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CHANGES - OpenPrinting libcupsfilters v2.0b1 - 2022-11-14

CHANGES IN V2.0b1 (TBA)

  • Introduced the filter functions concept converting filter executables into library functions with common call scheme, moving their core functionality into libcupsfilters and allowing easier use by Printer Applications. Common data about the printer and the job are supplied via a data structure, which is the same for each filter in a chain of filters. The data structure can be extended via named extensions.

  • Converted nearly all filters to filter functions, only exceptions are rastertoescpx, rastertopclx, commandtoescpx, commandtopclx, and foomatic-rip. The latter is deeply involved with Foomatic PPDs and the others are legacy printer drivers. Filter functions which output PostScript are implemented in libppd.

  • Converted CUPS' rastertopwg filter into the cfFilterRasterToPWG() filter function.

  • Created new cfFilterPWGToRaster() filter function primarily to print raster input (PWG Raster, Apple Raster, images) to CUPS Raster drivers in driver-retro-fitting Printer Applications.

  • Converted all filter functions to completely work without PPD files, using only printer and job IPP attributes and an option list for options not mappable to IPP attributes. For some filter functions there are also wrappers for a more comprehensive PPD file support in libppd.

  • Added concept of callback functions for logging, for the filter functions not spitting their log to stderr.

  • Added concept of callback functions for telling that a job is cancelled so that filter functions can return early. This change is to get more flexibility and especially to support the papplJobIsCanceled() of PAPPL.

  • Added new streaming mode triggered by the boolean "filter-streaming-mode" option. In this mode a filter (function) is supposed to avoid everything which prevents the job data from streaming, as loading the whole job (or good part of it) into a temporary file or into memory, interpreting PDF, pre-checking input file type or zero-page jobs, ... This is mainly to be used by Printer Applications when they do raster printing in streaming mode, to run with lowest resources possible. Currently cfFilterGhostscript() and cfFilterPDFToPDF() got a streaming mode. In streaming mode PostScript (not PDF) is assumed as input and no zero-page-job check is done, and all QPDF processing (page management, page size adjustment, ...) is skipped and only JCL according to the PPD added.

  • Added raster-only PDF and PCLm output support to the ghostscript() filter function. Note that PCLm does not support back side orientation for duplex.

  • cfFilterPDFToPDF(): Introduced new "input-page-ranges" attribute (Issue #365, Pull request #444, #445).

  • Added cfFilterChain() filter function to run several filter functions in a chain.

  • Added filterPOpen() and filterPClose() functions which similar to popen() and pclose() create a file descriptor which either takes data to feed into a filter function or provides data coming out of a filter function.

  • Added new cfFilterExternal() filter function which calls an external CUPS filter (or backend) executable specified in the parameters, for example a legacy or proprietary printer driver which cannot be converted into a filter function. Backends can be run both for job execution or in their discovery mode. The environment in which the external executable is running is resembling CUPS as best as possible.

  • Added support for the back and side channels which CUPS uses for additional communication between the filters and the backend into the filter function infrastructure. Now filter functions can use these channels and also CUPS filters or backends called via the cfFilterExternal() function. Printer Applications can easily create the needed pipes via the new function cfFilterOpenBackAndSidePipes() and close them via cfFilterCloseBackAndSidePipes() and filter functions used as classic CUPS filters get the appropriate file descriptors supplied by ihe ppdFilterCUPSWrapper() function of libppd.

  • Added the cfFilterUniversal() filter function which allows a single CUPS filter executable which auto-creates chains of filter function calls to convert any input data format into any other output data format. So CUPS can call a single filter for any conversion, taking up less resources. Thanks to Pranshu Kharkwal for this excellent GSoC project (Pull request #421).

  • Added functions to read out IPP attributes from the job and check them against the IPP attributes (capabilities) of the printer: cfIPPAttrEnumValForPrinter(), cfIPPAttrIntValForPrinter(), cfIPPAttrResolutionForPrinter()

  • Added functions cfGenerateSizes() and cfGetPageDimensions() to match input page sizes with the page sizes available on the printer according to printer IPP attributes.

  • Moved IEEE1284-device-ID-related functions into the public API of libcupsfilters, also made the internal functions public and renamed them all to cfIEEE1284...(), moved test1284 to cupsfilters/.

  • Extended cfIEEE1284NormalizeMakeAndModel() to a universal function to clean up and normalize make/model strings (also device IDs) to get human-readable, machine-readable, or easily sortable make/model strings. Also allow supplying a regular expression to extract driver information when the input string is a PPD's *NickName.

  • When calling filters without having printer attributes, improved understanding of color mode options/attributes. Options "output-mode", "OutputMode", "print-color-mode", and choices "auto", "color", "auto-monochrome", "process-monochrome", and "bi-level" are supported now and default color mode is RGB 8-bit color and not 1-bit monochrome.

  • When parsing IPP attributes/options map the color spaces the same way as in the PPD generator (Issue #326, Pull request #327).

  • Added new oneBitToGrayLine() API function which converts a line of 1-bit monochrome pixels into 8-bit grayscale format (cupsfilters/bitmap.[ch]).

  • Removed support for asymmetric image resolutions ("ppi=XXXxYYY") in cfFilterImageToPDF() and cfFilterImageToRaster() as CUPS does not support this (Issue #347, Pull request #361, OpenPrinting CUPS issue #115).

  • Removed now obsolete apply_filters() API function to call a chain of external CUPS filter executables, as we have filter functions now and even can call one or another filter executable (or even backend) via cfFilterExternal().

  • Build system, README: Require CUPS 2.2.2+ and QPDF 10.3.2+. Removed now unneeded ./configure switches for PCLm support in QPDF and for use of the urftopdf filter for old CUPS versions.

  • Renamed function/data type/constant names to get a consistent API: Functions start with "cf" and the name is in camel-case, data types start with "cf_" and are all-lowercase with "" separators, constants start with "CF" and are all-uppercase, also with "_" separators.

  • Bumped soname to 2, as we have a new API now.

  • Build system: Remove '-D_PPD_DEPRECATED=""' from the compiling command lines of the source files which use libcups. The flag is not supported any more for longer times already and all the PPD-related functions deprecated by CUPS have moved into libppd now.

  • Older versions of libcups (< 2.3.1) had the enum name for fold-accordion finishings mistyped. Added a workaround.

  • Added support for Sharp-proprietary "ARDuplex" PPD option name for double-sided printing.

  • Build system: Add files in gitignore that are generated by "autogen.sh", "configure", and "make" (Pull request #336).

  • Fixed possible crash bug in oneBitLine() function.

  • In ghostscript() pass on LD_LIBRARY_PATH to Ghostscript