I have a long Beamer presentation that gave me no errors or warnings on texlive 2013, but since I upgraded to texlive 2015, I get the following warning:

large interlaced PNG might cause out of memory (use non-interlaced PNG to fix this)

However, it does not indicate the line where this happens, making it a potentially arduous task to debug this... So how should I proceed here?

How can I identify the PNG causing trouble in a big Beamer presentation?

How can I make the PNG "non-interlaced"?

Many thanks!

  • never seen that, but the message is from pdftex not the macro package such as beamer or latex. isn't it given at the point the image is included? so you should see from the log which page you are on, you presumably can't have that many images on each page? – David Carlisle Aug 30 '16 at 9:09
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    tex always outputs [1], [2] etc as it ships out each page – David Carlisle Aug 30 '16 at 9:18
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    Well, it is a warning, not an error. Thus, the main question is if you are worried about if your PDF presentation will work on known or unknown computers. In the first case, just test the PDF. In the second, it is safer avoid any interlaced image (no just some image) to ensure that the PDF can be showed in computers with less memory. Use convert -interlace none to save your day. – Fran Aug 30 '16 at 9:42
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    Since the offending PNG cannot be spotter, I guess a one-liner to convert all the pngs in a folder to non-interlace mode keeping the same names would be a good answer for this question. – DaniCee Aug 30 '16 at 9:53
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    @DaniCee Look at the .log file, not the snippets texstudio is filtering out. In the complete logfile you will see the page marker [2] when beamer start a new page and you will see when an image is included. From this you should be able to narrow down the image which is causing this warning. – user36296 Aug 30 '16 at 11:00

converting Fran's comment into a CW answer

To avoid interlaced images, these can be converted by using

 convert -interlace none

For clarification:
If you want to convert a file called input_file.png to output_file.png, run the following command in your terminal (in the directory of input_file.png):

 convert -interlace none input_file.png output_file.png

The convert utility is part of the ImageMagick software package (https://imagemagick.org).

Now you can use output_file.png in your latex document without a warning.

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