uint8 and double in case of image

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vaishali 2014-11-27

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https://ww2.mathworks.cn/matlabcentral/answers/164457-uint8-and-double-in-case-of-image

编辑： Image Analyst 2014-11-27

Hello

In one of the image encryption method I need to convert an image from uint8 to double. But after converting the whole, image is losing some information only white colour with some coloured dots will appear in that double image. so after the required task how to convert it to original image? please guide..

Thanks

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Answer 1

per isakson 2014-11-27

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Try

        a=imread('lena.jpg');
        imshow(a);
        b=double(a);
        imshow(b/255);

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vaishali 2014-11-27

Thank You Per Isakson..

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Answer 2

Image Analyst 2014-11-27

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Look at the variable in the workspace/variable editor and tell me if there is data loss there. Chances are you're just not displaying it correctly. For double, if it's not in the range o-1, you need to use [] as the second argument in imshow():

imshow(doubleImage, []);

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vaishali 2014-11-27

编辑：per isakson 2014-11-27

在 MATLAB Online 中打开

in workspace the number of elements not changing.but while displaying

    a=imread('lena.jpg');
    imshow(a);
    b=double(a);
    imshow(b,[]);

after converting it to double it is showing blank white background with some dots. if this is the case how to get back original lena?

Image Analyst 2014-11-27

编辑：Image Analyst 2014-11-27

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The badly-named "a" must be a color image. You cannot display double RGB images unless they're in the range 0-1. You must cast to uint8 first. And since it's color, you won't need the [] - it will ignore them.

imshow(uint8(b));

Or you can divide your array by 255 (which is intmax('uint8')) like per showed.

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