Re: OVERLAYING IMAGES

["Mark Chan" <chanm(at)cadvision.com>]

Rick,

I have been avoiding object graphic so far.

I am interested in the real way, not the fake way.

Will you, or know where I can find some direct graphic example code of this
nature?

Thanks,
Mark Chan

"Rick Towler" <rtowler@u.washington.edu> wrote in message
AQlB6.8137$%o2.664880@news1.sttls1.wa.home.com">news:AQlB6.8137$%o2.664880@news1.sttls1.wa.home.com...
> If you literally want to control the opacity of your plots (vs. doing
> something with your data before contouring to fake it) you could try
> something like this:
>
>
> 1.plot your contour. This could be done in object graphics, or direct.
>
>
> 2.draw the plot to a buffer, read the buffer and you'll get an image
object.
> If you plotted with direct graphics you'll read the device you plotted to
to
> get the image data, then create an image object with that data.
>
>
> 3.add a 4th (alpha) channel to the image object like so:
>
>         image -> GetProperty, data = imagedata
>         imagedims = size(imagedata)
>         newimage=make_array(imagedims[1]+1,imagedims[2],imagedims[3], $
>                     /byte, /nozero)
>         newimage[0:2,*,*] = imagedata
>         newimage[3,*,*] = 255 (see note below)
>         image -> SetProperty, data = newimage
>
>   the value you set the alpha channel to will determine the opacity.  Your
> range is 0 (completely translucent) to 255 (opaque).
>
>
> 4.repeat 1-3 for the second plot.
>
>
> 5.create two idlgrpolygon objects, one on top of the other, and texture
map
> your images on them.
>
>
> 6.by changing the alpha value of your image objects you can fade them in
and
> out.
>
>
> If you are familiar with object graphics and have played around with the
> polygon object and have done some texturing then this is fairly easy.  If
> not, plan to spend some time with the documentation.  Everything is there,
> you'll just have to experiment a little.  Then encourage David to write
this
> Object Graphics book he has been threatening to write.  Speaking of David,
I
> think he has a program demonstrating this alpha channel stuff on his web
> site.  I would check that out.  It may even be a drop in solution.
>
> -Rick Towler
>
>
>
> "Mark Chan" <chanm@cadvision.com> wrote in message
> 9b38m8$f0f$1@news3.cadvision.com">news:9b38m8$f0f$1@news3.cadvision.com...
> > 1) plot some contour, using contour fill
> >
> > 2) oplot it with a different contour fill
> >
> > You get: only (2) appears (the other has been covered).
> >
> > Is there a way to make (2) translucent so that one can see both images
at
> > the same time?
> >
> > Thanks,
> > Mark
> >
> >
>
>