How to fix the size of markers when drawing in Matlab? Make the marker larger with local magnification instead of being fixed and unchanged.

I want to use the markers in the picture to represent the drones in the formation. When the canvas shrinks, the size of the markers should decrease accordingly, and when the area is zoomed in, the markers should increase accordingly. But the actual situation is exactly the opposite.

For example, for the following programs, the markers in the left image should be smaller, and the markers in the right image should be larger.

Can you help me? Thank you very much.

%%%

x = [10 20 30 40];

y = [20 10 10 20];

plot(x,y,'g', 'linewidth', 2)

text(x, y, '✤', 'color', 'r', 'fontsize', 20, 'HorizontalAlignment', 'center', 'VerticalAlignment', 'middle');

Answer 1

[Voss]

Using image objects or patch objects instead of text objects will cause the "markers" to scale appropriately when you zoom in or out.

[Voss]

Here's an example using image objects (the image file was created by making patch objects and then using exportGraphics to save to a .png file):

x = [10 20 30 40];
y = [20 10 10 20];

Zoomed-out version:

figure
plot(x,y,'g', 'linewidth', 2)
axis equal

xlim([-140 170]) % zoomed-out

hold on
img = imread('small.png');
alph = ~all(img==255,3);
for ii = 1:numel(x)
    image(img,'XData',x(ii)+[-5 5],'YData',y(ii)+[-5 5],'AlphaData',alph)
end

Zoomed-in version:

figure
plot(x,y,'g', 'linewidth', 2)
axis equal

xlim([4 46]) % zoomed-in

hold on
img = imread('small.png');
alph = ~all(img==255,3);
for ii = 1:numel(x)
    image(img,'XData',x(ii)+[-5 5],'YData',y(ii)+[-5 5],'AlphaData',alph)
end

[屹林]

Thank you very much ! Your suggestion is very useful, and I have tried it according to your guidance and achieved good results.

[Voss]

You're welcome!

Answer 2

[Harsh]

Hi,

From what I can gather, you are working with a plot in MATLAB and are unable to change the size of the text ‘✤’ which you are using as a marker.

Using ‘Normalized’ units should resolve this issue. Here is an example on how you can implement it in your code:

x = [10 20 30 40]; 
y = [20 10 10 20]; 
plot(x,y,'g', 'linewidth', 2) 
text(x, y, '✤', 'FontUnits', 'Normalized', 'FontSize', 0.1, 'color', 'r', 'HorizontalAlignment', 'center', 'VerticalAlignment', 'middle'); 

I hope this helps, thanks!

[Voss]

Using FontUnits 'normalized' makes the text font size a fixed fraction of the axes plot box height. Thus the text will resize when the axes height changes, but not when the x- or y-limits change, which I think is the desired behavior.

[屹林]

Thank you very much for your reply. But directly solving my problem,