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BITMAP(6)                        Games Manual                        BITMAP(6)



NAME
       bitmap - external format for bitmaps

SYNOPSIS
       #include <&lt;libg.h>&gt;

DESCRIPTION
       Bitmaps  are described in graphics(2).  Fonts and bitmaps are stored in
       external files in machine-independent formats.

       Bitmap files are read and written using rdbitmapfile  and  wrbitmapfile
       (see  balloc(2)).  A bitmap file starts with 5 decimal strings: ldepth,
       r.min.x, r.min.y, r.max.x, and r.max.y.  Each number is right-justified
       and  blank  padded  in 11 characters, followed by a blank.  The rest of
       the file contains the r.max.y-r.min.y rows of bitmap data.  A row  con-
       sists  of the byte containing pixel r.min.x and all the bytes up to and
       including the byte containing pixel r.max.x-1.  A pixel with  x-coordi-
       nate  = x in a bitmap with ldepth = ld will appear as w = 2^ld contigu-
       ous bits in a byte, with the pixel's high order  bit  starting  at  the
       byte's  bit  number  w*(x mod (8/w)), where bits within a byte are num-
       bered 0 to 7 from the high order to the low order bit.  If w is greater
       than 8, it is a multiple of 8, so pixel values take up an integral num-
       ber of bytes.  Rows contain integral number of bytes, so there  may  be
       some unused pixels at either end of a row.

       The  rdbitmap  and  wrbitmap functions described in balloc(2) also deal
       with rows in this format, stored in user memory.

       Some small images, in particular 48x48 face files as  used  by  seemail
       (see  mail(1)) and 16x16 cursors, can be stored textually, suitable for
       inclusion in C source.  Each line of text represents one scan line as a
       comma-separated  sequence  of  hexadecimal bytes, shorts, or words in C
       format.  For cursors, each line defines a pair of bytes.  (It takes two
       images  to  define  a cursor; each must be stored separately to be pro-
       cessed by programs such as tweak(1).)  Face files of one bit per  pixel
       are  stored  as  a sequence of shorts, those of larger pixel sizes as a
       sequence of longs.  Software that reads these  files  must  deduce  the
       image  size  from the input; there is no header.  These formats reflect
       history rather than design.

SEE ALSO
       tweak(1), graphics(2), bitblt(2), balloc(2), face(6), font(6)



                                                                     BITMAP(6)