webshot fails to take screenshots of local .html under Windows

[fdetsch]

I try to take screenshots of local .html files. The below code works fine on Ubuntu 16.04 64-bit, R version 3.0.0, but fails on the same machine using the same R version under Windows 10.

## sample widget
library(mapview)
m <- mapview(breweries91)

## save to html
htmlwidgets::saveWidget(widget = m@map, file = "~/map.html")

## save html to png 
webshot::webshot(url = "C:/Users/fdetsch/Documents/map.html", 
                 file = "C:/Users/fdetsch/Documents/map.png")

More precisely, the created .html looks just fine when opened e.g. in Firefox and the code does not throw any errors, but the resulting image is just black. On Ubuntu, by contrast, the created .png file looks just as expected. Here is my session info.

R version 3.3.0 (2016-05-03)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows >= 8 x64 (build 9200)

locale:
[1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252    LC_MONETARY=German_Germany.1252
[4] LC_NUMERIC=C                    LC_TIME=German_Germany.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] mapview_1.0.29     leaflet_1.0.1.9003

loaded via a namespace (and not attached):
 [1] Rcpp_0.12.5         raster_2.5-2        magrittr_1.5        gdalUtils_2.0.1.7   munsell_0.4.3      
 [6] colorspace_1.2-6    viridisLite_0.1.3   lattice_0.20-33     foreach_1.4.3       plyr_1.8.3         
[11] tools_3.3.0         webshot_0.3         rgdal_1.1-10        grid_3.3.0          R.oo_1.20.0        
[16] png_0.1-7           latticeExtra_0.6-28 htmltools_0.3.5     iterators_1.0.8     yaml_2.1.13        
[21] digest_0.6.9        RColorBrewer_1.1-2  htmlwidgets_0.6     R.utils_2.3.0       codetools_0.2-14   
[26] sp_1.2-3            scales_0.4.0        R.methodsS3_1.7.1   stats4_3.3.0        jsonlite_0.9.20    
[31] satellite_0.2.0 

[timelyportfolio]

see #10, I think you just need to append file:/// to make it a valid url.

[wch]

I suppose it would be helpful to include an example of the correct path to use on Windows. Or maybe it would be better to make webshot automatically fix paths on Windows.

[fdetsch]

file:/// works, thanks a lot! Winston, wouldn't it be possible to retrieve the required OS information via Sys.info()[["sysname"]] and add file:/// if necessary?

[wch]

@fdetsch We would also have to have a good way of detecting whether the path is to a local file, or a remote one. I think searching for the regex ^\w+?:// should work.

[yihui]

I'd recommend you to avoid absolute paths -- setwd() to the directory of the html file, take a screenshot using the base filename, and restore the working directory. Then you would not need to worry about issues like file:/// or forward slashes / backslashes.

[alipprc]

I have the opposite problem !!!
can somebody help me here :
https://stackoverflow.com/questions/50154257/webshot-fails-to-take-screenshots-of-local-html-under-linux

[gauravdhiman]

@timelyportfolio thanks for your pointer. I was struggling with it for last 2 hours ... you saved me many more hours !!