[Rd] using rasterImage within image

Simon Urbanek simon.urbanek at r-project.org
Wed Feb 9 20:25:04 CET 2011


I have committed something analogous to R-devel (your rotation code was not unlike mine, I replicated the color handling from R internals to be consistent, I fixed the drawing limits and added a check for x/y conformance). Note that useRaster can only be used when x, y form a regular grid. Although I tried a lot of corner cases (requiring quite a few fixes), I'm sure I did not test all of them, so volunteers please give it a go and compare it with non-raster output.

The only thing I'm not quite happy about is the argument name: useRaster. Personally, I hate camel case in R (it has crept in more recently making it horribly inconsistent) so please feel free to suggest a better name ;).


On Feb 9, 2011, at 10:06 AM, Ben Bolker wrote:

> On 11-02-08 10:03 PM, Simon Urbanek wrote:
>> Ben,
>> did you actually look at the result of your function with useRaster=TRUE ? ;) [Hint: don't use an image that is symmetric]
>> Apart from that nice bug there are more issues as well, try
>> image(matrix(1:4,2),col=1:3)
>> The underlying issue is that as.raster() is not quite what you would hope. 
>> Unfortunately I'm not aware of an easy fix (that doesn't involve going
> back to RGB decomposition).
>> In general, I think it's a nice option, but I don't think you'll get away with only a few lines...
>> Cheers,
>> Simon
>> On Feb 8, 2011, at 8:49 PM, Ben Bolker wrote:
>>> Has anyone yet tried incorporating rasterImage into the base image()
>>> function?  It seems to make a *huge* difference, with
>>> a very small number of added/changed lines of code.  (Of course I have
>>> barely tested it at all.)
>>> Is there any reason this *shouldn't* go into the next release?
>>>> source("image.R")
>>>> z <- matrix(runif(1e6),nrow=1000)
>>>> image(z)
>>>> image(z,useRaster=TRUE)
>>> (Patch against SVN 54284 attached; people can contact me if it doesn't
>>> go through and they want it.)
>>> Ben Bolker
>>> <image_diff.txt>______________________________________________
>>> R-devel at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>  Trying again. Rotated counterclockwise within R (although this *could*
> be coded in C if speed were important?)
>  Some brute-force testing suggests it is *slightly* slower for small
> images (7 vs 8 seconds for 1000 reps) and still much faster (and
> produces much smaller images, which don't suffer from antialiasing junk
> in my PDF viewer) for large images.
> <image_diff.txt><imagetest.R><image.R>

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