On Oct 21, 2013, at 9:07 PM, Yihui Xie wrote: > Perhaps yes. Sorry I did not check the bug reports. Can someone > elaborate on the "undesirable artefacts"? I made two heatmaps using > png() and CairoPNG(), respectively. I can see the difference, but it > is not very clear to me what the artefacts are, or what the facts > should be. >
The Cairo package does "smart" anti-aliasing - it aligns lines that are perpendicular to the axes such that they centered at pixels. That avoids the anti-aliasing effects that Brian was talking about for the heatmap example. This enables Cairo to have full anti-aliasing support and still render heatmaps without artifacts. However, there is no way around the anti-aliasing artifacts if you use arbitrary polygons without borders. For example: library(deldir) plot(c(-1,1),c(-1,1),ty='n') for(p in tile.list(deldir(rnorm(200),rnorm(200)))) polygon(p$x,p$y,col=heat.colors(15)[runif(1,1,15)], border=NA) That said, in our experience the Cairo approach works very well in practice. Cheers, Simon > png(): http://i.imgur.com/lKrFG9i.png > CairoPNG(): http://i.imgur.com/Dv0rsKK.png > > f = function(dev, ...) { > dev(...) > x = y <- seq(-4*pi, 4*pi, len = 27) > r = sqrt(outer(x^2, y^2, "+")) > z = cos(r^2)*exp(-r/6) > image(z, main = deparse(substitute(dev))) > dev.off() > } > f(grDevices::png, 'png-base.png', type = 'cairo') > f(Cairo::CairoPNG, 'png-Cairo.png') > > Thanks! > > Regards, > Yihui > -- > Yihui Xie <xieyi...@gmail.com> > Web: http://yihui.name > Department of Statistics, Iowa State University > 2215 Snedecor Hall, Ames, IA > > > On Mon, Oct 21, 2013 at 5:28 PM, Paul Murrell <p...@stat.auckland.ac.nz> > wrote: >> Hi >> >> Is this the same as "Bug 15462" ? >> https://bugs.r-project.org/bugzilla3/show_bug.cgi?id=15462 >> >> Paul >> >> >> On 10/22/13 10:43, Yihui Xie wrote: >>> >>> Hi, >>> >>> It seems that anti-aliasing in png(type = 'cairo') is not well >>> supported for the point symbols without boarders, e.g. pch = 16. The >>> Cairo package works well, though. You can compare png() with >>> CairoPNG(): >>> >>> png(): http://i.imgur.com/8niB3jX.png >>> CairoPNG(): http://i.imgur.com/FZBJOxm.png >>> >>> f = function(dev, ..., main = '') { >>> dev(...) >>> plot(c(1, 2, 1, 2), c(1, 1, 2, 2), pch=c(16, 19), cex=c(2, 2, 15, 15), >>> xlim=c(0.5, 2.5), ylim=c(0.5, 3), main = deparse(substitute(dev))) >>> dev.off() >>> } >>> f(grDevices::png, 'png-base.png', type = 'cairo') >>> f(Cairo::CairoPNG, 'png-Cairo.png') >>> >>> If I remove the border for pch=19 (i.e. lwd=0), the point shows rough >>> edges as well. >>> >>> I'm not sure if that is expected, or it is due to my misconfiguration >>> somewhere. I installed R via `apt-get install r-base-dev` under Ubuntu >>> using the CRAN repository. >>> >>>> sessionInfo() >>> >>> R version 3.0.2 (2013-09-25) >>> Platform: x86_64-pc-linux-gnu (64-bit) >>> >>> locale: >>> [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C >>> LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8 >>> [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 >>> LC_PAPER=en_US.UTF-8 LC_NAME=C >>> [9] LC_ADDRESS=C LC_TELEPHONE=C >>> LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C >>> >>> attached base packages: >>> [1] stats graphics grDevices utils datasets methods base >>> >>> loaded via a namespace (and not attached): >>> [1] Cairo_1.5-2 tools_3.0.2 >>> >>>> capabilities() >>> >>> jpeg png tiff tcltk X11 aqua http/ftp sockets >>> TRUE TRUE TRUE TRUE TRUE FALSE TRUE TRUE >>> libxml fifo cledit iconv NLS profmem cairo >>> TRUE TRUE TRUE TRUE TRUE TRUE TRUE > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
