Patent ID: 11915072
Assignee: AGFA OFFSET BV
Field: Audio-visual technology (Electrical engineering)
Classification: CPC G  B  H | IPC B  G  H

Claim 15:
16. A method of transforming a continuous-tone image to a halftone raster image for rendering a continuous-tone image, wherein said halftone raster image comprises a plurality of regularly tiled halftone dots wherein a distance between feed points (1003, 2003) between each neighboring halftone dots is from 50 μm to 400 μm,
wherein each of said halftone dots comprises:
(a) image pixels arranged as a first arc (200) or as a plurality of arcs which together represent a first spiral (100) and
(b) non-image pixels arranged as a second arc (201) or as a plurality of arcs which together represent a second spiral (101),
wherein the outer ends of the first spirals of neighbor halftone dots of said plurality of regularly tiled halftone dots are connected to represent a double spiral or triple spiral, and
wherein the first arc, the first spiral, the second arc, and the second spiral of each halftone dot each have a length and/or a thickness which is determined by local densities of the continuous-tone image,
the method comprising the step of transforming said continuous-tone image to said halftone raster image by means of at least one threshold tile, whereby
in highlights and midtones of the halftone raster image, the number of image pixels grows by increasing the length and/or the thickness of the first arc or the first spiral; and
in shadows of the halftone raster image, the number of image pixels grows by decreasing the length and/or thickness of the second arc or the second spiral.