Analyst 2018-7-4

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/408785-how-to-count-the-number-of-pixels-from-an-image-for-specifies-colors#answer_327482

在 MATLAB Online 中打开

Replace this

imread color.jpg
load color.jpg

with this

fileName = fullfile(pwd, 'color.jpg');
color = imread(fileName );
[rows, columns, numberOfColorChannels] = size(color);
if numberOfColorChannels < 3
    errorMessage = sprintf('%s is not a color image!', fileName)
    uiwait(errordlg(errorMessage));
    return;
end

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Answer 3

komal 2019-6-7

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/408785-how-to-count-the-number-of-pixels-from-an-image-for-specifies-colors#answer_378217

After doing skin detection. I want to count the pixels of white region which indicates skin part shown in the image.How can I do it? Please help me out

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Image Analyst 2019-6-7

在 MATLAB Online 中打开

numWhitePixels = nnz(skinMask);

where skinMask is your binary image that you get after doing the skin detection (which I assume you already know how to do that part).

Jan 2019-6-11

编辑：Jan 2019-6-11

@komal: Please do no append a new question in the section for answers of another thread. Ask a new question instead.

"Not working" is a lean description of our problem. Please mention any details. Of course you can use nnz to count elements in an array. So if something is not working for you, you have to explain, what the inputs are, what you want to achieve and what you get instead: a result which differs from your expectations, or an error message?

Afert opening a new thread, delete this pseudo answer here. Thanks.

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