code: public ColorImg clampAllChannelsToUnitRange(){
  		clampChannelToUnitRange(channel_r);
  		clampChannelToUnitRange(channel_g);
  		clampChannelToUnitRange(channel_b);
  		if(hasAlpha) clampChannelToUnitRange(channel_a);
  		return this;
  	}
docs: Clamps all values of all channels (including alpha if present) to unit range [0,1].
  Values less than 0 are set to zero, values greater than 1 are set to 1.
  @return this for chaining
  
  @see #clampChannelToUnitRange(int)