Bug 340 - glClearColor with alpha set to 0 + glRTeadPixels = fail
Summary: glClearColor with alpha set to 0 + glRTeadPixels = fail
Alias: None
Product: Jogl
Classification: JogAmp
Component: core (show other bugs)
Version: 1
Hardware: All windows
: P3 normal
Assignee: Sven Gothel
Depends on:
Reported: 2008-01-31 02:00 CET by Sven Gothel
Modified: 2010-03-24 07:51 CET (History)
0 users

See Also:
SCM Refs:
Workaround: ---


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Description Sven Gothel 2010-03-24 07:51:09 CET

---- Reported by personwholives 2008-01-31 14:00:10 ----

I have an app where I am trying to render an image to a pbuffer, then save that
image to file.  I call gl.glClearColor(0, 0, 0, 0) to make a black, transparent
background.  After this, I render a few shapes and try to read the rendered
image back with gl.glReadPixels(0, 0, w, h, GL.GL_RGBA, GL.GL_UNSIGNED_BYTE, b).
 However, the read back result suffers from a complete lack of transparency. 
Even those places which I would expect to be transparent because nothing was
drawn there.  Every pixel in the populated data buffer has an alpha of 0xFF. 
This does not seem like correct behavior.

My system is a newer workstation class machine with an nVidia Quadro FX graphics
card, running windows XP.  Test done with JSR 231 1.1.0 on java 1.6 JDK, run
from within eclipse.  If any of that info is helpful.

---- Additional Comments From personwholives 2008-02-01 07:44:46 ----

Ok, I'm stupid.  Please ignore/close this issue.  One of these days I'll check
everything before leaping to the "it must be broken" conclusion.

---- Additional Comments From kbr 2008-02-01 09:50:06 ----

Closed as per submitter's comments.

--- Bug imported by sgothel@jausoft.com 2010-03-24 07:51 EDT  ---

This bug was previously known as _bug_ 340 at https://jogl.dev.java.net/bugs/show_bug.cgi?id=340