Improvement of the Quality of Digital Printing Using Conditional Halftoning Function
Abstract:Printed images usually suffer to halftone dot contacts and thus lose their tone details where that contact takes place. Dot contacts should be avoided by means of certain technical approaches as early as image processing stages. This paper begins with the mathematical analysis of the mechanism of dot contact regarding different dot shapes of round, square and diamond. Then experiments were carried out to verify theoretical results derived through outputting single-color chips (20 mm×20 mm) using HP indigo 3550 press with paralyzing its dot gain compensation function. Chips under research were designed with dot area percentages varying from 25% to 80%, and two levels of resolution (600 and 1200 dpi) were used respectively for each dot area percentage. The theoretical analysis showed that dot contacts happened in case of dot area percentage 78.5% for the round dots, 50% for the square dots, 35% (first contact) and 65% (second contact) for the diamond dots, respectively. Jumps in dot density were employed to determine whether the dot contact happened or not. It was observed that halftone dot contacts occurred at the dot area percentage 71% for the round dots, 47% for the square dots, 34% (first contact) and 62% (second contact) for the diamond dots, all lower than their corresponding theoretical values. A conditional halftoning function was designed on the basis of experimental results, which was programmed using the PostScript language. The averaged density difference tested at the 34% of dot area percentage was 0.026, 47% was 0.025, 62% was 0.034 and 71% was 0.041, where the normal halftoning technology was used. In contrast, the averaged density difference was reduced to 0.005 at the 34%, 0.012 at the 47%, 0.016 at the 62% and 0.019 at the 71%, in the case of using conditional halftoning function. These results indicate that the conditional halftoning function is useful for diminishing halftone dot contacts. This study provides a promising halftoning method to improve the quality of digital printing that is subject to the negative effect of halftone dot contacts.
Document Type: Research Article
Publication date: January 1, 2011
For more than 25 years, NIP has been the leading forum for discussion of advances and new directions in non-impact and digital printing technologies. A comprehensive, industry-wide conference, this meeting includes all aspects of the hardware, materials, software, images, and applications associated with digital printing systems, including drop-on-demand ink jet, wide format ink jet, desktop and continuous ink jet, toner-based electrophotographic printers, production digital printing systems, and thermal printing systems, as well as the engineering capability, optimization, and science involved in these fields.
Since 2005, NIP has been held in conjunction with the Digital Fabrication Conference.
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