Problem with 'Patch' graphics in 2014b - Splits in two along diagonal - MATLAB Answers - MATLAB Central

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Problem with 'Patch' graphics in 2014b - Splits in two along diagonal

Asked by David on 11 Nov 2014

Latest activity Answered by Joel on 22 Mar 2019

Accepted Answer by Mike Garrity

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I'm using 'Patch' to replace the boxes in box plots to change the colour etc. Code is:

h = findobj(gca,'Tag','Box');
for x=1:length(h)
   boxShade=patch(get(h(x),'XData'),get(h(x),'YData'), colours(x,:), 'linestyle', 'none');
   uistack(boxShade,'bottom');
end
delete(h);

This worked fine until I updated to 2014b where now the Patches appear to split in two along the diagonal, with the median in front of one half and behind the other. Example cut from exported pdf:

I am using the painters renderer as I'm outputting vector pdfs. Any ideas? I've seen some other talk that it's a bug from intersecting lines in a patch but there are no intersections here I believe as it's just a simple rectangle?

Any help greatly appreciated! David

1 Comment

Rainer on 6 Dec 2017

Experiencing the exactly the same problem with MATLAB R2015b. Any suugestions?

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23 Answers

Answer by Mike Garrity on 12 Nov 2014

Accepted Answer

The warning about DrawMode is trying to point you at the issue I described here:

http://blogs.mathworks.com/graphics/2014/11/04/sortmethod/

I'm not sure why you're getting that message when you call the axes function. Is it possible that you have something in your startup like this?

set(0,'DefaultAxesDrawMode','normal')

If you read that blog post, you'll see that choosing the wrong value for SortMethod can result in artifacts that are similar to what you're seeing, so it would probably be a good idea to track down where that warning is coming from.

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Ryan Webb on 9 Sep 2015

Has there been any progress on this? It is absolutely insane that you have broken the ability to export patch objects to .eps and .pdf, without providing a fix...

Jaime Palter on 24 Nov 2015

It's November 24, 2015, I'm using R2015a, and the problem of the broken polygons and HUGE file size for vector graphics (e.g. eps with -painters renderer) seems unfixed. Has there been any progress on this front? For my purposes, the increased file size is a deal-breaker when trying to produce publication-quality graphics with (e.g.) multiple panels with different colorbars.

Jonathan Lauderdale on 16 Mar 2016

This remains a big problem - just updated from 2014a to 2016a and the vector graphics look terrible! "contourf" plots are no longer nice patch objects, or even patches broken into a small number of smaller objects, but many many abutting rectangles in a brickwork pattern with the dreaded antialiased white borders (see screenshots below, same code, same antialias options in preview, or the attached pdfs). I have come across this before using other visualization and analysis software and in my experience, "downstream tools" like Inkscape have a much harder time handling the vastly increased number of simple objects, than a small number of complex objects. Please, please provide an option to produce single patches in vector output!

2016a:

2014a:

PS - one thing that is fixed is the colorbar now looks the same in the figure window and the output, although they are still embedded raster objects and, bizarrely, the 2016a version also has a dividing white border that runs from bottom left to top right!

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Answer by Steve Hansen on 13 Feb 2016

PennyCompare.pdf

Just checked R2015b an this significant problem remains.

For me and my research, you guys have broken one of the best parts about Matlab, quality vectorized figures. What is the point of having vectorized graphics if you are just going to chop up polygons into a large number of tessellated triangles?

I use contourf regularly to produce publication quality figures and the new graphics engine has made Matlab completely unusable for this purpose. Thus, this 'upgrade' represents a large step backwards for me.

My suggestion to anyone who needs a 'workaround' is to downgrade to Matlab R2014a until they fix this issue.

Here is a simple illustration of the problem:

load('penny.mat')
figure
contourf(P) 
colorbar
colormap copper
set(gca,'Ydir','reverse')
print(gcf,'penny.pdf','-dpdf')

I have attached the results from R2014a, R2015b and R2015b using the 'opengl' print option.

The individual pdf files sizes are, R2014a : 23 KB, R2015b : 245 KB, R2015b openGL : 77 KB

The R2015b version is an order of magnitude larger in file size due to the tessellation and looks terrible. The R2015b openGL version is better but is a raster image which defeats the utility of vectorized graphics. Only the R2014a result is usable.

3 Comments

Preetish Kakkar on 6 Apr 2018

I think this has been fixed in 17b, can you please check and confirm?

Mohsin Shah on 17 Jul 2018

I still have this problem with 2016a. Attached is an image taken from my research article. I wonder how to solve this issue.

Preetish Kakkar on 24 Jul 2018

Can you provide sample matlab code that was used to produce this image?

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Answer by Chris Churchill on 16 Mar 2016

Claiming that this is a bug with pdf viewers is really passing the buck. If I am creating vector art of a patch that is all the same color and one continuous area (even a perfect square!), I expect the same thing to be drawn in the vector output. Splitting into triangles not only breaks anti-aliasing, but it makes it impossible to edit in post-processing, which is why we use vector art in the first place. This bug is costing me many hours of grief in creating figures for publication. I can technically fix this in Illustrator by selecting all the patch triangles that should be one, and then merging them, but that doesn't work when there are thousands of triangles.

Mathworks should really automate this "merge" function by merging all polygons with the same color- that will be at least a step in the right direction on this problem.

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Answer by Tami Lieberman on 1 Jun 2016

I am having the same issue in MATLAB 2016a, that doesn't show up when I run the same scripts in 2013a. This is unacceptable.

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Answer by Jody Klymak on 7 Jul 2016

I truly feel mathwork has made the wrong decision here, and it is losing them customers. If a polygon is so complicated that it cannot be rendered well by a pdf viewer, then the user should have the option to rasterize the part of the figure that is too complicated, and should save it as an embedded image in the pdf. This is what python's matplotlib does. The PDFs produced by matplotlib combine raster objects and vector objects. As others have said, breaking up polygons defeats the purpose of rendering in polygons in the first place.

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Answer by Simon on 16 Aug 2016

Breaking up complex polygons into triangles is not just a EPS or PDF viewer antialiasing problem. It also results in 6x larger file sizes where filling constitutes most of the expense, e.g. area plots like Gunnar's. For scientific or engineering data, this can increase the file size from manageable to unmanageable.

I'm dissatisfied with my workaround of having to join the ends of lines into patch/area polygons with Illustrator.

Jody Klymak wisely suggests MATLAB rasterize complex parts of the figure. In this case it could just be the filling that's rasterized.

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Answer by fromLondon on 22 Aug 2016

+1 This is unacceptable. Virtually every Matlab user I know has a routine of exporting figures and then polishing them in Illustrator. Thanks to every area being dozens or hundreds of triangles now, this becomes an absolute chore. Please fix this!

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Answer by Doug Hull on 11 Nov 2014

The file we are creating in MATLAB is correct and what you are seeing is a bug in Adobe Reader, refer to Stataâ€™s description of the issue: http://www.stata.com/support/faqs/graphics/line-artifacts-in-filled-contour-plot/

The edges of the triangles are visible because the program used to display the file, such as Ghostview, is attempting to "smooth" the edges of the triangles where they meet.

An easy way to see this is to print the same figure to a PDF file and then open it in Acrobat Reader. The default preference setting is for Reader to "smooth line art". If you uncheck this option the figure looks fine.

To change the option in Acrobat Reader go to Edit->Preferences, select the Page Display category; you'll find it in the Rendering section

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Gunnar on 21 Apr 2015

Are there any plans to fix this problem in a future version? I can't expect colleagues to turn off their graphics smoothing for my figures. This is how a patch looks like when printed to pdf.

Mr T on 8 Jun 2015

Does anyone have a viable workaround aside from opening in 2014a? I'm having issues with patchy patches too.

Benedetto Barone on 23 Sep 2015

Hi again, has there been any change in Matlab 2015b regarding this problem?

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Answer by Dene Farrell on 20 Dec 2016

Edited by Dene Farrell on 20 Dec 2016

[a workaround: fix_matlab_vector_graphics]

I think that this issue has gotten confused because there are three distinctly different yet conflated issues with the vector graphics from Matlab.

Objects that should be single objects are fractured into many smaller objects.
Extraneous Cropping Paths are sometimes added to non-vector and/or vector objects.
Various anti-aliasing behaviors in different document viewers behave differently, which is beyond Mathwork's domain of what they can address, but they certainly can fix the first two problems.

I think it would be a start if they would at least acknowledge that 1 and 2 are real problems that arise from their own product, and they have nothing to do with adobe as you can see them in other viewers like Inkscape and Preview, in fact no viewer exists that does not make this output look weird by default.

Even if these vector graphics files looked nice in some given viewer, they are still a nightmare to edit due to all the fragmentation of the objects.

In the meantime...

Here is a hack fix that uses Illustrator programmatically to fix Matlab's output by uniting fractured paths of the same color. I don't think there is anyway to fully deal with this problem from outside of Mathworks core code.

fix_matlab_vector_graphics

Essentially it does the same thing that a previously posted fix ( fix_matlab_eps ) does, except it works with Illustrator instead of Inkscape. And for me the Illustrator fix works better, the objects are grouped together properly after it finishes running.

1 Comment

Nathan GREINER on 14 Oct 2018

Your fix_matlab_pdfs__jsx_plus_ai package worked perfectly for me. I used it to merge the myriad of patches resulting from a `fill` command. Thank you very much !

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Answer by Rob Campbell on 28 Mar 2017

This issue has been present for a decade at least. Disappointing, it must be said.

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Rob Campbell on 29 Apr 2017

I notice now that the problem might have become worse. I recently ran some old code that produced plots which didn't exhibit these artifacts two or three years ago but it now does.

Jesse Knight on 2 Jan 2018

I have the same problem.

Preetish Kakkar on 24 Jul 2018

Hi Rob, can you provide us with examples that got worse? We would be more than happy to help you and provide solutions.

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Answer by Vedrana Dahl on 8 May 2017

I have found following helpful: https://github.com/Conclusio/matlab-epsclean

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Jan Pecka on 14 Jun 2017

Same here, works great. Both with print() and hgexport().

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Answer by Walter Roberson on 24 Nov 2017

I happened to notice the following bug report https://www.mathworks.com/support/bugreports/1174438 marked as fixed for R2017b

"Unexpected fine lines across graphics in PDF, PS, EPS and SVG files"

" If you save a figure with MATLAB graphics to a PDF, PS, EPS, or SVG file and then open the saved file in a viewer application (such as Adobe Reader, GSView, or a web browser), unexpected fine lines can appear across filled areas. Zooming into the graphics does not eliminate the lines.

These lines are a side effect of anti-aliasing algorithms used by some viewer applications when displaying the shapes that MATLAB graphics creates in the files. The lines do not appear if you print the file to a paper copy because printers do not use anti-aliasing. "

" The current fix removes white lines that appear across any 2-D polygon object or geometry that is a single color. It is possible that the white lines still appear across other objects, such as a 2-D polygonal with textures or color gradients."

Could some of the people who have been affected by this problem test to see if this resolved the issue for their use case?

2 Comments

Jast on 27 Nov 2017

It mostly fixed the problem in the contour plot (small fine lines remain),but some issues remain in a colorbar. See picture attached.

Preetish Kakkar on 6 Apr 2018

Hi Jast, I don't see any attached pics in your link, can you please share code that is still showing up whitelines?

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Answer by Saul on 22 Apr 2015

Patches being broken up and rendered as triangles (as described by Mike Garrity) wouldn't necessarily be a problem except that PDF viewer renderers (Acrobat, Mac Preview, etc) tend to produce an thin edge artifact between perfectly abutting triangles when in anti-aliased (smooth text and line art) mode (as described by Doug Hull). You can tell this is a PDF renderer artifact because the on-screen thickness of the edge artifact doesn't increase as you zoom into the PDF.

Turning off anti-aliasing isn't a practical solution since it is an end user setting, and it will make just about every other PDF look horrible.

The hacky solution is to add a tiny offset to your patch coordinates so there is a small bit of overlap between triangles. You can make it so small as to be imperceptible but it will eliminate the renderer artifact.

Ultimately this is a PDF renderer bug that Adobe and other PDF rendering engines should fix.

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MikaJ on 26 May 2015

I have a similar problem with eps output of the maps generated by geoshow in 2014b - polygons are split to triangles. This is not only an aesthetic issue - it makes postprocessing of the maps with something like Adobe Illustrator next to impossible. In geoshow call, DisplayType is set to polygon. I'd expect polygons to appear in vector output as they are defined in the shapefile, so as to be able to select them as objects in the postprocessing phase.

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Answer by Dhruv Balwada on 11 Sep 2015

I am having similar problems even on matlab 2015a.

Its not only the white lines but also the contour labels are not visible. If you play close attention you can see that there are contour labels but they are not visible. The problem is not resolved by removing the smoothing feature from PDF viewers.

Does anyone know a good workaround? Would be highly appreciated.

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Answer by Silja Heilmann on 16 Dec 2015

I am having a similar problem though not in the context of a complex polygon - I see white lines along the diagonal of some but not all images when saved as eps in Matlab 2015a and imported into illustrator (see screen shot from illustrator).

Mike Garrity writes: "Yes, contourf tends to create polygons which are too complex for many applications, so we can't just put the whole polygon into the PDF file. We need to split it up." - I get that - but how come a square image or a square colorbar gets split in to two triangles?

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Answer by Ilja Maljutenko on 13 Apr 2016

Edited by Walter Roberson on 9 May 2016

Following are figures made using two different versions of Matlab and Python of same peaks data.

To illustrate the differences the .eps files are decomposed element by element using Inkscape (same version).

Matlab R2012b:

Matlab R2015: (note lots of white on the figure and ticks under the patches)

Python matplotlib:

I hope that forwarding this issue to viewer software can now be excluded.

For those who urgently need to fix eps figures, i can recommend trying this python software (which relies on Inkscape ).

It simply takes what Matlab have produced in eps file and merges it into one.

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Bryan on 27 Feb 2018

Agreed. If matplotlib in python can do it properly for free, then shouldn't paying Matlab users have at least the same functionality?

Also, on a related note, as was mentioned upthread, we can't embed raster images into a PDF in Matlab, as can be done in matplotlib. So I end up saving the linework by itself as a PDF, and the raster stuff by itself as PNG, and then combining the two in Illustrator. Takes me about 30 minutes each time. Then my supervisor asks for the plots to be remade. Or I need to make a loop of 100 plots...

Come on guys, what are we paying for.

Preetish Kakkar on 6 Apr 2018

Hi Bryan, sorry you are having trouble with this. I think this is fixed in 17b, can you please share any cases (along with sample script) where its still reproducible?

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Answer by Matthew Arthington on 5 Oct 2016

In case this may be a suitable temporary workaround for anyone else using Windows: I implemented an automated solution for myself. I save a figure in my current Matlab instance (2016b) as a fig file, then call a deployed function, compiled in Matlab 2013b, to open the figure file, save it as a PDF and close it again. Whilst it takes a few seconds to complete, it does result in a good rendering of patch objects in the final PDF, and reduces the need for further manual intervention. The function code to be compiled by calling

mcc -mv loadFigureIn2013bAndSaveAsPDF

in 2013b was as follows:

function loadFigureIn2013bAndSaveAsPDF(figureFile, filenameToSavePDF)
%This function is designed to only run in Matlab 2013b
v=ver('matlab');
assert(strcmpi(v.Release(2:end-1),'R2013b'),'loadFigureIn2013bAndSaveAsPDF must be run in Matlab 2013b');
close all
open(figureFile);
hFig=gcf;
adjustpdfpage(hFig);
saveas(hFig,filenameToSavePDF,'pdf');
close all
clear
end

I call the file from my newer Matlab instance using:

directory='C:\installPathOfEXE\';
myFigFileName='myFigFile.fig';
myPDFFileName='myPDFFile.pdf';
s=system(['"' directory 'loadFigureIn2013bAndSaveAsPDF.exe" "' myFigFileName '" "' myPDFFileName '"']);

One final note, I had to copy a tbb.dll file from C:\Program Files\MATLAB\R2013b\bin\win64 into the directory where I keep the loadFigureIn2013bAndSaveAsPDF.exe file.

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Answer by Hiroki Watanabe on 28 Oct 2016

The problem still persists on the 2016b release. I really hope they will fix this on the next release.

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Preetish Kakkar on 6 Apr 2018

I think this has been fixed in 17b, Please confirm if you still see the problem in 17b along with sample script.

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Answer by Jan on 15 Nov 2016

See https://de.mathworks.com/matlabcentral/answers/15388-artifacts-in-figures-exported-as-pdf-from-matlab: When the renderer of e.g. Acrobat Reader creates these light lines, there is no chance to "fix" this in Matlab.

2 Comments

Bas-Jan Zandt on 18 Nov 2016

Yes, but rather than having to fix the problem in Inkscape, Illustrator, Adobe reader and Preview for me and all my colleagues, I'd prefer to have the option to use the rendering method of the older Matlab versions that did not give rise to this problem.

Walter Roberson on 18 Nov 2016

.. that did not give rise to the problem as obviously, but which triggered other problems more obviously.

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Answer by Peter on 13 Feb 2017

Edited by Peter on 13 Feb 2017

Has this issue been addressed for 2017a? I see it has acquired a ticket as of last year: https://www.mathworks.com/support/bugreports/1174438

I don't think the workaround listed is particularly effective because while it addresses the print problem, the major use case isn't addressed: I suspect most people are reading PDFs on their screens, particularly during the peer review and research processes. And this might be a case where the "right" way to do it isn't necessarily the "correct" one. Has Mathworks talked to Adobe about the render bug?

It would be nice to have control over the triangulation strategy during the PDF render (i.e. force it to treat a patch object as a single unit with no tessellation, consequences be damned!). If I'm doing further editing in Illustrator, for instance, I don't want to recombine all of those triangles.

I'm spitballing here, but perhaps Mathworks could add another field onto affected r2017+ graphics that allows the user to control this, like

h.ObjectRendering = {'auto','unified','split'}

where "auto" does some form of hit-test on the image to find if there are intersections and maybe a heuristic on its complexity and applies the fragmentation as-needed, "unified" spits out a single closed-path, and "split" uses the current approach of triangulating everything.

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Rob Campbell on 29 Apr 2017

Apparently a fix may be in the pipeline in 2017b.

Jesse Knight on 2 Jan 2018

Working with a trial version of R2017b I can confirm this is still a problem. Looking forward to migrating my research to python ...

Preetish Kakkar on 6 Apr 2018

Hi Jesse, can you provide an example or a sample script where you still see the problem? We do expect 2d plots such as contours to be fixed in 17b.

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Answer by Nino on 22 Feb 2017

Edited by Nino on 22 Feb 2017

I use Plot2Latex to export my figures as svg and then integrate it in Latex. Looking at the svg from the "saveas" function used in Plot2Latex, I found that the patch objects are written like

....bliblablub.... style="fill:rgb(53,48,147); stroke:none;

I solved the issue by replacing all the "none" to the corresponding rgb color by opening the svg directly in MATLAB and the replacing can be scripted. It solved the problem for me. I doubt that it is general, though.

(offtopic, one can also remove the annoying white background of exported svgs in a similar way.)

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Answer by GK15 on 8 Jan 2019

Hello All,

I am experinencing similar issue whiel trying to export figure on Microsoft word 2017. I have Matlab 2015b on my computer. I didnt run into this issue last year when I had office 2010.

Does anyone know what is a potential fix? How do I get rid of vertical white fine lines which is not part of my data?

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Answer by Joel on 22 Mar 2019

If everything else fails, Adobe Acrobat Pro in combination with Adobe Illustrator (for example) may help. Here is how.

In Adobe Acrobat Pro, open the pdf figure or the pdf document in which the figure to be fixed is embedded.
Select 'Content Editing', 'Edit Text and Images'
Select the chopped up image (left click and drag to select all the patches at once, or shift and left click on individual patches if appropriate)
Right click, select 'Edit Using' and look for Illustrator
In Illustrator, select all the patches, then right click and select 'Release Clipping Mask'. If instead you see 'Make Clipping Mask', then you might have grabbed something else besides patches, such as a label, a tick or an axis.
Select 'File', then 'Save'.
The figure in Adobe Acrobat Pro is now fixed, hopefully. Save it.
Breathe.

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