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

[Ronggui Huang]

I see. So if I want to draw a rectangle by a function outside the
expose_fn, I need to refer to the drawable within the expose_fn. One
possibility is to use an environment, so I can refer to it
dynamically. Thanks,

Ronggui

2009/5/25 Michael Lawrence <mflawren at fhcrc.org>:
>
>
> On Sat, May 23, 2009 at 8:27 AM, Ronggui Huang <ronggui.huang at gmail.com>
> wrote:
>>
>> 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$GetRootWindow() would work, but it does not.
>
> You need to be drawing the rectangle within expose_fn, otherwise it won't
> show up. There should be no need to access the GdkWindow (da2) of the
> drawing area outside of expose_fn.
>
> Michael
>
>>
>> da <- gtkDrawingArea()
>> da2 <- NULL
>>
>> expose_fn <- function(widget,event,...){
>> img <- gdkPixbufNewFromFile("/media/wind/Pictures/kaehatu.jpg")$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
>
>



-- 
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