code: function( rgbEq, alphaEq ){
      this._dat[ 0|BLEND_EQ_C] = rgbEq;
      this._dat[ 0|BLEND_EQ_A ] = alphaEq;
      this._set |= BLEND_EQ_SET | BLEND_EQ_A_SET;
      return this;
    }
docs: /*
  enums
  FUNC_ADD
  FUNC_SUBTRACT
  FUNC_REVERSE_SUBTRACT