Fresh Fish 4/FreshFish_May-June1994.bin/bbs/amigalib/d985/newiff.lha/NewIFF/NewIFF.ReadMe

Text File | 1994-04-05 | 12.2 KB | 280 lines

                 NewIFF39: IFF Modules with AA Support


The NewIFF39 code modules and examples based on iffparse.library are
designed as replacements for the original EA IFF code.  The object code
modules (with source provided) contain many high-level support functions
for reading and writing IFF files and clipboard data, and for loading,
saving, and displaying ILBM files in a 1.3 through 3.0/AA compatible manner.
In some modules, it has been possible to retain much of the original
EA IFF code.  However, most structures and most higher level function
interfaces have changed.

On the plus side, these new modules contain many easy-to-use functions
for querying, loading, displaying, and saving ILBMs.  During their
development, modules similar to these have been used inhouse at Commodore
for the Display program and several other ILBM applications.
The screen.c module provides powerful display-opening functions which are
1.3-compatible yet provide a host of new options under 2.0 and 3.0 such
as centered overscan screens, full-video display clips, border transparency
control, and autoscroll.  This 39.x releases of the NewIFF code also support
V39 and the AA chipset for full 8-bit-per-gun color and AA modes.
Modules are provided for printing (screendump) and for preserving or
adding chunks (copychunks). And the 8SVX example now actually plays samples
and instruments.  In addition, clipboard support is automatic for all
applications that use the IFFP modules because parse.c's openifile()
interprets the filename -c[n] (ie. "-c", "-c1", "-c2", etc.) as clipboard
unit n.

All of the applications with the NewIFF code require iffparse.library
which has been part of the OS since Workbench 2.0.  Please note that
the 2.04 Workbench version of iffparse.library is a 1.3-compatible library,
and that all of the modules and examples (with the exception of Save8)
have been designed to take advantage of 2.0/3.0, but also work under 1.3.
Developers who wish to distribute iffparse.library on their commercial
products may execute a 2.0 Workbench license, or may get an amendment to
their 1.3 Workbench license to allow distribution of iffparse.library.


The NewIFF39 modules contain enhanced code in many areas to take
advantage of 2.0 and 3.0 features while remaining functional under
1.3 (with 2.04 iffparse.library).  In addition, great effort has been
put into identifying and replacing any code sections which were
inflexible or not upwards compatible.  The code implements 32-bit
CAMG, display database aspect ratios, 8-bit CMAP from 4, 8, or 32-bit
color data, mode fallback when an ILBM's display mode is not available,
overscan centering (except under 1.3) based on the user's closest
Preference setting with display clips properly constrained to maximum
limits, setting of as many colors as the destination can handle,
default detection and adjustment of old 4-bit left-shifted CMAP values,
and built-in support for up to 24 planes of data plus a Mask plane.
Note that currently, the 24 planes plus 1 mask plane limit is hardcoded,
but we expect to make this more flexible in a future release of the code,
perhaps also adding alpha channel support.


Through the use of tag-like arrays of desired chunk ID's, applications
can control which chunks are gathered by the parsing module.  It is also
possible to clone chunks for rewriting and for applications to add chunks
to written FORMs.  Applications may also pass additional screen tags
to the display-opening module (screen.c) and may control much of this
module's default behavior through flags (see iffp/ilbmapp.h of NewIFF39).


Most of the high-level function pairs provided in these modules have
been designed to provide safe cleanup for themselves.  For example,
a loadbrush() that succeeds or fails at any point can be cleaned up
via unloadbrush.  The cleanup routines null out the appropriate
pointers so that allocations will not be freed twice.


All applications use the parse.c module.  The basic steps
for using the parse.c module are:

    o Define tag-like arrays of your desired chunks (readers only)

    o Allocate one or more [form]Info structures as defined in
      iffp/[form]app.h (for example an ILBMInfo defined in
      iffp/ilbmapp.h).

    o Initialize the ParseInfo part of these structures to the
      desired chunk arrays, and to an IFFHandle allocated via
      iffparse AllocIFF().

    o Use the provided high level load/save functions, or use the
      lower level parse.c openifile(), reader-only parseifile()/
      getcontext()/nextcontext(), and closeifile().  The filename
      -c[n] may be used to read/write clipboard unit n.

    o Clean up, FreeIFF(), and deallocate [form]Info's.


V39/AA Support

For NewIFF39, the ILBMInfo was extended to support a 32-bit-per-gun
representation of the CMAP for use with the V39 color setting
functions.

/* --- New --- */
WORD  *colorrecord;     /* Passed to LoadRGB32 (ncolors,firstreg,table) */
Color32 *colortable32;  /* 32-bit-per-gun representation of colors      */
ULONG crecsize;         /* Bytes allocated including colorrecord WORDs  */


For compatibility, the old style WORD array colortable of xRGB 4-bit values
is still created for all loaded ILBMs.
But the NewIFF39 code will also automatically allocate and create the 32-bit
color table under V39 or higher, unless the calling application asks it
not to by setting IFFPF_NOCOLOR32 in ILBMInfo->IFFPFlags:

/* Don't allocate or use a 32-bit-per-gun Color Table under V39 or above */
#define IFFPB_NOCOLOR32 0
#define IFFPF_NOCOLOR32 (1L << IFFPB_NOCOLOR32)


By default, the NewIFF39 code will examine the low nibbles
of an ILBM.CMAP to determine if it is an old-style left-shifted
4-bit-per-gun CMAP, and if all of the low nibbles of all usable
registers are zero, the code will assume a 4-bit CMAP and scale the 4-bit
values properly to 32 bits.  This CMAP examination is disabled if
either the ILBM.BMHD->Flags contains the flags BMHDF_CMAPOK (1L << 7),
OR if the calling application passes the IFFPF_CMAPOK flag in
ILBMInfo->IFFPFlags.  In either of these cases, the 8-bit CMAP
values will be accepted as-is, and scaled to 32 bits.


Since V37, the NewIFF code has supported saving of 8-bit-significant
CMAP data, and the function interface will accept 4-bit, 8-bit, or
32-bit per gun color data.


Currently, the NewIFF code does not make use of V39 Datatypes,
and therefore has does not have the capability to load non-IFF file formats.
You may wish to link with the NewIFF modules but also add conditional
application code to make use of Datatypes when datatypes.library is
present.  This would allow you program to be backwards compatible
while taking even greater advantage of V39.


Locale Support

The NewIFF39 code does not use locale.library as-is.  However, the code
is prepared for localization.  A catalog file of all module strings
is provided (iffp.cd), and the module include file iffpstrings.h is
generated from this iffp.cd file using CatComp 39.x.  All string handling
for the modules has been centralized in modules/iffpstrings.c which
includes comments regarding locale support.  See the Locale.Readme
in the NewIFF39 archive for additional tips on writing localized
IFF applications.


IMPORTANT NOTES

o Clipboard and File Handles

    Most of the higher-level load functions keep the
    IFFHandle (file or clipboard) open.  While the handle is
    open, you may use parse.c functions (such as findpropdata)
    OR direct iffparse functions (FindProp(), FindCollection())
    for accessing the gathered chunks.  However, it is not a good
    idea to keep a filehandle OR the clipboard open.  While
    a clipboard unit is open, no other applications can clip
    to the unit.  And while a file is open, you can't write the
    file back out.  So, instead of keeping the file or unit
    open, you can use copychunks (in copychunks.c) to create
    a copy of your gathered chunks, and do an early closeifile()
    (parse.c).  Then access and later write back out (if you wish)
    and deallocate your copied chunks via the routines in the
    copychunks module (findchunk, writechunklist, freechunklist).

o Complex Forms

        The parse.c module will enter complex formats such as
    CATSs, LISTs, and nested FORMs to find the FORM
    that you are interested in.  This is great.  However, if you are
        a read-modify-write program, you should warn your user when this
        occurs unless YOU are capable of recreating the complex format.
    Otherwise, your user may unknowingly destroy his complex file
    by writing over it with your program.  Example - a paint
    program could read an ILBM out of a complex LIST containing
    pictures and music, and then save it back out as a simple ILBM,
    causing the user to lose his music and other pictures.
    To determine if a complex form was entered after a load,
    check the (form)Info.ParseInfo.hunt field.  If TRUE (non-zero),
    then your file was found inside a complex format.



        LIST OF IFFP MODULES AND APPLICATIONS
                =====================================
    NOTE - Some useful functions are listed with each module
        See module source code for docs on each function.
        See application examples for usage.

APPLICATIONS (these require linkage with modules - see Makefiles)
============
ILBMDemo    Displays an ILBM, loads a brush, saves an ILBM, opt. print
ILBMLoad    Queries an ILBM and loads it into an existing screen
ILBMtoC        Outputs an ILBM as C source code
ILBMtoRaw    Converts an ILBM to raw plane/color file
RawtoILBM    Converts raw plane/color file (from ILBMtoRaw) to an ILBM
24bitDemo    Saves a simple 24-bit ILBM and then shows it 4 planes at
        a time (if given filename, just does the show part)
Play8SVX    Reads and plays an 8SVX sound effect or instrument
          - LoadSample, UnloadSample, PlaySample, OpenAudio,
            CloseAudio, and body load/unpack functions
PlaySMUS    Just a skeleton for a SMUS player - it loads the SMUS
        and samples.
ScreenSave    Save the front screen or viewport as an ILBM, with an icon
Save8        Create and save an 8-plane 256 color screen (V39/AA)


OTHER EXAMPLES (use iffparse.library directly and require no modules)
==============
Sift        Checks and prints outline of any IFF file (uses RAWSTEP)
ILBMScan    Prints out useful info about any ILBM
ClipFTXT    Demonstrates simply clipping of FTXT to/from clipboard
apack.asm    Dr. Gerald Hull's assembler replacement for packer.c
unpacker.asm    An assembler replacement

ALSO PROVIDED
=============
Display        1.3 through 3.0 compatible ILBM display and slideshow
        program - supports AA.
bumprev        updated version of bumprev revision file creation utility

GENERAL IFFPARSE SUPPORT MODULE
===============================
parse.c        File/clipboard IO and general parsing
          - openifile, closeifile, parseifile, getcontext,
            nextcontext, contextis, currentchunkis, PutCk chunk
            writing function, and IFFerr text error routine

iffpstrings.c   Centralized string and message handling for modules.

ILBM READ MODULES
=================
loadilbm.c    High level ILBM load routines which are passed filenames
        (calls getbitmap)
          - loadbrush/unloadbrush, loadilbm/unloadilbm, and queryilbm
getbitmap.c    brush/bitmap loading (non-display, calls ilbmr.c)
          - createbrush/deletebrush, getbitmap/freebitmap
getdisplay.c    bitmap load/display (calls screen.c, ilbmr.c)
          - showilbm/unshowilbm, createdisplay/deletedisplay
screen.c    1.3/2.0/3.0 AA/ECS/non-ECS compatible screen/window module
          - opendisplay, openidscreen, modefallback, clipit
ilbmr.c        Lower level ILBM body/color load routines (calls unpacker.c)
          - loadbody, loadcmap, getcolors/freecolors,
            alloccolortable, getcamg (gets or creates modeid)
unpacker.c    BODY unpacker


ILBM WRITE MODULES
==================
saveilbm.c    High level ILBM saving routines which are passed filenames
        (calls ilbmw.c)
          - screensave and saveilbm
ilbmw.c        Lower level ILBM body/color save routines (calls packer.c)
          - InitBMHD, PutCMAP, PutBODY
packer.c    BODY packer


EXTRA MODULES
=============
copychunks.c    Chunk cloning and chunk list writing routines
          - copychunks, findchunk, writechunklist, freechunklist
screendump.c    Screen printing module (iffparse not required)
bmprintc.c    Module to output ILBM as C code


INCLUDE FILES
=============
iffp/#?.h    This subdirectory may be kept in your current directory
        or in your main include directory.


Thanks to Steve Walton for his code changes for Manx/SAS compatibility,
and to Bill Barton and John Bittner for their comments and suggestions.