changing opacity/transparency of an image

[Paul Groot]

Erin,

Since EPrime doesn't have a builtin transparency option, this would be
something you will have to implement yourself. The most straightforward way
would be to manipulate an offscreen bitmap using the GetPixel/SetPixel
functions. However, using EBasic this way would take ages. Another option
would be to have an external DLL-function to do all the work (using
optimized C++ code for example), but unfortunately this requires serious
programming skills.

best,
paul

2012/8/7 Erin <erin.siebert at gmail.com>

> I am trying to build an experiment where I incrementally "black out" an
> image displayed on a black background.  I want to be able to set the image
> opacity from 0% to 100% in 2% increments.  I will keep the image opacity
> level constant within a session, but want to be able to change it easily
> between sessions.  I know I could achieve this in Photoshop by putting a
> black background behind my image, adjusting the image's opacity, and
> re-saving the image.  However, I want to be able to draw randomly from a
> very large bank of images for each stage of the experiment, and it would be
> prohibitively impractical to adjust all the images manually in Photoshop
> for each opacity level.
>
> I found a post in this forum on how to fade between two different colors
> (How to fade from slide1 to slide2 (inline?)), however I haven't been able
> to find any information on adjusting  opacity/transparency.  Any help would
> be very appreciated.  Thank you!
>
> Erin
>
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