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EnigmA Amiga Run 1998 July
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EnigmA AMIGA RUN 29 (1998)(G.R. Edizioni)(IT)[!][issue 1998-07 & 08].iso
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aksvg_dt.lha
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FormatSpecs
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1997-01-03
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================================
= The SVG Graphics File Format = - Version 1, draft version: 03.01.1997
================================
File Format Information
~~~~~~~~~~~~~~~~~~~~~~~
Pictures in the "SVG Graphics File Format" consist of two parts:
a header and an attached xpk-packed or unpacked data file.
Both parts are put into one single file.
Construction (all fields in Motorola BYTE order):
0x00 ID UBYTE[18] "SVG Graphics File" + 0-Byte
0x12 Version UWORD always 1 yet
0x14 GfxDataOffset ULONG header length (depends on version)
0x18 LeftEdge ULONG as with e.g. ILBM
0x1c TopEdge ULONG ...
0x20 Width ULONG ...
0x24 Height ULONG ...
0x28 ColorDepth ULONG used colors as x of 2^x
0x3c ViewMode32 ULONG 32 Bit Amiga ViewMode
0x40 PixelBits UBYTE 1, 8, 24 (future: 16, 32)
0x41 PixelPlanes UBYTE # of planes with PixelBits
0x42 BytesPerLine ULONG bpl of a PixelPlane
0x46 ColorMap UBYTE [256][3] unused, if > 256 Colors (zero-ed)
After that either follows XPK compressed data or uncompressed
data, which can be detected by the leading chars "XPK" or "PP20"
for packed data at GfxDataOffset (relative to beginning of the file).
Please note, that with upto 256 colors (Colordepth <= 8) it has
to be checked, whether the graphics actually is EHB or HAM.
Use the Viewmode32 field for these assumptions when reading, and
maybe OR with HAM_KEY or EHB_KEY when saving.
Note:
-----
"Pixelbits" and Planes do allow a lot of combinations.
Actually used and supported by current software are only the
following:
Bits Planes Depth Content
---------------------------------------------------------------------
1 1..8 1..8 (unaligned Bitmaps with 2..256 colors)
8 1 1..8 (chunky Bitmaps with 2..256 colors)
24 1 24 (24 Bit RGB Bitmaps with 8:8:8 RGB)
So 24 Bit Data should not be saved planewise, but as 24 Bit RGB instead.
If you ever should save any other data, please avoid any planar
configurations and respect the following rules for RGB data chunks:
Bits Planes Depth Content
---------------------------------------------------------------------
16 1 15/16 (15/16 Bit Bitmap with 5:5:5:1 RGB0/A)
32 1 24/32 (24/32 Bit RGB Bitmaps with 8:8:8:8 RGB0/A)
48 1 48 (48 Bit RGB Bitmaps with 16:16:16 RGB)
64 1 48/64 (48/64 Bit RGB Bitmaps with 16:16:16:16 RGB0/A)
... etc ...
Note, that an alpha channel can only be correctly identified, when
"ColorDepth" is handled as an indicator, whether there actually is one,
or not. Programs not supporting alpha channels should simply ignore
the color depth and interpret "Bits=16 and Planes=1" as 5:5:5:0 RGB
and "Bits=32 and Planes=1" as 8:8:8:0 RGB and so on...
Planar configuration actually only was thought for support of 2..256 color
Bitmap contents. We all new, that actually 24 or more bitplanes are
nearly unuseable and actually ugly to handle.
So please respect the "Planes" variable only being valid for values
between 1..8 and only, if "Bits=1" has been set, also note, that
with "Planes=1..8" you must set "ColorDepth=Planes", since other
than with 8 Bit chunky there is no support of unused planes.