Colour changes from figure to png upon export

Hi everyone, I am generating a plot using the code below where the lines plotted in the loops are in white and with a width of 0.2, however upon exporting the figure as a png the lines are exported in black. Does anyone know why the colour in the figure is different to the figure in the png

figure(1)

scatter(Table(:,2),Table(:,1),5,Table(:,3))
colormap('gray')
set(gca,'DataAspectRatio',[1 1 1])
set(gca,'fontsize',18)
xtickangle(45)
xlim([0 1800])
ylim([317 715])


for i=1:17
    hold on
    line([1,1800],[i*100,i*100],'Color','white','LineWidth',0.2)
end

for i=0:36
    hold on
    line([i*100,i*100],[0 900],'Color','white','LineWidth',0.2)
end

print(gcf,'Grids2','-dpng','-r1000');

[DGM]

I can't seem to replicate the issue. For me, in R2019b, it exports with white lines.

The image is large (about 6000x7000px), so some viewers may be causing issues with nearest-neighbor display interpolation, so some features tend to disappear at most zoom levels. Still, that shouldn't be adding black lines.

Answer 1

[DGM]

I'm going to go out on a limb and guess that you're setting the axes color to something other than white.

set(gca,'color','r') % something like this?

Otherwise, the white grid would be invisible. If that's the case, then this may help:

https://www.mathworks.com/matlabcentral/answers/100905-why-does-my-figure-print-with-a-white-background-and-white-axes-even-though-i-have-set-the-axes-and

set(gcf, 'InvertHardcopy', 'off')

and then call print().