bld2ff.1

.Dd 2023-10-26
.Dt BLD2FF 1
.Os farbfeld-utils
.Sh NAME
.Nm bld2ff
.Nd convert MegaPaint BLD image to farbfeld
.Sh SYNOPSIS
.Nm
.Sh DESCRIPTION
.Nm
reads a MegaPaint BLD image from stdin, converts it to
.Xr farbfeld 5
and writes the result to stdout.
.Pp
MegaPaint BLD is the main native raster graphics format of MegaPaint. There were editions of
MegaPaint for Atari ST, MS-DOS, and Windows.
.Pp
In case of an error
.Nm
writes a diagnostic message to stderr.
.Sh EXIT STATUS
.Bl -tag -width Ds
.It 0
Image processed successfully.
.It 1
An error occurred.
.El
.Sh FORMAT DETAILS

The BLD format.
.Bd -literal -offset left
┌────────┬─────────────────┬──────────────────────────────────────────────────┐
│ Offset │ Type            │ Details                                          │
├────────┼─────────────────┼──────────────────────────────────────────────────┤
│    0   │ signed int16 BE │ Code for the image width and compression scheme. │
│        │                 │ Actual width is 1 + the a┐bsolute value of this  │
│        │                 │ field. If negative, image is compressed.         │
│    2   │ signed int16 BE │ Code for the image height. Actual height is 1 +  │
│        │                 │ the value of this field.                         │
│    4   │ bytes           │ The pixel data. After decompression if necessary │
│        │                 │ the format is 1 bit/pixel, white-is-zero. Rows   │
│        │                 │ are padded to the next byte boundary.            │
└────────┴─────────────────┴──────────────────────────────────────────────────┘
.Ed
.Pp
.Sh DECOMPRESSION ALGORITHM
.br
Read the next byte, follow the instructions below, repeat.
.Bd -literal -offset left
┌───────────────┬─────────────────────────────────────────────────────────────┐
│ Code byte (N) │ Instructions                                                │
├───────────────┼─────────────────────────────────────────────────────────────┤
│ N=0 or N=255  │ Read the next byte (C). Emit C+1 bytes of value N.          │
│ Any other     │ Emit 1 byte of value N.                                     │
└───────────────┴─────────────────────────────────────────────────────────────┘
.Ed
.Sh OPTIONS
The program takes no arguments.
.Sh EXAMPLES
$
.Nm
< image.bld > image.ff
.Pp
$
.Nm
< image.bld │ bzip2 > image.ff.bz2
.Sh SEE ALSO
.Xr bzip2 1 ,
.Xr farbfeld 5 ,
.Xr farbfeld-utils 7