MATLAB: Wrong pixel color when save figure as pdf using a different background color

Question

When I function imshow to display an image and change the default color, everything is okay. However, when I save the figure to pdf format, the color of white pixel is not correct.

set(groot, 'DefaultFigureColor', 'blue');
set(groot, 'DefaultFigureInvertHardcopy', 'off');
p = phantom();
figure(1)
imshow(p)
saveas(gcf, 'phantom.pdf');

This is the result of Figure 1.

This is the result in file 'phantom.pdf'.

Answer 1

The cause is that renderer we use to print is switched to painters. You may use -opengl flag with print command

print(gcf, 'phantom', '-dpdf', '-opengl')