Processing repeated images and memory recovery by GC

I recommend that you try to start building this example sooner rather than later ... maybe include a link to it or paste it into your next request (email to maintainer? a last gasp post here?) to give whoever has that very narrow set of abilities an incentive to look at it. Not having such an example can make it easier to just skip your request as being too vague and time-consuming to investigate.

Note that sending your email in plain text (a setting in your email software) rather than the HTML that this was sent in will help avoid us receiving frustrating glitches in your sample code.

Google "cran reprex" and read the vignette for further help on making an example.

On September 4, 2025 3:01:08 PM PDT, Bert Gunter <bgunter.4567 at gmail.com> wrote:

As I understand it and you, this kind of specialized technical question is
usually not a good fit to this list about general issues in R programming,
though someone may respond here of course. Alternatively, you may find it
useful to post on one (or some?) of the R SIGS (Special Interest Groups)
listed at https://www.r-project.org/mail.html  to see if one of them might
be a better fit. (Though some listed there may be inactive). Note also that
some R packages dealing with image processing have their own dedicated
lists.

Happy hunting.

Cheers,
Bert

On Thu, Sep 4, 2025 at 2:17?PM Steve Rowley via R-help <r-help at r-project.org>
wrote:

I have a question about repeated image processing and recovering memory via
garbage collection.

A couple images are displayed simultaneously for analysis, using
split.screen().  I'm looping over a large collection of images, using
jpeg/readJPEG(), png/readPNG(), and caTools/read.gif() to load an image
into memory from a file.  Then I use erase.screen() to erase the previous
image, use plot() to set up a plotting area, and display the image with
rasterImage().  Then the user elects some processing, and we move on to the
next image(s).

I'm very carefully not holding references to any of the previous images.
GC is indeed happening, but memory quickly fills up.  It certainly *looks*
as though the image memory is not being released: printing out trace info
using mem_used()[[1]] says memory use increases with each image, by about
the image size.  Forcing periodic GC's, measuring memory used before and
after, shows that no memory is recovered.

Some questions:

(1) Is it known that processing images in this way will lead to allocating
memory that is not recovered by GC?

(2) Are there any tools you'd recommend to see exactly *what* is filling up
memory, just in case it's not previous images, but some other problem?

This is R 4.4.2 (for now).  Running MacOS on an ARM processor.
___________
Steve Rowley <sgr at alum.mit.edu> Zoom: 839 529 4589
<https://us04web.zoom.us/j/8395294589?pwd=dlQ4MUFHK1NFOCtoZFpUNFRtZ2lSQT09

It is very dark & after 2000.  If you continue, you are likely to be eaten
by a bleen.

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