Turnbull China Bikeride/Turnbull China Bikeride - Disc 2.iso/ACORNUSERS/CBSA/ART/INTERGIF/!InterGif/!Help

Text File | 1999-02-19 | 19KB | 446 lines

                    InterGif 6.07
                    =============

        by Peter Hartley (K) All Rites Reversed
    Desktop front-end adapted from one by Iain Logan

INTERGIF 6.07 is a program for making GIF images from 2-, 4-, 16-
or 256-colour RiscOS sprite files, or from Draw files, or from
files produced with Iota Software's (commercial) animation
program The Complete Animator. It can also convert from GIFs back
to sprites, and can also be used as an optimiser for animated
GIFs prepared in other programs.


        Get the latest version
        ----------------------

The latest version of InterGif, plus more help information and
full source code for various platforms, is always available on
the World-Wide Web at the NEW address
        http://utter.chaos.org.uk/~pdh/software/intergif.htm
It's the nineteenth of February, 1999, as I'm writing these
words: if it's long after that that you're reading them, you
might want to see if there's a later version now available.


        Distribution
        ------------

InterGif is NOT COPYRIGHTED and is NOT distributed under the GNU
General Public Licence. For full information read the file
!InterGif.Copying or go to the Web site.
    InterGif is mine: in particular, it doesn't belong to my
employers, ANT Limited. If it gets anything wrong, it's my
problem, not theirs.
    Versions 6 and later of InterGif contain (a small piece of)
code developed by the Independent JPEG Group. (The "Find best
palette" routine, if you must know.)
    In order to convert Draw files you will need Acorn's Drawfile
module. This is not included in InterGif distributions, but is
available from
        ftp://ftp.acorn.co.uk/


        Features
        --------

  o InterGif runs either on the desktop, or from the command line
    (so I can produce the GIFs for my own Web pages, from the
    sprites which constitute their source, using a make file!).

  o InterGif has options for the transparency and interleaving
    features of GIF89a.

  o InterGif can take a sprite file (or an Animator file)
    containing several frames, and produce from it an animated
    GIF which Netscape 2.0 or later, MSIE 3.0beta1 or later, or
    ANT Fresco 1.22 or later will render as animated if it's
    inlined in a Web page. The animation delay can be set
    individually for each frame, or for the whole animation.

  o InterGif will reduce its input to a smaller number of colours
    (unless you explicitly tell it not to) if it can get away
    with it, i.e. if only that many of the colours are used
    anyway.

  o It will also compress only the rectangle which has changed on
    each frame, so if your animation has a complex but stationary
    background, the background will only get compressed once.
    Deviousness and cunning are employed to minimise the final
    size of the GIF: so much so that many animated GIFs I've
    found on the Web have ended up smaller when run through
    InterGif.

  o It can also make GIF images from Draw files. It uses, for
    this, the same code that is in my AADraw program (see end),
    which means it produces GIFs or sprites with a 216-colour
    cube palette (as used on Macintoshes and by Netscape and MSIE
    for Windows), *not* the standard Acorn 256-colour palette.
    (For AADraw connoisseurs, I'll add that you don't get the -b
    feature of that program: InterGif always anti-aliases to
    white.)

  o InterGif 6 lets you forcibly reduce a GIF's palette to the
    standard Acorn 256-colour palette, or to a 216-entry colour
    cube (as used on the Macintosh and by most Windows browsers),
    or to a palette file you supply. Alternatively, it can
    calculate the best palette for displaying the GIF, and then
    reduce to that. (This is not the same as the colour reduction
    InterGif has always had: it is lossy and you should keep
    copies of your unmapped originals.)

  o InterGif 6.03 and later can pre-process each of your images
    using Acorn's ChangeFSI: see below for more details.


        Changes since 6.06
        ------------------

  o Small bugfix for 1x1 images

  o Fix for platforms (eg Win32) where char is signed by default

  o Win32 and Linux versions now accept sprites


        Desktop use
        -----------

Pretty straightforward. Run !InterGif; drag your sprite file,
Animator file, Draw file, or GIF onto the left-hand bit of the
window; set any options you want in the middle bit of the window;
and save your GIF or sprite file out from the right-hand bit of
the window. The options are:

  o Interlaced
        Produce an interlaced GIF: in other words, one which a Web
    browser can render quickly at a low resolution, filling in the
    details later as they arrive.

  o Looping animation
        Normally an animated GIF plays through once and stops. If
    you tick this option, you'll get an animated GIF that plays
    over and over again. This is a Netscape extension to the GIF
    format, but hopefully it will become a popular one -- both
    MSIE and Fresco now support it too.

  o Join input files
        This option causes InterGif to look for only one frame in
    the file you give it, and then look for the next frame in
    another file with the numeric part of the file incremented.
    For instance, you could have three files called frame000,
    frame001, and frame002 and create an three-frame animation by
    dragging frame000 (only) onto the InterGif window and
    choosing "Join input files".

  o Set delay
        This lets you set the frame rate, in centiseconds. This
    overrides any frame rate specified in the input file.
        If this is *not* ticked, InterGif's output uses the
    same frame rate as its input. You can change frame delays
    individually in Animator files in the usual way (in Animator,
    press F7) or in sprite files by giving the frames sprite
    names with "delay" in them: for instance, a sprite called
    "037delay25" will be given a delay of 25 centiseconds.
    (Anything before the word "delay" is ignored.)
        If you leave "Set delay" unticked, and the input file
    doesn't specify frame delays, a default of 8 centiseconds per
    frame (12.5 frames per second) is used.
        Note that you can't have different delays for different
    frames if you tick "Set delay"; if you want that, you have to
    set it up in your sprite or Animator file.

  o Transparency
        Choose None to get a wholly opaque GIF (no masking), Auto
    to get InterGif to use the sprites' masks (or the film's
    background colour); or you can specify a transparent
    pixel-value directly.
        (Hint: to find out what pixel-value a sprite pixel has,
    load the sprite into Paint, ensure its palette window is
    showing, click Menu over the pixel you want, and choose
    "Paint->Select colour".)

  o Trim
        This option causes InterGif to remove wholly transparent
    rows and columns from the edges of the image. This means that
    the output image may be a different size from the input one,
    which is otherwise never the case.
        This option ticks itself automatically if you're making a
    transparent, interlaced GIF: for the reason why, see the
    section "Netscape Communicator" below.
        You probably want to tick this if you're converting a
    Draw file, as these often end up with one or two transparent
    rows and columns at the edges.

  o Split output
        This splits up the input file into one output file per
    frame. Not, I admit, terribly useful, unless you need to
    import something into an application that expects lots of
    one-frame GIFs -- for instance, Sun's Java Animator applet.
    The names of the files are taken from the one you give, with
    any numeric part incremented as needed, so if you save a
    three-frame animation as frame001/gif, you also get
    frame002/gif and frame003/gif.

  o Web site
        Clicking on this button takes you to my Web pages on
    chaos, as described above. For this to work, you need to be
    connected to the Internet, and also have a Web browser loaded
    which understands ANT's URL broadcast message -- for example,
    Fresco or ArcWeb. (Probably the others too, these days.)

  o Palette...
        This icon opens the Palette Options window, giving you
    the following further options:

      o Use existing
            This does the same as previous versions of InterGif:
        it discards palette entries that aren't actually used,
        but keeps all the others.

      o Acorn standard 256
      o 216 cube
            These map all colours in the input onto the nearest
        ones in either the standard Acorn 256-colour "mode 15"
        palette, or the Macintosh/PC standard 216-entry colour
        cube. This is useful, for instance, for reducing the size
        of 256-greyscale images.

      o From file
            You can also map colours to those in any Acorn
        palette file (such as one saved from !Paint).

      o Find best
            This is the most powerful option: selecting this
        makes InterGif calculate the optimal palette for
        displaying the input images, and then map to that. You
        can tell it to calculate any size palette from 2 to 256
        entries. InterGif uses the "median cut" algorithm to
        calculate the palette.

  o ChangeFSI...
        This icon opens the InterGif calling ChangeFSI window,
    which gives you the option of pre-processing InterGif's input
    file with Acorn's ChangeFSI image manipulation
    program. This is mainly useful for importing files in formats
    which InterGif doesn't understand directly: for instance, the
    "Targa" files output by POV-Ray for Windows.
        InterGif can give ChangeFSI any of a large range of
    command-line options: most of the time you probably want this
    set to just
            28
     -- which tells ChangeFSI to convert things to 256-colour
    sprites. For details of the other options you can apply, see
    the "FSIuse" text file inside the !ChangeFSI directory.
        If the icons in this window are greyed out, this means
    <ChangeFSI$Dir> isn't set: you should make sure !ChangeFSI
    has been seen by the filer. If you don't have ChangeFSI at
    all, or if you've got a version older than 1.12, you can get
    1.12 from Acorn's FTP site at ftp://ftp.acorn.com/ .
        There's a whole section on ChangeFSI later on in this
    Help file.


        Command-line use
        ----------------

The !Boot file of !InterGif sets up Alias$intergif, so you no
longer need to copy the intergif file into your library
directory.
    At its simplest, you can just type intergif and the name of
your sprite or film file, and it'll be converted. Here's a full
list of the options:

intergif [-i] [-loop] [-s ] [-split] [-d cs] [-t [pixel]] [-trim] [-join]
         [-216 | -256 | -pal palfile | -best n ] [-c cfsi-options]
         [-o outfile] infile

    -i
        Produce an interlaced GIF
    -loop
        Looping animation
    -s
        Produce a sprite rather than a GIF
    -join
        Join several input files
    -split
        One frame per file
    -d cs
        Frame delay in centiseconds
    -t
        Use automatic transparency (default is no transparency)
    -t pixel
        Use specified pixel as transparent
    -trim
        Remove any transparent border
    -216
        Map to Macintosh/PC colour-cube palette
    -256
        Map to Acorn mode 15 palette
    -pal palfile
        Map to given palette
    -best n
        Find best n-colour palette and map to that (2<=n<=256)
    -o outfile
        Filename for the output (default is <infile>/gif)
    -c cfsi-options
        Preprocess using ChangeFSI with the given options (see below)
    infile
        A RiscOS sprite, Draw, Complete Animator or GIF file


        Size is important
        -----------------

Since at least version 2.02, InterGif has optimised out any
wholly transparent rows and columns at the edges of the first (or
only) frame of transparent GIFs. It does this by setting the size
in the Logical Screen Descriptor to the size of the whole GIF,
and the size in the first Frame Descriptor to the smaller
rectangle which bounds the first frame. This is all completely as
per GIF spec, and is what happens for the second and subsequent
frames of animated GIFs anyway.
    However, some programs which read GIFs (usually those which
either don't understand animations, or don't understand
transparency) incorrectly ignore the LSD size and use the FD
size. These programs include ChangeFSI, Claris HomePage, and
early versions of Fresco (before 1.60). This is a problem as it
can lead to Web authors specifying the wrong WIDTH= and HEIGHT=
attributes in Web pages. All versions of Netscape and MSIE use
the LSD size (at least for GIF89's).
    Early versions of the program "Creator" only set the FD size
and not the LSD size; such images look wrong in MSIE. Netscape
cheats! and uses only the FD size for GIF87 images and
(correctly) the LSD size for GIF89 images. As of version 1.63,
this is Fresco's behaviour too.


        Netscape Communicator
        ---------------------

Some interlaced transparent GIFs made with version 6.01 or
earlier of InterGif may look wrong in Netscape Communicator
(Netscape 4): any that do, should be reconverted with version
6.02 or later. You may wish to use the new -trim option; if not,
your GIF will be compressed slightly less well than it could be.
This is due to a bug in Netscape 4, not in InterGif. For grody
technical details, read on.
    Netscape 4, in both the Windows and Solaris versions, gets it
wrong if an interlaced image has a border optimised out on the
first frame (in the manner described in "Size is important"
above). The symptom is that black, non-transparent lines appear
every fourth pixel down "transparent" areas of the image. This is
*unquestionably* a bug in Communicator rather than InterGif
(especially in view of the fact that Netscape 3.02 gets it
right), but, powerless as I am in the face of Netscape
Corporation, I've stopped InterGif from optimising out the border
if an interlaced GIF is being made.
    This means that such GIFs end up being compressed less
optimally than they might. If this is a problem (and it may not
be, as interlaced GIFs usually end up compressed less well than
non-interlaced ones anyway) you can use the new -trim option to
*remove*, rather than just avoid compressing, the transparent
border. When using -trim, InterGif's output will *not* be the
same size in pixels as the input image (it is in all other
cases). You can use the HSPACE= and VSPACE= attributes of the
HTML <IMG> tag to produce a transparent border around a trimmed
image.


        Using ChangeFSI with InterGif
        -----------------------------

Some very powerful results are possible using this option. You
need to read the help file "FSIuse" inside the !ChangeFSI
directory, to know what to put in the InterGif's ChangeFSI
Options icon (or pass with the -c command-line option).

  * Versions of ChangeFSI

There are several different versions of ChangeFSI circulating.
The one available on Acorn's FTP site is, at time of writing,
version 1.12, but there are later versions: I think these were
distributed with RiscOS 3.6 and 3.7. The version I've got calls
itself 1.13S, and I can't remember where I got it.
    The only problem that older versions cause to InterGif, is
that some early versions set ChangeFSI$Dir in their !Run files
but not in their !Boot files, so InterGif won't know where to
find the ChangeFSI program until ChangeFSI has already been run
once. Version 1.12 fixes this.
    In some versions of ChangeFSI, the FSIuse help file mentioned
above is in !ChangeFSI.Documents rather than !ChangeFSI itself.

  * ChangeFSI only knows about single-frame files

This means that if you wish to run ChangeFSI on an animation file
-- if, for instance, you've got an animated GIF you want to
reduce in size -- you have to use InterGif twice.
    The first time, you need to have the "Split output files" or
-split option set: InterGif will produce a whole series of
one-frame sprite files.
    You then need to feed these sprite files back into InterGif,
this time with Join input files or -join selected (plus your
ChangeFSI options to reduce size or whatever): this will produce
the reduced-size animation file you wanted.

  * ChangeFSI doesn't know about masking or transparency

ChangeFSI treats all input files as having a completely solid
mask (no transparency). There isn't really a good workaround for
this, as ChangeFSI can't know what background colour to fade
"half-lit" edge pixels against.
    All you can really do is edit your animation afterwards, in
Paint or The Complete Animator, to re-supply the transparency by
hand.

  * Example ChangeFSI settings

If all you're doing is using ChangeFSI to cope with an input
format that InterGif doesn't understand itself, you just need to
click on the ChangeFSI... button to open the "InterGif calling
ChangeFSI" window, tick the tickbox, and enter
        28
in the Options icon. The "28" tells ChangeFSI to convert things
to 256-colour sprites. The command-line equivalent would be
something like
        intergif in/bmp -o out/gif -c "28"

To reduce the input file to half-size, enter
        28 1:2 1:2
or use a command like
        intergif in -o out -c "28 1:2 1:2"

If you've got a "deep" (16bpp or 24bpp) input image, you can use
ChangeFSI to convert it to a deep sprite, and then tell InterGif
to choose the optimal 256-colour palette, by entering
        S32,90,90
and then choosing Find best in the "InterGif palette options"
window; or, from the command line,
        intergif in -o out -c "S32,90,90" -best 256
Older versions of ChangeFSI won't understand the S32,90,90 option
though, and you may get an error.

My favourite one is converting a whole directory of output files
from POV-Ray for Windows (in 24bpp Targa format) into a
reduced-size animated GIF in one operation:
        intergif frame000/tga -o anim/gif -join -c "28 1:3 1:3"


        See also
        --------

    The InterGif page
        http://utter.chaos.org.uk/~pdh/software/intergif.htm
    The AADraw page
        http://utter.chaos.org.uk/~pdh/software/aadraw.htm
    The Complete Animator
        http://www.iota.co.uk/animator/
    GIF89a specification
        http://asterix.seas.upenn.edu/~mayer/lzw_gif/gif89a.html


                                                 [e-mail]
                                              19th February, 1998