Problem with grayscale image

When I try to开发者_开发问答 show a grayscale image using :

Img = imread('tr2.png');

subplot(111);

imshow(Img);

it does not appear as the original image. Where is the problem ?

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Try to read colormap together with the image:

[Img, map] = imread('tr2.png');
imshow(Img,map);

EDIT:

I believe you have indexed image and you have to convert it to RGB before any processing. Use ind2rgb or ind2gray function.

See for example Steve's blog on indexed images.

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code to get the grayscale:

Img = imread('tr2.png');
gray=rgb2gray(Img);
imshow(gray);

(Matlab)