Alpha blending and UIView background color

When I draw semitransparent textures with OpenGL, it looks like that I get them blended with EAGLView backgroundColor.

((EAGLView*)my_view).backgroundColor = [UIColor redColor];

opaque property is set to YES.

Now that image looks red, when I change to black it turns to gray(blended with black), to white it becomes white (even semitransparent black). What can it be?

my blending function setting is: src BFP_SRC_ALPHA, dest ONE_MINUS_SRC_ALPHA I tried also(possibly something like premultiplied alpha): src ONE dest GL_ONE_MINUS_SRC_ALPHA - it gives good result, but I get problems when drawing semitransparent quad(not texture).

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问题出现在预乘alpha使用src ONE dest GL_ONE_MINUS_SRC_ALPHA，并且args必须与预乘alpha也glColor4f（r * a，g * a，b * a，a）

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