12 the sheet is displaced in a y direction perpendicularly to the x direction the line of nozzles 11 in the print head extends in the y direction it may alternatively be slightly inclined relative to this direction an image is reproduced by scanning successive strips b of width l by moving the head 10 along the x direction main scan during a scan pass ink ejection is controlled to reproduce the desired image in the form of ink dots after each pass the number of rows of points is equal to the number of nozzles 11 and definition in the y direction is determined by the pitch p of the nozzles after each pass the sheet 12 is advanced in the u2212 y direction secondary scan and the print head 10 is caused to perform a new scan pass the displacements of the print head 10 and of the sheet 12 and the ejection of ink are all performed by means that are well known and which need not be described herein the input image data can be encoded in vector form in gray level raster form or in binary raster form the main characteristics of each of these forms of encoding are briefly explained below fig3 a is a graphical representation of an example of data in vector form the vectors are defined by the coordinates of their start and end points in an x y coordinate plane the vectors are written in a matrix of individual cells each having a specific address given by its x y coordinates the matrix being indexed relative to a print zone on the medium the values x and y are the incremental.