How from uint8 to 0 and 1?

I import the following image which is a [583x673x3] uint8 :

and i would like the convert the grey/black color to origianally black.How it can be ?

Answer 1

[Sean de Wolski]

Igray = rgb2gray(I);
BW = im2bw(Igray,graythresh(Igray));
imshow(BW)

[Image Analyst]

grayImage = uint8(255 * BW);

[Dimitrios]

Sorry i deleted the question,because i found it.but thanks for the answer.For others my question was 'How to convert the resulted image again to uint8?'

Answer 2

[Youssef Khmou]

    rgb2gray(im2double(X));

[Dimitrios]

thank you for your answer, but the image remained the same.

Answer 3

[Chad Greene]

Tinker with this threshold value:

threshold = 250; 
A = imread('export_fig_out.png');
A(A>=threshold)=255;
A(A<threshold)=0;
imshow(A)

[Chad Greene]

Before adjusting the image, (if you have the image processing toolbox) try imhist(A) to see where values in A lie relative to the gray scale.

[Sean de Wolski]

graythresh separates modes for you :)