Pic

Pic. A family of graphics file formats primarily associated with the Macintosh operating system and its native QuickDraw imaging model. Originally introduced as the PICT format with the first Macintosh 128K in 1984, it served as the fundamental metafile format for the Classic Mac OS for over a decade. The format is capable of containing both vector graphics instructions and raster graphics bitmap data, making it versatile for applications ranging from simple clipboard exchanges to complex page layout.

Definition and etymology

The term "PICT" is a direct abbreviation for "**Pic**ture," a naming convention that reflects its straightforward purpose as a container for graphical data. The format was intrinsically linked to the QuickDraw graphics library, the core rendering engine developed by Bill Atkinson and the Apple Lisa team. As a metafile format, a PICT file essentially stores a sequence of QuickDraw commands that can be replayed to reconstruct an image, similar in concept to the PostScript page description language but operating at a lower, system-specific level. This design made it the default format for inter-application graphics exchange on the Classic Mac OS, much like the role Windows Metafile (WMF) played on the Microsoft Windows platform.

Types and formats

There are two primary versions of the format, often distinguished by their internal structure and capabilities. The original PICT format, sometimes called PICT 1, was relatively simple and limited to a fixed set of QuickDraw operations. With the introduction of Color QuickDraw and system software updates, the more advanced PICT 2 format emerged, supporting deeper color depths including 8-bit palettes, 16-bit, and 32-bit RGB data, and expanded command sets. While the `.pic` and `.pict` filename extensions are common, the format is also frequently embedded within other file types, such as the resource fork of a Macintosh File System document. Its hybrid nature allows it to encapsulate both object-oriented vector elements, like those created in MacDraw, and pixel-based images from programs like MacPaint.

Uses and applications

The primary historical use was as the universal graphics clipboard format on the Mac OS, enabling seamless copying and pasting of images between diverse applications like Adobe Photoshop, QuarkXPress, and Microsoft PowerPoint. It was also extensively used for storing screen captures and for embedding graphics within documents created by word processors such as Microsoft Word and AppleWorks. In professional publishing and prepress workflows during the late 1980s and early 1990s, PICT files, often containing EPS data as a comment, were a common intermediary format for moving images into Aldus PageMaker or Adobe Illustrator. Furthermore, its sequence-of-commands structure made it suitable for simple animations and slideshows in early presentation software.

Technical specifications

A PICT file begins with a 512-byte header, followed by the image data structured as a series of operational codes (opcodes) that define drawing commands like `LineTo`, `PaintRect`, or `CopyBits`. The `CopyBits` command is particularly crucial as it is the mechanism for embedding compressed or uncompressed bitmap data within the metafile. Compression schemes supported include the proprietary Apple lossless Run-length encoding (RLE) for 1- to 8-bit data. The coordinate system is based on QuickDraw's internal measurement unit, the "**pic**t," which maps to the screen's pixel grid. Color handling evolved from monochrome to supporting color lookup tables (CLUT) and direct RGB values, with maximum dimensions theoretically limited by QuickDraw's 32-bit coordinate space.

History and development

The format was created by Apple Computer engineer Bill Atkinson as an integral part of the Macintosh project, debuting with the original Macintosh 128K in January 1984. Its development was parallel to the creation of the QuickDraw library and the LisaGraf system on the Apple Lisa. For years, it remained the cornerstone of Macintosh graphics, with significant enhancements arriving with System 6 and System 7 to support color and new QuickDraw features. Its prominence began to wane in the mid-1990s with the rise of cross-platform formats like JPEG, GIF, and PNG, and the introduction of the more advanced, portable PDF by Adobe Systems. The transition to macOS and the Carbon API, which deprecated QuickDraw in favor of modern technologies like Quartz, ultimately relegated the PICT format to legacy status, though support for reading the format persists for compatibility.

Category:Graphics file formats Category:Apple Inc. software Category:Macintosh