legend for transparent patch object is opaque ?
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Hello,
I create a simple figure with 2 patch objects where one of the patch is opaque and the other one is transparent (with facealpha set to 0.1) :
figure
x = [0 1 1 0];
y = [0 0 1 1];
patch(x,y,'red')
x2 = [3 6 6 3];
y2 = [3 3 6 6];
patch(x2,y2,'green','facealpha',0.1)
legend('red opaque -> OK','green is opaque instead of transparent -> WHY ?')
The legend does not reflect the fact that the green patch is transparent. I really need my legend to show if the patch is transparent or opaque. Is there a work around ?
Thanks !
采纳的回答
Ameer Hamza
2018-6-23
The problem is actually caused by the Rendrer of the figure object. In R2018a opengl seems to make the legend entries transparent, but in prior versions, you need to switch to 'painters' renderer to get this behavior. For example, try the following
f = figure;
f.Renderer = 'painters';
x = [0 1 1 0];
y = [0 0 1 1];
patch(x,y,'red')
x2 = [3 6 6 3];
y2 = [3 3 6 6];
patch(x2,y2,'green','facealpha',0.1)
legend({'red opaque -> OK','green is opaque instead of transparent -> WHY ?'}, 'Box', 'off')
2 个评论
Walter Roberson
2018-6-23
Traditionally only opengl supported transparency, but R2014b added transparency for painters
Matilda
2018-6-25
更多回答（1 个）
Yun Guo
2018-6-22
It is not very clear if you want green patch to be transparent, legend to be transparent, or both.
'facealpha' does work as expected. See example below.
- I changed the green patch's size so it overlaps with red patch to show transpareny works.
- I also removed legend box, so legend looks transparent.
figure
x = [0 1 1 0];
y = [0 0 1 1];
patch(x,y,'red');
x2 = [0.5 2 2 0.5];
y2 = [0.5 0.5 2 2];
patch(x2,y2,'green','facealpha',0.3)
l = legend('red opaque -> OK','green is opaque instead of transparent -> WHY ?');
set(l, 'Box', 'off')
5 个评论
Matilda
2018-6-22
Hello Yun,
Thanks for your answer. I agree that the green patch is transparent (I designed it that way with 'facealpha') but my problem is that this "transparency" is not displayed by the legend. When I run the code above, I get the figure below. The arrow shows that while the patch is indeed transparent, the green area in the legend is not. Therefore if I want to plot patches with different levels of transparency, I am unable to legend them properly, they all look the same.
Let me know if you have any suggestion on how to fix this,
Thanks !
Matilda
Ameer Hamza
2018-6-22
@Matilda, have you run the line
set(l, 'Box', 'off')
this is the expected output
Matilda
2018-6-22
Hello,
Then it must be a bug because on my version of matlab I do not get the expected result ... You can clearly see below that, as opposed to your own plot, mine shows the legend opaque...
Matilda
Ameer Hamza
2018-6-22
I am trying on R2018a. Since you have R2017b, which I cannot try at the moment. But to correctly check the opacity move the legend over the red portion like this
Matilda
2018-6-22
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