The PICT file (.pict, .pct, .pic)

PICT is the picture format of QuickDraw, the graphics engine of the classic Mac OS. When a program drew into a QuickDraw picture, QuickDraw recorded each command (a line, a filled rectangle, a run of text, a bitmap) as an opcode with its data. Playing the picture back with DrawPicture repeated those commands, at any size. That makes PICT a metafile: like PDF or EPS, it can hold vector shapes and text as well as pixels.

On classic Macs PICT was everywhere. A picture could be saved as a file of type PICT, stored as a PICT resource inside any file, or put on the clipboard, where PICT was one of the two standard formats, next to plain text. Copying a drawing from one program and pasting it into another went through PICT.

When Apple moved to Mac OS X, PDF became the native metafile format and QuickDraw was phased out. You meet PICT files today in archives of 1980s and 1990s Mac work: clip art, scans, diagrams, illustrations from old desktop publishing projects and graphics inside old documents.

A picture is picSize, picFrame and then a list of opcodes. Here is Apple's own example of a small version 1 picture, decompiled, from Inside Macintosh. It fills a rectangle and an oval with patterns and paints a triangle, in 79 bytes:

$"004F"                 /* picture size: 79 bytes */
$"0002 0002 006E 00AA"  /* bounding rectangle */
$"11" $"01"             /* version 1 */
$"01" $"000A" $"0002 0002 006E 00AA"   /* clip region */
$"0A" $"77DD 77DD 77DD 77DD"           /* fill pattern */
$"34" $"0002 0002 006E 00AA"           /* fillRect */
$"0A" $"8822 8822 8822 8822"           /* fill pattern */
$"5C"                                  /* fillSameOval */
$"71" $"001A" …                        /* paintPoly: a polygon */
$"FF"                                  /* end of picture */

A few opcodes you'll see in version 2 pictures:

Version 2 opcodes are words, and odd-sized data is followed by a zero byte so the next opcode starts on an even byte. Many opcodes are reserved, with sizes defined by rule, so an old reader can skip opcodes it doesn't know. Comments (00A0, 00A1) let applications store extra data, such as the original drawing objects, that other programs ignore.

The 512-byte header exists only in PICT files: Apple's documentation says the data fork of a PICT file begins with 512 bytes the application can use for its own purposes, followed by the picture. The same picture as a resource or on the clipboard starts straight with picSize. That's why file-type databases look for the version opcode at byte 522 (512 + 2 for the size + 8 for the frame), and why a PICT extracted from a resource needs 512 bytes added in front before most programs will open it.

• Mac OS X replaced PICT with PDF as the native metafile format, though many applications kept reading PICT because it was so common.
• QuickDraw was deprecated in Mac OS X 10.4 Tiger and never made available to 64-bit programs. From then on, 64-bit software could only convert PICT data through a 32-bit helper process. As Mac software went 64-bit, and 32-bit code was removed altogether, built-in PICT support grew patchy.
• Preview is unreliable with PICT files. The 64-bit Preview in Mac OS X 10.6 already reported PICT as unsupported, and users of later macOS versions report files that won't open or show up blank. Apple hasn't documented when or how support changed, so don't count on it.
• Photoshop can still open PICT files that contain only bitmaps, but not those built from QuickDraw drawing objects, and it can no longer save PICT.
• GIMP has never supported PICT.

PDF is PICT's direct successor on the Mac. To preserve an old PICT, convert drawings to PDF or SVG and bitmaps to PNG or TIFF, keeping the original file alongside.

• LibreOffice (Windows, macOS, Linux) opens PICT files in Draw. From there, export as PDF or SVG to keep a drawing as vectors, or as PNG. On the command line, soffice --headless --convert-to pdf picture.pct does it without opening a window.
• ImageMagick reads PICT files that hold bitmaps, which covers most scans and screenshots: magick picture.pict picture.png (convert in ImageMagick 6). It needs the 512-byte header.
• GraphicConverter, a long-running Mac image tool, opens and batch-converts PICT files on current macOS.
• Photoshop opens bitmap-only PICTs; save them as PNG or TIFF.
• Classic Mac OS in an emulator is the last resort for drawings that only the original application (MacDraw, Canvas, ClarisDraw) renders correctly: open them there and export.

• The file has no extension. Classic Mac OS identified files by a hidden four-letter type code, not an extension, and that code is lost when files pass through other systems. Look for 00 11 02 FF or 11 01 at byte 522, then add .pict.
• It opens blank, white or not at all. The program only reads bitmaps and the picture is a drawing, or the program has no PICT support any more. Try LibreOffice.
• Text looks wrong. QuickDraw text refers to fonts by Mac font names and old Mac character sets. Missing fonts are replaced, and accented characters can come out wrong. Check text after converting.
• Images inside are missing. Bitmaps compressed with QuickTime (opcode 8200) need a QuickTime-aware reader. Not every converter has one.
• Lines and shapes are jagged after converting. The converter rasterised the drawing. Export as PDF or SVG from LibreOffice to keep vectors.

A PICT file contains drawing commands and comments, not scripts. Treat old files from unknown sources like any other complex binary: keep converters updated, since parsing a long list of opcodes with lengths and regions is the kind of code where bugs hide.