[Rd] tcltk image reading problem (on a mac?): [tcl] encountered an unsupported criticial chunk type "eXIf"

[Prof Brian Ripley]

On 12/06/2020 03:49, Fox, John wrote:
> Dear Simon,
> 
>> On Jun 11, 2020, at 9:00 PM, Simon Urbanek <simon.urbanek using r-project.org> wrote:
>>
>> Wayne,
>>
>> that one is unrelated, but interesting - you can fix it with
>>
>> sudo install_name_tool -change \
>>   /usr/local/lib:/opt/X11/lib/libtk8.6.dylib \
>>   /usr/local/lib/libtk8.6.dylib \
>>   /usr/local/bin/wish8.6
>>
>> There is a bug in tcltk with IDs on the libraries which I have worked-around for R, but not for wish.
>>
>> Back to the original question - do you have any example of a file that doesn't work so I could test? Exif chunks are fairly rare in PNG and are a more late extension so I couldn't find any examples.
> 
> The code in Wayne's original message (copied below) generated the offending file:
> 
> library(tcltk)
> 
> fname <- "Rplot.png"
> png(filename = fname, width = 500, height = 500)
> hist(rnorm(20))
> dev.off()
> 
> tkimage.create("photo", file = fname)

There are several png() devices for R.  The default on macOS is to use 
Quartz, and that depends on macOS system functions so might well have 
changed with Mojave -> Catalina.

As a workaround, try e.g. png(type='cairo').  E.g.

fname <- file.path(tempdir(), "Rplot.png")
png(filename = fname, width = 500, height = 500, type="cairo")
hist(rnorm(20))
dev.off()

library(tcltk)
tkimage.create("photo", file = fname)

works for me on Catalina.


-- 
Brian D. Ripley,                  ripley using stats.ox.ac.uk
Emeritus Professor of Applied Statistics, University of Oxford