saved PDFs of rasters interpolate in some viewers

[davharris]

The code below creates a simple raster with 18 sharply-defined cells. If I ggsave it as a .png, I get a file that always renders correctly:

But if I save it as a .pdf, I get different behavior in different viewers. In Google Chrome, it renders like the .png. But in Apple Preview, it looks like this screenshot:

I get this behavior even if I explicitly set interpolate=FALSE in geom_raster, and regardless of the value I set for dpi, and various arguments to pdf like compress and onefile. I also get the same behavior if I "save as PDF" from the RStudio GUI.

I don't speak PDF/postscript, so I'm not sure how to diagnose this, but I'd be happy to provide additional information if for some reason this isn't reproducible on your machine.

Code

library(ggplot2)

data = data.frame(
  x = c(1L, 1L, 1L, 1L, 2L, 2L, 
        2L, 2L, 3L, 3L, 3L, 3L, 3L, 2L, 1L, 3L, 2L, 1L), 
  y = c(2L, 4L, 5L, 6L, 2L, 4L, 5L, 6L, 2L, 4L, 5L, 6L, 1L, 1L, 1L, 
        3L, 3L, 3L),
  fill = c(1, 0.85, 0.98, 0.92, 0.97, 0.88, 0.93, 0.88, 0.77, 0.9, 0.98, 
           0.87, 0.73, 0.5, 0.45, 0.48, 0.52, 0.8)
)

ggplot(data, aes(x = factor(x), y = factor(y), fill = fill)) +
  geom_raster()

ggsave("Rplot.pdf", ggplot(data, aes(x = factor(x), y = factor(y), fill = fill)) +
         geom_raster())

ggsave("Rplot.png", ggplot(data, aes(x = factor(x), y = factor(y), fill = fill)) +
         geom_raster())

SessionInfo:

R version 3.3.1 (2016-06-21)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
Running under: OS X 10.11.6 (El Capitan)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

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

other attached packages:
[1] ggplot2_2.1.0

loaded via a namespace (and not attached):
 [1] labeling_0.3     colorspace_1.2-6 scales_0.4.0     plyr_1.8.4      
 [5] rsconnect_0.4.3  tools_3.3.1      gtable_0.2.0     Rcpp_0.12.6     
 [9] grid_3.3.1       digest_0.6.10    munsell_0.4.3 

Files

https://cloud.githubusercontent.com/assets/843017/17610634/d981671a-600d-11e6-8211-b23fc216dda9.png

https://github.com/hadley/ggplot2/files/414529/Rplot.pdf

[davharris]

Sorry, looks like this is a duplicate of #417. If so, feel free to close it. Sorry for taking up your time!

[davharris]

On the other hand, if you think it would be useful, I'd be happy to write a PR that adds a line to ?geom_raster describing the issue and the geom_tile workaround so that nobody else wastes your time with this.

(sorry for the triple post!)

[hadley]

I corresponded with @pmur002 about this some time back - as far as we can tell the pdf is being written correctly (i.e. it contains a don't interpolate flag), and it's the viewer that's buggy.