Digital halftoning with spiral dots
AssigneeAGFA Offset BV
InventorRudolf Bartels
Life of this patent
Estimating the term…
Abstract
A halftone raster image, suitable for rendering a continuous-tone image, which comprises a plurality of regularly tiled spiral dots. Said spiral dots comprise (i) image pixels arranged as a first arc (200) or as a plurality of arcs which together represent a first spiral (100), and (ii) non-image pixels arranged as a second arc (201) or as a plurality of arcs which together represent a second spiral (101), wherein neighbour halftone dots from said plurality of regularly tiled halftone dots represent a double spiral or triple spiral.
Claims20
A lithographic printing plate comprising 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 spiral defines ink accepting areas and the second spiral defines water accepting areas.
A flexographic printing plate comprising 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 spiral defines ink accepting areas.
A method of making a printing plate, the method comprising the steps of
- (i) making 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
- (ii) exposing said halftone raster image on a printing plate precursor.
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.
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 a single 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.
Dependencies are inferred from the claim text.