glBlendFunc(GL_ONE_MINUS_SRC_ALPHA, GL_SRC_ALPHA);
alpha is replaced by a black color.
i tried with
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
it works for alpha, but all pixels are transformed, like this : a green pixel from texture_1 is transformed into a light blue pixel when it’s over the blue pixel from texture_0.