Converting from grayscale to binary image gives error

Hi everybody I convert my image from grayscale to binary image, however, the result is completely black. I attached my code and images. Could you please help me with that?

if true
grayImage=imread('20x.png');
binaryImage = im2bw(grayImage,0.4);
binaryImage = imfill(binaryImage, 'holes');
imshow(binaryImage, []);
end

Answer 1

[jonas]

The threshold (0.4) is too high. Reduce the threshold (to e.g. 0.2) or use imbinarize instead of im2bw (recommended).