All,
Thank you in advance. My application needs to capture an image (that part
works), turn parts of it transparent (that part doesn’t), and redisplay the
image. I have the capture working, and, with a workaround, I have the
transparency working. The problem is that the workaround involves writing the
image to a file, and reading it back. Surely there is a better way than that.
I’m sure that I’m missing something, probably something simple…
Here’s the main snippet:
Code:
// I read in the bitmap, without transparency.
ref_ptr<Image> image = osgDB::readImageFile( "Ball.bmp");
// As expected, we do not see transparency.
{
ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer();
viewer ->setSceneData( makeGeode( image).get());
viewer->run();
}
// I convert the image to an RGBA format, if necessary, and set the
alpha (black is transparent).
My_OSG_Library::ConvertImageColorToAlphaValue( image);
// But, the image is still opaque!
{
ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer();
viewer ->setSceneData( makeGeode( image).get());
viewer->run();
}
// I check the image by writing it out to an .rgba file...
osgDB::writeImageFile( * image, "Ball.rgba");
// Since it checks, I read it back in...
image = osgDB::readImageFile( "Ball.rgba");
// And, voila! The transparency works!
{
ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer();
viewer ->setSceneData( makeGeode( image).get());
viewer->run();
}
My function, ConvertImageColorToAlphaValue, is apparently setting the alpha
values correctly. I’ve checked Ball.rgba, using gimp, and the black corners
are transparent, as expected. But, image doesn’t render transparently until I
read it back in.
So, my first question is: What needs to change in the image to “activate”
transparency?
My second question… If you look at my “helper” class, OSG_PixelComponent, which
I implemented to examine color values, and set the alpha values, does get the
job done… I suspect that there is a better way to do this, though, and I’m
wondering what that would be.
Thanks again,
Phil
Philip A. Tessier
------------------
Read this topic online here:
http://forum.openscenegraph.org/viewtopic.php?p=32421#32421
Attachments:
http://forum.openscenegraph.org//files/ball_142.bmp
http://forum.openscenegraph.org//files/osg_transparency_demo_405.cpp
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