How to binarize this image?

hi, I have a code :

image=imread('guava.jpg');
figure
imshow(image)
imR1=image(:,:,1);
imG1=image(:,:,2);
imB1=image(:,:,3);
gray = uint8(0.299*double(imR1) + 0.587*double(imG1) + 0.114*double(imB1));
%opening operation
di = strel('line',50,100);
dilate = imdilate(gray,di);
er = strel('line',50,100);
erode = imerode(dilate,er);
%difference image between opening operation and grayscale
difference_image = double(gray) - double(erode);
figure; % Open up another figure window.
subplot (2,2,1)
imshow(dilate)
subplot (2,2,2)
imshow(erode)
subplot(2,2,3)
imshow(difference_image, []); % Display the difference image.
outputImage = uint8(255 * mat2gray(difference_image));
figure
imshow(outputImage)

the result is like :

I need to transform that image into this one :

they said "convert to binary image". I tried with imbinarize and im2bw, the result is all white. what should I do to get that binary image?

[Walter Roberson]

Can you provide the original image?

[Nanda Sulthan Estupratama]

sure

that's the original image

Answer 1

[Image Analyst]

The image you show is more like a gray scale image. To get a binary image, do this:

rgbImage = imread('original2.PNG');
binaryImage = rgbImage(:,:,1) < 200;
imshow(binaryImage);

[Nanda Sulthan Estupratama]

but it says binary image. then, if I have this image:

what should I do to transform that image into this one :

[Walter Roberson]

Zhiyu Xiao comments to Nanda Sulthan Estupratama:

This is a really important question whose answer can be applied to many other things.

[Image Analyst]

It looks like you can just pass Nanda's original low contrast image into imadjust() to get an image with increased contrast.