How can I change figure edges of a figure created with imshow?

Question

I'm using imshow to create this binary image. When it shows the figure I see a grey background and no edges in the figure. If I save the plot in as .png, I see the background as white and I can't see any edges on the figure. How can I add edges to this plot?

Image as shown by imshow:

Image as saved to PNG:

Answer 1

By default, saved figures have a white background. Ensure that the colors of the saved figure match the colors on the display by setting the InvertHardcopy property of the figure to 'off'.

Example:

A = rand(300, 300) > 0.1;

f = figure();
  f.InvertHardcopy = 'off';
  imshow(A);
  title('Binary Image threshold 0.9');
  saveas(f, 'test.png'); 

gives:

Alternatively, it is possible to set the visibility of the axes in the imshow and make the ticks empty:

A = rand(300, 300) > 0.1;

f = figure();
  iptsetpref('ImshowAxesVisible', 'on');
  imshow(A);
  xticks({});
  yticks({});
  title('Binary Image threshold 0.9');
  saveas(f, 'test.png');

that gives:

Source: Matlab Documentation