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paul mott
10-12-2012, 5:04 AM
This is something slightly different.

The image is formed by dots but not in the same way as the ‘dot-dithering’ process.

Each pixel, of the 8 bit original image, has a value between 0 and 255 and it is allocated a number of ‘dots’ which are then fed to the laser trigger at a speed of up to 12.5kHz. With a horizontal scan speed of 3000mm/min and step-over of 0.2mm most of these ‘dots’ overlap each other and thus produce the shades of grey seen in the image.

This is perhaps not a process that can be used with a proprietary laser machine but I just thought you may like to see the results.

Paul.

243029

Martin Boekers
10-12-2012, 11:03 AM
Is this similar to PhotGrav type system where it actually is a 1 bit file
with dots closer or farther apart and not uniform such as a halftone?

Lee DeRaud
10-12-2012, 12:19 PM
Is this similar to PhotGrav type system where it actually is a 1 bit file
with dots closer or farther apart and not uniform such as a halftone?You mean like a Jarvis or Stucki pattern? That still counts as "dithering", I think.

This sounds more like using very short horizontal variable-length line segments instead of dots, but I'm not sure I see the advantage.

Martin Boekers
10-12-2012, 1:40 PM
I guess I was mixing up dithering and halftoning.

I guess the one advantage would be if you were the one selling the software. :)

paul mott
10-13-2012, 3:30 AM
Hi Martin,

I think your understanding of the difference between Halftone and Dot Dithering is quite correct.

Give or take a bit…
With Halftone the dot spacing is equal but the size of individual dots varies whereas with Dot Dithering the dot size is constant but the dot positioning is mathematically calculated according to individual and adjoining pixel value. The mathematical formulas used being defined as ‘Stucki’,’Sierra’,’Floyd-Steinberg’ etc.

My example is only different in so far as it has a defined number of dots allocated for each pixel value and within each pixel the spacing of the allocated dots is equal (with a simple formula used to shift the relative dot position on each successive, horizontal, scan in order to prevent directional alignment causing moiré type patterning).

The software used was written by Art Fenerty back in 2007 and he generously made the C++ source code freely available so that others can customise it to suit their own requirements.

Paul.