Next-generation PDF format for imaging unveiled

The TWAIN Working Group (TWG) and the PDF Association , both not-for-profit organizations designed to foster universal public standards, have announced the joint publication of PDF/raster 1.0 , a subset of the PDF specification suited to the needs of resource-constrained imaging systems.

PDF/raster is a strict subset of the PDF file format. It was designed for storing, transporting and exchanging multi-page raster-image documents, especially scanned documents. PDF/raster provides the portability of PDF while offering the core functionality and support of TIFF.

Bitonal, grayscale and RGB images are supported. Compression options include JPEG, lossless CCITT Group 4 Fax and uncompressed.

PDF/raster was created via a collaboration between the TWAIN Working Group, which originated the PDF/raster concept, and the PDF Association, which provided PDF technology expertise and perspective as well as means of communicating with the PDF software industry to ensure a diverse range of relevant viewpoints was represented. 

PDF/raster is part of the TWAIN Working Group’s new TWAIN Direct specification — the first zero-footprint, cloud-based version of its royalty free open standard protocol that allows applications to talk directly to document scanners without the need for vendor specific drivers.  

PDF/raster provides image-only file format guidelines that can be implemented across a wide range of scanners. It is designed to be efficient to implement on any scanner, to be easy to parse by applications, and to be 100% compatible with PDF and PDF-consuming applications.

“Working with the experts from the PDF Association helped us to avoid many development problems and ensured the standard’s quality,” said Jon Harju, CTO of Visioneer and the TWAIN Working Group’s Chair and lead on the project.

“We have now developed a new PDF file format that can be easily implemented across a wide range of scanners, and is featured as the preferred file format in our new TWAIN Direct specification. Working with the PDF Association on this project was an amazing experience and allowed us to turn out a solid PDF/raster specification for adoption in the imaging market.”

“We’re very pleased to have worked with the TWAIN Working Group on this project,” said Olaf Drümmer, a Managing Director of callas software and the PDF Association’s technical lead on development of PDF/raster as well as the organization’s former Chairman.

“We think PDF/raster is a critical step in paving the way to adoption of PDF as the native file-format for image acquisition,” he said.

Although for imaging purposes PDF/raster imposes many restrictions on PDF content and layout, implementers gain from the following benefits:

  • files can be read and written without a full PDF parser or generator
  • files can be created efficiently from raster images
  • files can be generated using a fixed-size raster data buffer
  • less than 1KB is required per page in order to generate a multi-page file
  • images can be located and read efficiently with comparatively simple code
  • PDF/raster files can be quickly and easily identified as such by software
  • PDF/raster supports effective and readily available compression algorithms
  • PDF/raster has important advantages over the full PDF format for storing scanned documents:
  • the exact original raster image data can be recovered
  • a complex rendering engine is not required
  • it provides a precise, well-defined target, simplifying engineering design and testing


PDF/raster retains optional PDF security and authentication features useful for protecting content in a variety of implementations:

  • encryption is allowed, useful for access-control purposes
  • digital signatures are allowed, useful for authenticating content and for applications that require verification of the document origin, authenticity, date or time of creation, and so on


PDF/raster has important advantages over TIFF and JPEG for storing scanned documents:

  • Compared to TIFF, it has far fewer and simpler variants.
  • Compared to TIFF, compression is simpler and better standardized and supported.
  • Compared to TIFF, PDF files can be natively viewed and printed on more platforms.
  • Unlike JPEG, it is natively multi-page and handles bitonal images


An open industry standard, PDF/raster is available royalty-free, and may be freely download from both the PDF Association ( ) and the TWAIN Working Group ( ).