Comments on: Plot markers transparency and color gradient

By: Yair Altman

Yair Altman — Tue, 31 May 2022 15:30:46 +0000

In reply to Dom. Dom - call drawnow *just before* you set hLine.MarkerHandle.FaceColorType to 'truecoloralpha'. Also, you made a typo in your code: it's truecoloralpha, not trucoloralpha.

By: Dom

Dom — Mon, 30 May 2022 16:49:16 +0000

In reply to Yair Altman. Yair I have tried your code with trucoloralpha and the markers do not appear transparent in R2021b, same as for Oliver.

By: Yair Altman

Yair Altman — Mon, 07 Mar 2022 18:47:48 +0000

In reply to Oliver. Oliver - you probably forgot to update hMarkers.FaceColorType to 'truecoloralpha':

x=1:10; y=10*x;
figure; hLine = plot(x,y,'o-');
hLine.MarkerFaceColor = 'r'; drawnow
hLine.MarkerHandle.FaceColorType = 'truecoloralpha';  % default='truecolor' without alpha
hLine.MarkerHandle.FaceColorData = uint8(255*[1;0;0;.3]);
drawnow

By: Oliver

Oliver — Mon, 07 Mar 2022 18:33:58 +0000

This seems to have been disabled in the most recent version of Matlab (R2021b). When I use this method the hMarker.FaceColorData does change, but the markers are not made transparent. Any ideas?

By: Yair Altman

Yair Altman — Wed, 26 Aug 2020 09:27:32 +0000

In reply to Pierre. @Pierre - thanks for sharing this clever useful trick

By: Pierre

Pierre — Wed, 26 Aug 2020 09:15:04 +0000

Hello, This post has been really useful to me. I just want to share a small trick. I have no idea whether it is reproducible or how it works, but it does the job for me (Win 10, R2019b). When I use plot function, the transparency settings are always reset by any command related to the current figure. However, when I use errorbar the transparency settings are kept. So, I have been using errorbar instead of plot, with a 'fake' error vector, and a capsize equal to 0. E.g.:

fake_y_error = zeros(length(data_y),1);
he = errorbar(x_data, y_data, fake_y_error)
drawnow
he_mh = he.MarkerHandle;
he_mh.FaceColorType = 'truecoloralpha';
he_mh.FaceColorData = uint8(255*[1;0;0;0.3]); 
he.CapSize = 0;

And, all the more convenient, it works when actual error-bars are needed.

By: Tim

Tim — Fri, 20 Dec 2019 22:56:45 +0000

Thank you for this post, it is very useful. It seems that when using plot3, if I have more than 25,000 points and I change my figure size or rotate the image, the MarkerHandle values revert back to the original settings and all color-information and/or transparency information is immediately reset. It is simple enough to reset the MarkerHandle properties following a viewpoint transformation but it is a bit of a pain, especially since I would like to explore the 3D point cloud using zoom and rotation. Have you discovered a similar issue and is there a workaround to this problem? The Matlab version I’m using is R2019a

By: Hassan

Hassan — Sun, 14 Jul 2019 15:44:01 +0000

In reply to Hassan. solved. the scatter plot was prepared for part of the full cell number!

By: Hassan

Hassan — Sun, 14 Jul 2019 12:19:38 +0000

Dear Yair, I have the following code that worked for me in the past. I have nothing new except or using different dataset (the Matlab version is the same 2016a). But it is not working now! I am getting a warning message after running the following command

hMarkers.FaceColorData=CMdata;
Warning: Error creating or updating Marker
 Error in value of property  ColorData
 Array contains incorrect data values

Here are the full code lines that I used:

CMtrans=uint8(255*(sum(hint.mat_norm(markersIn,:),1)./max(sum(hint.mat_norm(markersIn,:),1))));
CMdata=uint8([repmat(mCol'*255,1,length(CMtrans)); CMtrans]);
L2=scatter(ax,hint.xy(cellsIn,1),hint.xy(cellsIn,2),floor(ms2*frac),mCol,'filled');
drawnow;
hMarkers = L2.MarkerHandle;
hMarkers.FaceColorType = 'truecoloralpha';
hMarkers.FaceColorData=CMdata;
set(hMarkers,'FaceColorBinding','interpolated', 'FaceColorData',CMdata);

Any advice? Thanks, HM

By: Yair Altman

Yair Altman — Sun, 16 Jun 2019 15:09:42 +0000

In reply to Wolfgang. The extra pause() (or drawnow) call forces Matlab's graphic engine to flush (execute) any pending graphic rendering events in its graphics queue, thereby ensuring that when you set the transparency it "sticks". Without the pause/drawnow, the graphics queue might reset the transparency after you have set it, depending on internal timings over which we have no control. Related: http://undocumentedmatlab.com/blog/solving-a-matlab-hang-problem