/**
* Sets the GL blending state according to the specified color mode. If <code>havePremultipliedColors</code> is
* true, this applies a blending function appropriate for colors premultiplied by the alpha component. Otherwise,
* this applies a blending function appropriate for non-premultiplied colors.
*
* @param gl the GL context.
* @param havePremultipliedColors true to configure blending for colors premultiplied by the alpha components, and
* false to configure blending for non-premultiplied colors.
*
* @throws ArgumentException if the GL is null.
*/
public static void applyBlending(GL2 gl, bool havePremultipliedColors)
{
if (gl == null)
{
String message = Logging.getMessage("nullValue.GLIsNull");
Logging.logger().severe(message);
throw new ArgumentException(message);
}
gl.glEnable(GL2.GL_ALPHA_TEST);
gl.glAlphaFunc(GL2.GL_GREATER, 0.0f);
if (havePremultipliedColors)
{
gl.glBlendFunc(GL.GL_ONE, GL.GL_ONE_MINUS_SRC_ALPHA);
}
else
{
// The separate blend function correctly handles regular (non-premultiplied) colors. We want
// Cd = Cs*As + Cf*(1-As)
// Ad = As + Af*(1-As)
// So we use GL_EXT_blend_func_separate to specify different blending factors for source color and source
// alpha.
bool haveExtBlendFuncSeparate = gl.isExtensionAvailable(GL_EXT_BLEND_FUNC_SEPARATE);
if (haveExtBlendFuncSeparate)
{
gl.glBlendFuncSeparate(
GL.GL_SRC_ALPHA, GL.GL_ONE_MINUS_SRC_ALPHA, // rgb blending factors
GL.GL_ONE, GL.GL_ONE_MINUS_SRC_ALPHA); // alpha blending factors
}
else
{
gl.glBlendFunc(GL.GL_SRC_ALPHA, GL.GL_ONE_MINUS_SRC_ALPHA);
}
}
}
