[R] Draw a rectangle on top of an image using RGtk2?

[Ronggui Huang]

Thanks, Michael. Just one more follow-up question. Is there other way
to get the "GdkDrawable" (here da2) without using <<- or other
assignment operation from within expose_fn? I thought
da$GetRootWindow() would work, but it does not.

da <- gtkDrawingArea()
da2 <- NULL

expose_fn <- function(widget,event,...){
img <- gdkPixbufNewFromFile("/media/wind/Pictures/kaehatu.jpg")$retval
da2 <<-widget[["window"]]
gdkDrawPixbuf(da2, gc = NULL, pixbuf=img,
event[["area"]][["x"]], event[["area"]][["y"]],
event[["area"]][["x"]], event[["area"]][["y"]],
event[["area"]][["width"]], event[["area"]][["height"]])
 return(FALSE)
}
gSignalConnect(da,"expose-event",expose_fn)
w<-gtkWindow(show=F)
w$SetSizeRequest(400,300)
w$Add(da)
w$Show()

dgc <- gdkGCNew(da2)
gdkGCSetLineAttributes(dgc, line.width=2, line.style="solid","round","round")
gdkDrawRectangle(da2,dgc,FALSE,10,10,100,100)


Ronggui

2009/5/23 Michael Lawrence <mflawren at fhcrc.org>:
>
>
> On Fri, May 22, 2009 at 11:27 PM, Ronggui Huang <ronggui.huang at gmail.com>
> wrote:
>>
>> Dear all,
>>
>> I use gtkImageFromFile to display an image. Then I want to do some
>> gsignal to handle mouse event. I click the mouse and move a another
>> position and release. I can get the position of the firs click and the
>> release position,  then I would to draw a rectangle to display the
>> region I have selected. I need some hints on what functions should I
>> look for. I tried to google but don't know how.
>
> The GtkImage widget is just for showing images. If you want to start doing
> interactive graphics, I'd suggest moving to the more general GtkDrawingArea
> widget and connecting to the expose-event signal. You can then use GdkPixbuf
> for loading and drawing the image onto the drawing area. And then draw a
> rectangle on top with gdkDrawRectangle().
>
> See demos drawingArea and images.
>
> Michael
>
>>
>> Thanks.
>>
>> --
>> HUANG Ronggui, Wincent
>> PhD Candidate
>> Dept of Public and Social Administration
>> City University of Hong Kong
>> Home page: http://asrr.r-forge.r-project.org/rghuang.html
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
>



-- 
HUANG Ronggui, Wincent
PhD Candidate
Dept of Public and Social Administration
City University of Hong Kong
Home page: http://asrr.r-forge.r-project.org/rghuang.html