class_docstr: Class that provides a series of GL functions that do not fit
  in the object oriented part of gloo. An instance of this class is
  associated with each canvas.
docstr: Specify pixel arithmetic for RGB and alpha
  
  Parameters
  ----------
  srgb : str
      Source RGB factor.
  drgb : str
      Destination RGB factor.
  salpha : str | None
      Source alpha factor. If None, ``srgb`` is used.
  dalpha : str
      Destination alpha factor. If None, ``drgb`` is used.
docstr_tok: ["Specify","pixel","arithmetic","for","RGB","and","alpha","Parameters","--","--","--","--","--","srgb",":","str","Source","RGB","factor",".","drgb",":","str","Destination","RGB","factor",".","salpha",":","str","|","None","Source","alpha","factor",".","If","None",",","``","srgb","``","is","used",".","dalpha",":","str","Destination","alpha","factor",".","If","None",",","``","drgb","``","is","used","."]
code: def set_blend_func(
      self, srgb="one", drgb="zero", salpha=None, dalpha=None
  ):
      """Specify pixel arithmetic for RGB and alpha
  
      Parameters
      ----------
      srgb : str
          Source RGB factor.
      drgb : str
          Destination RGB factor.
      salpha : str | None
          Source alpha factor. If None, ``srgb`` is used.
      dalpha : str
          Destination alpha factor. If None, ``drgb`` is used.
      """
      salpha = srgb if salpha is None else salpha
      dalpha = drgb if dalpha is None else dalpha
      self.glir.command(
          "FUNC", "glBlendFuncSeparate", srgb, drgb, salpha, dalpha
      )
  
imports: import numpy
  from copy import deepcopy
  from .None import gl
  from ..color import Color
  from ..util import logger
label_desc: Use image node_id 11 for calling the BaseGlooFunctions obj's underlying member method code with example usage: obj.set_blend_func(srgb, drgb, salpha, dalpha) without return types