Re: [Rd] raster support in graphics devices

From: Romain Francois <romain.francois_at_dbmail.com>
Date: Fri, 04 Dec 2009 17:01:58 +0100

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/>

-- 
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
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