Today I wanted to experiment with semi-transparent polygons (specifically triangles) in Matlab. What I need to do is to draw several (semi-transparent) polygons (which can overlap) into figure and then get matrix (of size H x W ) of RGB pixel values.
Example of what I have done so far:
H = 100; % Desired height (in pixels)
W = 150; % Desired width (in pixels)
f = figure('Position',[0,0,W,H],'Resize', 'off', 'DockControls', 'off','PaperUnits','inches','PaperPosition',[0,0,W,H]);
axis off;
hold on;
% Background
fill([0,W,W,0,0], [0,0,H,H,0], 'black', 'FaceAlpha',1, 'EdgeColor', 'none');
% Other polygons
fill([20,60,95], [40,80,10], 'r', 'FaceAlpha',0.5, 'EdgeColor', 'none');
fill([10,45,80], [10,90,25], 'g', 'FaceAlpha',0.5, 'EdgeColor', 'none');
% ... there will be more of them
set(gca,'Position',[0,0,1,1]) % This seems to be a problem
pixels = print('-RGBImage','-r1'); % Get RGB matrix
% Try to show the result
figure
imshow(pixels)
When the figure f is visible, I can see:
which is desired output. But as soon as I call print(...) and display the pixels, I see:
which has a white area on the right side, which is undesired.
I suppose, that problem is in calling of:
set(gca,'Position',[0,0,1,1])
but as I am not so experienced with Matlab, I don't know, how to fix it. Any ideas?
Note: Another approach could be directly using matrices. I found a function poly2mask, which could fill the triangles for me, but using that, I would need to compute all RGB(A) values of overlaying triangles myself. Furthermore poly2mask won't give 'fluent transitions' around the edges of triangles (as the output is boolean 0/1). Is there some function similar to poly2mask, but returning values in interval [0,1], which should give some smoothness on the edges?
P.S.: I am working on Ubuntu 14.04, using Matlab R2015b.
