halftone vs monoprint

halftone

verb
  • To reproduce a photograph or other continuous tone image by the use of dots of various sizes. 

noun
  • A picture made by using the process of half-toning. 

  • An intermediate or middle tone in a painting, engraving, photograph, etc.; a middle tint, neither very dark nor very light. 

  • Synonym of semitone, half the interval between two notes on a scale. 

monoprint

verb
  • To print using this technique. 

noun
  • A form of printing on paper from a glass sheet to which oil paint has been applied; monotype. 

How often have the words halftone and monoprint occurred in a corpus of books? (source: Google Ngram Viewer )