glBlendFunc

I'm using opengl ES and have a texture "binarygrid" loaded as:

glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, 256, 256, 0, GL_ALPHA, GL_UNSIGNED_BYTE, binaryGrid);

Which should fill a texture of r,g,b,a with 0,0,0,a.

glBlendFunc(GL_ZERO,GL_DST_COLOR);

With the above setting, glBlendFunc is drawing 0,0,0,a as a,a,a,a which is exactly what I want. I'm wondering if this is a bug, or have I actually stumbled on a solution. - Valles at www.redadept.com