Re: [Rd] raster support in graphics devices

From: Gabor Grothendieck <ggrothendieck_at_gmail.com>
Date: Fri, 04 Dec 2009 08:28:41 -0500

Currently I have an application that saves the current graphics image (that was created with classic graphics or grid graphics) to a file and then reads the file back in using readBin:

png("my.png")
plot(1:10)
dev.off()
raw.img <- readBin("my.png", "raw", size = 1, n = 100000000)

(I am doing this on Windows but would like to be able to do it on any platform.)

Does the new raster functionality give me any way to get the object raw.img without creating the intermediate file, my.png? If so what is the corresponding code?

On Mon, Nov 30, 2009 at 8:17 PM, Paul Murrell <p.murrell_at_auckland.ac.nz>wrote:

> Hi
>
> This is for developers of extension packages that provide extra *graphics
> devices* for R.
>
> In the *development* version of R, support has been added to the graphics
> engine for sending raster images (bitmaps) to a graphics device. This
> consists mainly of two new device functions: dev_Raster() and dev_Cap().
>
> The R_GE_version constant (in GraphicsEngine.h) has been bumped up to 6 as
> a marker of this change.
>
> This means that, at a minimum, all graphics devices should be updated to
> provide dummy implementations of these new functions that just say the
> feature is not yet implemented (see for example the PicTeX and XFig devices
> in the 'grDevices' package).
>
> A full implementation of dev_Raster() should be able to draw a raster image
> (provided as an array of 32-bit R colors) at any size, possibly (bilinear)
> interpolated (otherwise nearest-neighbour), at any orientation, and with a
> per-pixel alpha channel. Where these are not natively supported by a
> device, the graphics engine provides some routines for scaling and rotating
> raster images (see for example the X11 device). The dev_Cap() function
> should return a representation of a raster image captured from the current
> device. This will only make sense for some devices (see for example the
> Cairo device in the 'grDevices' package).
>
> A little more information and a couple of small examples are provided at
> http://developer.r-project.org/Raster/raster-RFC.html
>
> Paul
> --
> Dr Paul Murrell
> Department of Statistics
> The University of Auckland
> Private Bag 92019
> Auckland
> New Zealand
> 64 9 3737599 x85392
> paul_at_stat.auckland.ac.nz
> http://www.stat.auckland.ac.nz/~paul/<http://www.stat.auckland.ac.nz/%7Epaul/>
>
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>

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