Re: [Rd] raster support in graphics devices

From: Tobias Verbeke <tobias.verbeke_at_gmail.com>
Date: Sat, 05 Dec 2009 19:06:06 +0100

Hi,

Gabor Grothendieck wrote:

> Its not just the time. Its also the nuisance of having to manage files that > I never needed in the first place.

I agree with Gabor that it is more than a 'nice to have'.

There are situations (when integrating R with other applications) you don't want to touch a disk and manage files afterwards (e.g. when one wants to pass a byte string).

A recent question on the topic can be found here:

http://tolstoy.newcastle.edu.au/R/e8/help/09/11/5902.html

Best,
Tobias

> On Fri, Dec 4, 2009 at 11:01 AM, Romain Francois <romain.francois_at_dbmail.com

>> wrote:
> 

>> On 12/04/2009 03:19 PM, Gabor Grothendieck wrote:
>>
>>> Thanks.
>>>
>>> I am looking for the data to be just as if I had read in the png file (or
>>> wmf file or whatever).
>>>
>> Hi,
>>
>> You are after the binary payload of the rendered graph as a png file. So
>> you are going to have to go through a png file.
>>
>> It would be nice to be able to render to a binary connection, like a
>> rawConnection, but it seems like an expensive "nice to have"
>>
>>
>> grid.cap seems to give a bitmap and then would
>>> require some sort of processing to get the png or wmf, etc. form. Also
>>> note
>>> that I need it for classic graphics and not just grid graphics.
>>>
>> grid.cap does not seem to care, baptiste code uses traditional graphics
>>
>>
>> What I have right now works just as I want it _except_ I have to create a
>>> file and then read it back in which seems a waste.
>>>
>> Can you measure the time it takes to do dev.off() and readBin ?
>>
>>
>> On Fri, Dec 4, 2009 at 9:06 AM, baptiste auguie<
>>> baptiste.auguie_at_googlemail.com> wrote:
>>>
>>> Hi,
>>>> You can use grid.cap,
>>>>
>>>> x11()
>>>> plot(1:10)
>>>> g = grid.cap()
>>>> dev.off()
>>>> str(g)
>>>> # chr [1:672, 1:671] "white" "white" "white" "white" "white" ...
>>>>
>>>> but as far as I understand in ?grid.cap and the underlying code there
>>>> is no "capGrob" equivalent that wouldn't require opening a new device
>>>> before capturing the output.
>>>>
>>>> I hope I'm mistaken.
>>>>
>>>> Best,
>>>>
>>>> baptiste
>>>>
>>>> 2009/12/4 Gabor Grothendieck<ggrothendieck_at_gmail.com>:
>>>>
>>>>> 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/>
>>>>>> <http://www.stat.auckland.ac.nz/%7Epaul/>
>>>>>>
>>>>> <http://www.stat.auckland.ac.nz/%7Epaul/>
>> --
>> Romain Francois
>> Professional R Enthusiast
>> +33(0) 6 28 91 30 30
>> http://romainfrancois.blog.free.fr
>> |- http://tr.im/Gq7i : ohloh
>> |- http://tr.im/FtUu : new package : highlight
>> `- http://tr.im/EAD5 : LondonR slides
>>
>>
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