Section
Tools & Formats
Reference explanations of printing-related tools, formats, and standards.
Reference pages on document-system formats, queues, and protocols. The infrastructure layer that the printer connects to and the document moves through.
Document infrastructure map
The layer the document moves through
Formats, queues, and protocols connect the application to the page. These reference entries document the infrastructure beneath the visible printer.
- PDFThe portable document format the office standardised on.
- Searchable PDFA scanned image made selectable and indexable through OCR.
- OCROptical character recognition — turning an image of text into text.
- Print queueThe ordered line of jobs waiting for a shared device.
- Print spoolerThe service that holds and releases jobs to the device.
- Print driverThe translation layer between an application and a printer.
- Print serverThe system that administers a shared printer for many users.
- PostScriptThe page-description language behind PDF's lineage.
Future reference topics
- Document compression (ZIP / archive formats)
- File-format conversion
printing protocols
ToolT.38 Fax Relay (Fax over IP)ITU-T Recommendation T.38 defines procedures for real-time Group 3 facsimile communication over IP networks. It does not turn a fax into a network document format and it does not send the call as audio. Instead it takes the call apart: a gateway on the sending side demodulates the V.21 control channel and the V.27ter, V.29 or V.17 image carrier to recover the underlying T.30 bit stream, packetises that stream as Internet Facsimile Protocol (IFP) packets, and a gateway on the receiving side re-modulates it into a fresh analogue conversation with the terminal at its end. The two fax machines never speak to each other. Each speaks to a gateway that is impersonating the telephone line it still believes it is connected to — and every characteristic failure mode of fax over IP is a seam in that impersonation.
- Bonjour / mDNS Printer DiscoveryHow Bonjour, Multicast DNS (RFC 6762) and DNS-Based Service Discovery (RFC 6763) let devices find network printers automatically on the local link.Tool10
- SMB PrintingHow printing works over Server Message Block (SMB/CIFS): shared print queues, the Windows spooler, RPRN, Point-and-Print, and Samba.Tool12
- CUPS (Common UNIX Printing System)CUPS is the standards-based, open-source printing system for Linux, macOS, and UNIX-like operating systems, built on the Internet Printing Protocol (IPP).Tool7
- MopriaMopria is a vendor-neutral standard and certification program for driverless mobile and desktop printing and scanning, built on IPP.Tool14
- AirPrintAirPrint is Apple's driverless printing feature that submits print jobs over a local network using IPP and Bonjour, without printer-specific drivers.Tool7
- HP JetDirectHP JetDirect is Hewlett-Packard's print-server hardware and the raw TCP/IP (port 9100) method for attaching a printer directly to a network.Tool8
- LPD / LPR — Line Printer Daemon ProtocolLPD/LPR is the Berkeley line printer daemon protocol (RFC 1179, TCP port 515) for submitting print jobs to and managing the queue of a remote spooler.Tool7
- IPP (Internet Printing Protocol)Encyclopedic reference on the Internet Printing Protocol (IPP): its RFCs, HTTP-based model, IPP Everywhere, driverless printing, and STD 92.Tool14
print imaging
- Black Generation (GCR, UCR, and Black Separation)Black generation decides how CMYK separations use the black (K) channel. How GCR, UCR, and UCA trade cyan, magenta, and yellow for black, and the print tradeoffs.Tool4
- Dot Gain (Tone Value Increase)Dot gain, or tone value increase (TVI), is the growth of halftone dots between file and print: mechanical and optical causes, measurement, compensation.Tool3
- Moiré Patterns in PrintingHow moiré patterns arise in halftone printing from overlapping periodic screens, plus subject and scanning moiré, and the methods used to control them.Tool6
- Halftone Screen AnglesHalftone screen angles rotate each CMYK separation to prevent moire: the conventional 30-degree separation, yellow's 15-degree case, and supercell screening.Tool5
- Ordered DitheringOrdered dithering renders continuous tone on limited-color devices by comparing each pixel to a threshold from a small matrix tiled across the image.Tool4
- Error Diffusion DitheringError diffusion dithering quantizes each pixel and spreads the residual to neighbors. Floyd–Steinberg kernel, variants, scan order, artifacts, and tradeoffs.Tool6
- Frequency Modulation (FM / Stochastic) ScreeningFrequency modulation (FM) or stochastic screening renders tone by varying the number and placement of tiny, near-uniform halftone dots rather than their size.Tool5
- Amplitude Modulation (AM) ScreeningAmplitude modulation (AM) screening: how conventional halftone screens vary dot size on a fixed grid, plus screen ruling, angles, moire, and rosette patterns.Tool5
scanning standards
- ISIS (Image and Scanner Interface Specification) Scanner DriverISIS is a proprietary, royalty-bearing scanner-control interface for high-volume production document capture, now maintained by OpenText.Tool9
- eSCL / Driverless Scanning (AirScan, Mopria Scan)eSCL is an XML-over-HTTP driverless scanning protocol, discovered via mDNS/DNS-SD, used by Apple AirScan, Mopria Scan, and Linux SANE.Tool13
- ICA (Image Capture on macOS)How Apple's Image Capture Architecture (ICA) and the ImageCaptureCore framework let macOS discover and control scanners and cameras.Tool12
- SANE (Scanner Access Now Easy)SANE is the open, standardized API and network protocol that provides uniform access to scanners on Linux and other Unix-like systems.Tool12
- WIA (Windows Image Acquisition)Windows Image Acquisition (WIA): Microsoft's still-image capture platform for scanners and cameras — architecture, history, STI/TWAIN ties, and limits.Tool10
- TWAINTWAIN is the industry-standard API and protocol that lets imaging software acquire images from scanners through a vendor-supplied Data Source.Tool14
color and imaging
- Raster Image Processor (RIP)Encyclopedic reference on the raster image processor: how a RIP converts PostScript, PDF, or XPS page descriptions into device-ready raster output.Tool5
- HalftoningHalftoning simulates continuous-tone images using patterns of dots on bi-level printing devices. History, AM vs FM screening, PostScript and PDF halftones.Tool8
- CMYK Color ModelCMYK is the subtractive four-ink color model (cyan, magenta, yellow, key/black) used in process color printing and ICC-managed prepress workflows.Tool8
- ICC Color ProfilesICC color profiles are ISO 15076-standardized files that characterize device color so it translates consistently across scanners, displays, and printers.Tool9
document standards
- TIFF (Tagged Image File Format)A tag-based container format for raster images, developed in the desktop-publishing era and standardized at Revision 6.0 (1992), now owned by Adobe.Tool10
- ISO 32000 (PDF)ISO 32000 is the ISO standard for the Portable Document Format (PDF): its history, structure, print pipeline role, and PDF 1.7 vs PDF 2.0.Tool14
- PDF/UA (ISO 14289)PDF/UA (ISO 14289) is the international standard defining how PDF files must be structured to be reliably accessible to assistive technology.Tool9
- PDF/XPDF/X is the ISO 15930 family of print-ready PDF subsets that constrain fonts, color, and page geometry for reliable prepress data exchange.Tool14
- PDF/APDF/A (ISO 19005) is the archival subset of PDF for long-term preservation, using embedded fonts, device-independent color, and standardized metadata.Tool7
page description languages
- AFP (Advanced Function Presentation)Advanced Function Presentation (AFP): IBM-originated, now open, architecture (MO:DCA + IPDS) for high-volume, integrity-critical variable-data printing.Tool13
- XPS (XML Paper Specification)Microsoft's XML/ZIP-based fixed-layout document format, print spool format, and page description language, standardized as OpenXPS (ECMA-388).Tool14
- PJL (Printer Job Language)Printer Job Language (PJL) is HP's job-level control language for switching printer PDLs and reading printer status back to the host.Tool9
- HP-GL (Hewlett-Packard Graphics Language)HP-GL is Hewlett-Packard's vector command language for pen plotters; HP-GL/2 became the vector-graphics layer of PCL 5.Tool6
- ESC/POSEpson's byte-oriented control command language for point-of-sale receipt and thermal printers, cash drawers, and related retail peripherals.Tool7
- ESC/P (Epson Standard Code for Printers)ESC/P is Epson's escape-sequence printer control language for dot-matrix and inkjet printers, spanning ESC/P 2, ESC/P-R, and ESC/POS.Tool8
- PCL (Printer Command Language)Hewlett-Packard's escape-sequence and binary printer-control language family (PCL 1-6), the office-printing counterpart to PostScript.Tool5
- PostScriptPostScript is Adobe's device-independent page-description language and stack-based programming language that launched desktop publishing in the 1980s.Tool11
document workflows