readPNG gives warnings and doesn't execute sample code from help files
Joris,
On Feb 14, 2011, at 10:05 AM, Joris Meys wrote:
Dear all, I noticed in the latest R version (R.2.12.1) that the readPNG gives following warning when running the example code in the help file (or when using any other png for that matter) : 50: In rasterImage(img, 1.2, 1.27, 1.8, 1.73) : Per-pixel alpha not supported on this device No picture is shown, and code I used to be able to run, doesn't run any more.
You may want to use a device that supports alpha. The R logo in the example uses alpha so are probably the images you are using. If you don't want to (or can't) use a device that supports alpha, you'll have to flatten the alpha, - i.e. plot just img[,,1:3] However, most images don't have color where alpha is zero, so you'll have to replace it with the background color, e.g.: r = as.raster(img[,,1:3]) r[img[,,4] == 0] = "white" Cheers, Simon
sessionInfo()
R version 2.12.1 (2010-12-16) Platform: i386-pc-mingw32/i386 (32-bit) locale: [1] LC_COLLATE=English_United States.1252 LC_CTYPE=English_United States.1252 LC_MONETARY=English_United States.1252 [4] LC_NUMERIC=C LC_TIME=English_United States.1252 attached base packages: [1] grDevices datasets splines graphics stats tcltk utils methods base other attached packages: [1] png_0.1-2 svSocket_0.9-51 TinnR_1.0.3 R2HTML_2.2 Hmisc_3.8-3 survival_2.36-2 loaded via a namespace (and not attached): [1] cluster_1.13.2 grid_2.12.1 lattice_0.19-13 svMisc_0.9-61 tools_2.12.1 -- Joris Meys Statistical consultant Ghent University Faculty of Bioscience Engineering Department of Applied mathematics, biometrics and process control tel : +32 9 264 59 87 Joris.Meys at Ugent.be ------------------------------- Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php