Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!sdd.hp.com!decwrl!ucbvax!bloom-beacon!eru!luth!sunic!mcsun!hp4nl!nikhefk!keeshu
From: keeshu@nikhefk.UUCP (Kees Huyser)
Newsgroups: comp.sys.mac.wanted
Subject: Re: Format for MacPaint images
Keywords: MacPaint images
Message-ID: <774@nikhefk.UUCP>
Date: 29 Aug 90 12:00:42 GMT
References: <1443@unicorn.WWU.EDU>
Sender: keeshu@nikhefk.uucp (Kees Huyser)
Reply-To: keeshu@nikhefk.UUCP (Kees Huyser)
Organization: the National Institute for Nuclear Physics; Netherlands
Lines: 66

In article <1443@unicorn.WWU.EDU> n8541751@unicorn.WWU.EDU (Where there is darkness, light) writes:
#Does anyone have format documentation for MacPaint images, or know where it 
#can be FTP'd?  
#Kris Bruland

This comes from TechNote 086, try to get your hands on this one for more info.
===================
MacPaint documents have a file type of PNTG, and since they use only the data 
fork, you can ignore the resource fork.  The data fork contains a 512Pbyte 
header followed by compressed data which represents a single bitmap (576 pixels 
wide by 720 pixels tall).  At a resolution of 72 pixels per inch, this bitmap 
occupies the full 8 inch by 10 inch printable area of a standard ImageWriter 
printer page.

Header

The first 512 bytes of the document form a header of the following format:

  %  4Pbyte version number (default = 2)
  %  38*8 = 304 bytes of patterns
  %  204 unused bytes (reserved for future expansion)

As a Pascal record, the document format could look like the following:

    MPHeader = RECORD
        Version:     LONGINT;
        PatArray:    ARRAY [1..38] of Pattern;
        Future:      PACKED ARRAY [1..204] of SignedByte;
    END;

If the version number is zero, the document uses default patterns, so you can 
ignore the rest of the header block, and if your program generates MacPaint 
documents, you can write 512 bytes of zero for the document header.  Most 
programs which read MacPaint documents can skip the header when reading.

Bitmap

Following the header are 720 compressed scan lines of data which form the 576 
pixel wide by 720 pixel tall bitmap.  Without compression, this bitmap would 
occupy 51,840 bytes and chew up disk space pretty fast; typical MacPaint 
documents compress to about 10K using the _PackBits procedure to compress runs 
of equal bytes within each scan line.  The bitmap part of a MacPaint document 
is simply the output of _PackBits called 720 times, with 72 bytes of input each 
time.

To determine the maximum size of a MacPaint file, it is worth noting what 
Inside Macintosh says about _PackBits:

    The worst case would be when _PackBits adds one byte to the row
    of bytes when packing.

If we include an extra 512 bytes for the file header information to the size of 
an uncompressed bitmap (51,840), then the total number of bytes would be 
52,352.  If we take into account the extra 720 potential bytes (one for each 
row) to the previous total, the maximum size of a MacPaint file becomes 53,072 
bytes.
=========================
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