How to convert DICOM image to JPEG/PNG with out loosing it's metadata?

I need to convert my dicom image to jpg or png format without loosing it's meta data,I have already refered this link,but the solution given on that link is not working at all,cannot save the image as jpg. Please suggest some links or code to this conversion.

[ismail tepedag]

try below trick

b=mat2gray(output_image);

d=im2uint8(b);

new image is d without loosing much details...

Answer 1

[Gopichandh Danala]

    % code
% 793 is a dicom image
DICOM_image = dicomread('793');
info = dicominfo('793');
window_center = info.WindowCenter;
window_width = info.WindowWidth;
rescale_slope = info.RescaleSlope;
rescale_intercept = info.RescaleIntercept;
low = abs(info.RescaleIntercept)-abs(info.WindowCenter)+30;
high = low+info.WindowWidth;
figure, imshow(DICOM_image, [low high]);
[nrows, ncols] = size(DICOM_image);
output_image = zeros(size(DICOM_image));
new_image = zeros(nrows, ncols);
max_pixel_intensity = 255;
for i = 1:nrows
    for j = 1:ncols
        new_image(i, j) = DICOM_image(i, j) * rescale_slope + rescale_intercept;
        if (new_image(i, j) < (window_center - window_width / 2))
            output_image(i, j) = 0;
        else if (new_image(i, j) > (window_center + window_width / 2))
                output_image(i, j) = max_pixel_intensity;
            else
                output_image (i, j) = (max_pixel_intensity / window_width) * (new_image(i, j) + window_width / 2 - window_center);
            end
        end
    end
end
output_image = uint8(output_image);
figure, imshow(output_image);
imwrite(output_image,'converted.jpg');

Hope it helps, Let me Know

[Suba Suba]

Thank you for the answer,but it's giving an error like this

??? Reference to non-existent field 'RescaleSlope'.

Error in ==> Untitled5 at 7
rescale_slope = info.RescaleSlope;

[Walter Roberson]

Different dicom images need different metadata headers. RescaleSlope does not happen to be one of the mandatory fields.

Whatever solution you come up with needs to account not only for public dicom fields with well known names; it also has to account for private dicom fields whose interpretation you do not know. Oh and remember that there are several thousand public fields so if you want to encode them as character you may need to know the interpretation of all of them.

I really have to question the wisdom of converting dicom to jpeg or png "without loss of metadata". It is not very practical and it is not very useful.

[Walter Roberson]

Note: the kmeans algorithm has absolutely no use for the DICOM metadata.

However, if it turned out that your original pixels were not square (unusual but theoretically possible), then you would need to be careful in your distance algorithm. If you wanted to be robust enough to protect against that, it is possible to figure out the pixel spacing. See https://www.mathworks.com/matlabcentral/answers/215612-how-can-i-convert-pixels-to-mm-for-a-specific-dicom-image#answer_178301

[Suba Suba]

yea,I dont need DICOM data for the k means algorithm,but I need it to calcualte the size of pixels later.

[Walter Roberson]

Just extract the PixelSpacing DICOM information and save that, rather than trying to save all of the metadata .

[Suba Suba]

Yea,Okey.Thank you.

[ismail tepedag]

1. What is 30 ? it works but why ?

low = abs(info.RescaleIntercept)-abs(info.WindowCenter)+30;

2. +window_width/2 shall not be existing in below code.

output_image (i, j) = (max_pixel_intensity / window_width) * (new_image(i, j) + window_width / 2 - window_center);

Have nice day !

Answer 2

[Walter Roberson]

It is not possible to convert DICOM to JPG or PNG without losing metadata.

For JPEG files you could convert convert the metadata to some kind of string encoding, and then include it in the file as an EXIF "Description" field, provided that the encoding of the metadata does not occupy more than 64 Kb; see https://en.wikipedia.org/wiki/Exif

PNG does not have EXIF. You can, though, encode arbitrary metadata as name=value strings; see http://stackoverflow.com/questions/9542359/does-png-contain-exif-data-like-jpg -- or at least you could in theory, as imwrite() does not support that. You could, though, instead use the same technique as described above, encoding the metadata as strings (somehow) and then use imwrite() to PNG with the 'Description' name/value pair.

Working out how to convert all of the metadata to strings that could later be parsed would be up to you.

[Suba Suba]

Thank you for the useful links and information, I will refer those links.