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EP-4742646-A1 - METHOD AND SYSTEM FOR CONVERTING THE FORMAT OF A GRAPHIC ARTS FILE

EP4742646A1EP 4742646 A1EP4742646 A1EP 4742646A1EP-4742646-A1

Abstract

A method for converting files associated with a print job for a flexographic printing plate includes converting a set of one-bit input files associated with the print job and having a first image file resolution, a first screening, a first color gamut, or a combination thereof into a single PDF file having a vector format; and using the PDF file to create a series of one-bit output files that have a second image file resolution, a second screening, a second color gamut, or a combination thereof.

Inventors

  • SCHEELE, JOACHIM
  • Otto, Nils Peter

Assignees

  • Esko-Graphics Imaging GmbH

Dates

Publication Date
20260513
Application Date
20241112

Claims (15)

  1. A method for converting files associated with a print job for a flexographic printing plate, the method comprising: converting a set of one-bit input files associated with the print job and having a first image file resolution, a first screening, a first color gamut, or a combination thereof into a single PDF file having a vector format; and using the PDF file to create a series of one-bit output files that have a second image file resolution, a second screening, a second color gamut, or a combination thereof.
  2. The method according to claim 1, further comprising conversion of tone values of rasterised images in a monochrome input file based upon identified tone values of individual screening dots.
  3. The method of claim 2, including converting the input file into a matrix of data points, wherein a center of each individual screening dot represents a data point, identifying data points having identical tone values, identifying contiguous areas of data points having identical tone values, and describing each identified contiguous area in vector format.
  4. The method of claim 2, comprising searching for tonal values of the identified screening dots in a library of screening dots.
  5. The method according to claim 3, wherein the library of screening dots resides in a library of data files belonging to a Raster Image Processor (RIP).
  6. The method according to any one of the foregoing claims, wherein the identification of screening dots in the one-bit input files is performed using an image recognition algorithm.
  7. The method according to any one of claims 4-6, wherein the search for the tonal values of the identified screening dots in the library of screening dots is executed by a search engine platform.
  8. The method according to claim 7, wherein the search engine platform comprises an Artificial intelligence (AI) supported database search engine platform trained using the library of data files belonging to the RIP, and searched using a supercell dimension configured to define a screen capable of expressing all available tonal values.
  9. The method according to any one of the previous claims, wherein the identification of tone values of the one-bit input files is supported by reading information contained in a file header of the one-bit files.
  10. The method according to any of the previous claims, wherein the set of one-bit input files is in a LEN format or a TIFF format.
  11. The method according to any of the previous claims, further comprising treating basic shapes comprising solid print areas as clusters of 100% screening dots.
  12. The method according to any of the previous claims, wherein text characters identified in the one-bit input files are transferred as text characters into the PDF file.
  13. The method according to claim 12, wherein the text characters are provided with font information.
  14. The method according to any of the previous claims, wherein the one-bit output files are in a LEN format.
  15. The method according to any of the previous claims, wherein the first image file resolution is lower than the second image file resolution, the second screening is more elaborate than the first screening, or the second gamut is wider than the first gamut.

Description

FIELD OF THE INVENTION The present invention relates to printing, more specifically to flexographic printing, and methods, and systems for implementation of such methods, for converting files associated with a print job for a flexographic printing plate. BACKGROUND OF THE INVENTION In flexographic printing prepress technology, plate making companies have backups of old data files in a run-length encoded format, e.g., a so-called LEN format. LEN is a one-bit run-length encoded format that was specially developed for imagers, such as film imagers or, e.g., Cyrel® Digital Imagers. The LEN format usually corresponds to the imager's imaging resolution and determines the positions where an imaging beam is switched on or off. The LEN format was introduced by the predecessors of Esko in the 1980s and has become a common standard in flexographic prepress technology. Plate making companies often store LEN files they have imaged for a long time in case a replacement for a worn-out flexographic printing plate may be needed. In this case, it is desirable to have preferably precisely the same imaging information for the imager without RIPping the input file (i.e. processing the file with a Raster Image Processor (RIP)) again. The most reliable way for this is to use the same LEN file again all the time. For this reason, preferably the LEN files are stored in backup files rather than the PDF input files they were made from. Therefore, some plate making companies have huge data volume of stored LEN files. In some cases, TIFF-format files have been stored instead of LEN files. Both types of files are bitmap files that store a black or white information for each image pixel in a matrix and comprise only information for one printing colour respectively for one flexographic printing plate. However, with progress in flexographic printing technology, many old imagers have been replaced by newer ones that work with higher imaging resolutions. These new imagers are not capable of imaging the old LEN files that were RIPped with coarser (e.g., lower) imaging resolutions. In addition, older screens have been replaced by more elaborate screens. For example, in highlight tone areas the fade out is no longer established by decreasing the dot size down to zero. As photopolymer plates do not hold printing dots below a certain size, today fade out is often established by keeping a certain minimum dot size and switching from AM (amplitude modulated) screening to FM (frequency modulated) screening. This method is described in U.S. patent number 11,142,013 B2, for example. Accordingly, there is a need for a method that allows converting old LEN files that were RIPped for old imagers having a first lower image resolution into a second LEN file having a second higher image resolution that can be imaged by new imagers having higher imaging resolutions. SUMMARY OF THE INVENTION One aspect of the invention is to provide a method for converting a first LEN file having a first lower resolution into a PDF file as an intermediate step. PDF files need less storage space and can be sent more easily over the Internet to other production sites. As an input file for flexographic printing, PDF files comprise image information in a vector format which allows scaling of the file without any loss in image resolution. In addition, a PDF file can be viewed and processed independently from the platform hardware or software on many different devices. To adapt these old files, which one day may become a redo job, to an up-to-date workflow it would be beneficial to have a conversion software tool that converts multiple monochrome LEN or TIFF bitmap files belonging to the same print job into one multicolour, vector format, PDF file that can be used again as input file for a second RIPping process. Thus, it is desirable to provide a method for converting all image files belonging to one set of printing plates from their bitmap-format into one PDF file that stores image information on a vector format. The following presents a simplified summary of the invention in order to provide a basic understanding of some example aspects of the invention. This summary is not an extensive overview of the invention. Moreover, this summary is not intended to identify critical elements of the invention or to delineate the scope of the invention. The sole purpose of the summary is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later. One aspect of the invention relates to a method for converting files associated with a print job for a flexographic printing plate. The method comprises converting a set of one-bit input files associated with the print job and having a first image file resolution, a first screening, a first color gamut, or a combination thereof into a single PDF file having a vector format; and using the PDF file to create a series of one-bit output files that have a second image file resolution, a second scree