function correctBlendMode(blendMode, premultiplied) {
    return premultiplyBlendMode[premultiplied ? 1 : 0][blendMode];
}
changes blendMode according to texture format
@memberof PIXI.utils
@function correctBlendMode
@param {number} blendMode - supposed blend mode
@param {boolean} premultiplied - whether source is premultiplied
@returns {number} true blend mode for this texture