Path: utzoo!utgpu!water!watmath!clyde!rutgers!mit-eddie!uw-beaver!apollo!oj
From: oj@apollo.uucp (Ellis Oliver Jones)
Newsgroups: comp.sys.apollo
Subject: Re: GPR Bitmap File format
Message-ID: <3925c496.d5b2@apollo.uucp>
Date: 18 Dec 87 23:59:00 GMT
References: <8712091529.AA02789@ELI.CS.YALE.EDU>
Reply-To: oj@apollo.UUCP (Ellis Oliver Jones)
Organization: Apollo Computer, Chelmsford, MA
Lines: 48

In article <8712091529.AA02789@ELI.CS.YALE.EDU> ferguson@BKNLVMS.BITNET writes:
>Does anyone know the exact file format of [color] GPR bitmaps...?

The exact internal format is (obviously) around here someplace,
but it's not very pleasant to work with.  Have you tried gpr_$open_bitmap_file ?
It allows you to specify the parameters of a bitmap file, then create it.
You get back (indirectly) a bunch of good stuff such as the location
of the storage, the number of bytes per line, etc. Once you have the
storage_offset and the bytes_per_line, you can scribble away into the
bitmap.   If you init GPR in no_display mode, you can write a bitmap
file without even disturbing your screen.

This works for multibit pixels at SR9.7 (and beyond...)  
Enjoy. /oj

Here are some of the relevant items from /sys/ins/gpr.ins.pas

            { external bitmap group header descriptor }
        gpr_$bmf_group_header_t =
            RECORD
            n_sects         : integer16;   <- you set this to 1
            pixel_size      : integer16;   <- you set this 1-32 (to 8 for pseudocolor)
            allocated_size  : integer16;   <- you set this to zero, it comes back w ACTUAL bits/pixel
            bytes_per_line  : integer16;   <- you set this to zero...GPR sets it for you )
            bytes_per_sect  : integer32;   <- ditto
            storage_offset  : univ_ptr;    <- ditto
            END;

            { array of external bitmap group header descriptors }
        gpr_$bmf_group_header_array_t =
            ARRAY [0..gpr_$max_bmf_group] OF gpr_$bmf_group_header_t;

...
{ GPR_$OPEN_BITMAP_FILE obtains access to an external bitmap }

PROCEDURE gpr_$open_bitmap_file (
              IN     access     : gpr_$access_mode_t;
              IN     filename   : UNIV name_$pname_t;   { pathname of bitmap file }
              IN     namesize   : integer;              { length of file name }
              IN OUT version    : gpr_$version_t;
              IN OUT size       : gpr_$offset_t;        { x,y size of bitmap }
              IN OUT groups     : integer;
              IN OUT g_headers  : gpr_$bmf_group_header_array_t;
              IN     attribs    : gpr_$attribute_desc_t;{ attributes bitmap is to have }
              OUT    bitmap     : gpr_$bitmap_desc_t;   { returned bitmap descriptor   }
              OUT    created    : boolean;              { TRUE if we created the file  }
              OUT    status     : status_$t 
          );EXTERN;