The PUTROW function writes the given array of bytes into the given lane number and row number. The comments about numbering and data type mentioned in GETROW also apply here. Note that in a newly created bigimage, it is invalid to (say) PUTROW lane 1 row 1, then PUTROW lane 1 row 3. That is, one can only either overwrite existing rows, or append the next row to the end of the lane. It is perfectly valid to write (say) lane 5 without lanes 1 to 4 existing.