Why are my saveas binary images only black?

Dear all,

I have DICOM images, that I convert to binary images and save them into folder. Saving is correct, but these images could be look like that:

but these images look like this:

This is my code:

Folder = 'C:/Users/ced0005/DP/DP_framework/DICOM/slicesCT/';
for k = 1:10 figure(k); 
    for p = 48:86
  filename = fullfile(Folder, sprintf('%06d.dcm', p));
  grayImage(:,:,1,p - 47)= dicomread(filename);
  grayImage_pater(:,:,1,p - 47)= dicomread(filename);
  [rows, columns, numberOfColorChannels] = size(grayImage);
if numberOfColorChannels > 1
  % Máme barevný obraz, musíme ho převést na černobílý = vybereme zelený kanál
  grayImage = grayImage(:, :, 2); % zelený kanál
end
eq_grayImage = histeq(grayImage);%ekvalizace pomocí histogramu obrazu
[rows, columns, numberOfColorChannels] = size(grayImage_pater);
if numberOfColorChannels > 1
  % Máme barevný obraz, musíme ho převést na černobílý = vybereme zelený kanál
  grayImage_pater = grayImage_pater(:, :, 2); % zelený kanál    
end
eq_grayImage_pater = histeq(grayImage_pater);

thresholdValue = 900;
binaryImage_okoli = grayImage > thresholdValue;
% Odstranění okolí.
binaryImage_okoli = imclearborder(binaryImage_okoli);
% Vyplnění otvorů.
binaryImage_okoli = imfill(binaryImage_okoli, 'holes');
% Vymazání menších otvorů.
binaryImage_okoli = bwareaopen(binaryImage_okoli, 750);

%Roztažení binárního obrazu pro přesnější segmentaci
se = strel('line',5,100);
binaryImage_okoli= imdilate(binaryImage_okoli,se);
    imshow(binaryImage_okoli); 
    temp=['fig',num2str(k),'.png']; 
    saveas(gca,temp); 
    end
end

Can you advise me? Please, some simple solution. Thank you for your answers.

Answer 1

[Image Analyst]

The graylevel is only 1 so you can't see it. Multiply it by 255 if you want it to be a uint8 image where the "true" pixels show up as white.

[Veronika]

I tried multiply image according to you like this:

Folder = 'C:/Users/ced0005/DP/DP_framework/DICOM/slicesCT/';
for k = 1:10 figure(k); 
    for p = 48:86
  filename = fullfile(Folder, sprintf('%06d.dcm', p));
  grayImage(:,:,1,p - 47)= dicomread(filename);
  grayImage_pater(:,:,1,p - 47)= dicomread(filename);
  [rows, columns, numberOfColorChannels] = size(grayImage);
if numberOfColorChannels > 1
  % Máme barevný obraz, musíme ho převést na černobílý = vybereme zelený kanál
  grayImage = grayImage(:, :, 2); % zelený kanál
end
eq_grayImage = histeq(grayImage);%ekvalizace pomocí histogramu obrazu
[rows, columns, numberOfColorChannels] = size(grayImage_pater);
if numberOfColorChannels > 1
  % Máme barevný obraz, musíme ho převést na černobílý = vybereme zelený kanál
  grayImage_pater = grayImage_pater(:, :, 2); % zelený kanál    
end
eq_grayImage_pater = histeq(grayImage_pater);

thresholdValue = 900;
binaryImage_okoli = grayImage > thresholdValue;
% Odstranění okolí.
binaryImage_okoli = imclearborder(binaryImage_okoli);
% Vyplnění otvorů.
binaryImage_okoli = imfill(binaryImage_okoli, 'holes');
% Vymazání menších otvorů.
binaryImage_okoli = bwareaopen(binaryImage_okoli, 750);

%Roztažení binárního obrazu pro přesnější segmentaci
se = strel('line',5,100);
binaryImage_okoli= imdilate(binaryImage_okoli,se);
    imshow(binaryImage_okoli); 
uint8Image = uint8(255 * binaryImage_okoli);
     temp=['fig',uint8Image(k),'.png']; 
    saveas(gca,temp); 
    end
end

This is for now my the best output in this problem. But I don´t know, if it´s completely right, because after one for loop there appears black and white image, but after few seconds changes to black. I don´t know, what is exactly saved, because I can´t see these figures anywhere.

[Veronika]

I figured it out, that my saved image is fig (file) and constantly being overwritten and I would like to fig1.png, fig2.png,....fig38.png. Can you advise me, how resolve this?