28.1.9  Trimming image margins

Margins of an image, consisting of “empty” pixels with value 0 in all color channels, can be found and removed by using the trim command (see Section 5.2.5, Section 21.2.2 and Section 28.2.2 for other usages of trim).

• trim takes one mandatory argument and one or two optional arguments:
  • img, an image object.
  • Optionally, inv, the symbol.
  • Optionally, index, the symbol.
• trim(img ⟨,inv ⟩ ⟨,index ⟩) finds largest zero-pixel margins in img or its inversion if inv is given. If index is given, then the trimmed slice location (x,y) and dimensions (w,h) are returned as a sequence (x,y,w,h). Otherwise, a trimmed version of img is returned.
• To remove white margins, include the option inv when calling trim.

Example