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__________________
Creator user guide
__________________
User, please note
=================
Creator is Shareware. It is not free software. You may freely use this
program for a single 30 day trial period. After this trial period, you must
decide whether or not you want to continue to use the program. If you don't,
you must stop using the program and delete your copy. If you do, you must
register your copy of the program with the author, paying a small
registration fee. Refer to 'Registering' for details.
Please respect the rules of Shareware. Shareware programs like Creator have
cost an awful lot of time and effort to build, will serve you well, and will
cost you very little. If you register the Shareware you use, you will ensure
that Shareware authors will continue to improve the software you use, and
write exciting new Shareware software. If you don't register the Shareware
you use, you are stealing money from Shareware authors, and they will stop
writing Shareware, and start writing much more expensive commercial software
instead.
Copyright notice
================
The copyright (c) of this program belongs to John Kortink. All rights are
reserved.
You may not change this program (except for documented configuration
changes). You may not use any part of this program in any other program or
product without my written approval. You may spread this program freely, but
only in complete and unchanged form, and only against bare distribution costs
(if any). This program is provided 'as is'. No fitness of this program for
any particular purpose is implied. Using this program is entirely at your own
risk.
//
//
// Introduction
//
//
Creator is a pixel image format convertor. It can perform direct conversions
between a wide variety of image formats and image subformats. It can also
change the number of colours in an image. Creator employs sophisticated
algorithms to ensure high quality results.
In addition to this, you will find Creator to be *fast*. In fact, most of
Creator has been written in ARM assembly code, the rest has been written in
C++. In addition, some ported C code is used for JPEG and PNG conversion.
Creator runs under RISC OS 3.1 or later, and supports all relevant Acorn
machines, up to and including the latest RISC PC models. Enhanced functions
provided by the operating system and the hardware are used when available.
//
//
// Using Creator
//
//
On Creator's iconbar menu the usual 'Info' and 'Quit' icons can be found. In
addition, 'Options...' gives access to the 'Options' window and 'Status'
gives access to the 'Status' menu. Both the 'Options' window and the 'Status'
menu are described below.
//
//
// Converting an image
//
//
Drag the image file to Creator's icon. Creator will complain if it cannot
recognize the image format.
The 'Convert image' window will appear, containing the relevant details of
the input image and enabling you to specify the output image details. The
'Convert image' window is described below.
//
//
// The 'Convert image' window
//
//
In this window, you will find two parts, called 'Input image' and 'Output
image'.
The 'Input image' part refers to the image file you dragged to Creator, and
shows details of the input image.
The 'Output image' part refers to the image file you are going to save, and
allows you to specify the format of the output image.
The format of the output image may be chosen as follows :
- 'Format' allows you to choose the image format.
- 'Colours' allows you to choose the number of bits per pixel (bpp) to be
used, which directly relates to the overall maximum number of colours to
be retained (being 2^bpp). If the writable field is not shaded, you may
specify a more precise maximum number of colours if you wish.
- 'Compression' allows you to choose the compression method used.
- 'Filename' allows you to specify the leafname of the image to be saved.
The 'Colours' field deserves some further explanation. This is displayed as
'x bit r:g:b type', where 'x' is the number of bits per pixel (referred to
below as 'bpp'), 'r', 'g', and 'b' are the number of bits of accuracy in a
pixel colour of red, green, and blue respectively, and 'type' is the pixel
colour type. There are essentially two pixel colour types :
- The 'palette' or 'grey' type indicates that pixel values are not pixel
colours themselves but indices into a pixel colour lookup table (called a
'palette'). The 'grey' pixel type also indicates that all palette colours
are greys. If 'fixed' appears in the type, the palette is always fixed.
- The 'true' pixel type indicates that pixel values directly represent pixel
colours. Therefore, 'x' is always the addition of 'r', 'g' and 'b'.
Saving the image may or may not need colour quantization, colour dithering
and/or colour remapping algorithms to be applied. Creator applies the
required algorithms automatically. The accuracy of the calculations performed
by the algorithms may be changed, if needed. Refer to the discussion of the
'Quantization' and 'Dithering' parts of the 'Options' window.
Colour quantization is used whenever a 'superset' of colours (used in the
input image) needs to be reduced to a smaller 'subset' of colours (to be used
in the output image). The colour quantization algorithm calculates the subset
of colours that best represents the superset of colours. Colour quantization
is only used for palette colour output images. The colour quantization
algorithm used in Creator is known as 'Heckbert median cut'.
Colour dithering is used when the number of colours in the output image is
less than that in the input image, or when any of the number of bits per
r/g/b in the output image colours is less than that in the input image
colours, or when the output palette is fixed. In all these cases, some or all
of the input image colours do not have an exactly matching colour in the
output image, and so, for these colours, the 'closest' output image colours
need to be chosen. For a given pixel, the colour dithering algorithm
'diffuses' the errors made by this approximation to neighboring pixels. This
effectively 'smears out' the approximation errors over the rest of the image,
which makes the errors much less visible to the human eye. The colour
dithering algorithm used in Creator is a 'zizag' variant of the widely known
and used Floyd-Steinberg algorithm.
Colour remapping is used whenever the colour quantization algorithm is used,
and it finds that the number of different colours actually used in the input
image is less than or equal to the number of available output image colours.
In this case, the output image palette simply consists of all actually used
input image colours, and all that is needed is 'remapping' of the input image
colours to their respective output image colours. An exact copy of the input
image results. For example, it is not uncommon to encounter 24 bpp 'true
colour' image files in which only 256 colours (or even less) are actually
used. This can happen if someone, somewhere, sometime, for whatever dim
reason, has 'promoted' an 8 bpp palette colour image to 'true colour'. In
these cases, Creator can exactly recreate the original palette colour image.
Creator does the right thing if the output palette turns out to be all grey
(which usually only happens when the output format requires a fixed grey
palette, e.g. PBMPlus 8 bpp or JPEG 8 bpp). In this situation, the colour
dithering algorithm used is unsuitable if the input image is in colour,
because colours are impossible to approximate well with just grey values,
resulting in a bad quality output image. A special 'grey only' dithering
algorithm is used instead, which gives much better results. The 'Dithering'
setting in the 'Options' window has no effect if this algorithm is used.
After making all your choices, you can save the image by dragging the
filetype icon. This will result in the image being saved to the directory
that the icon was dragged to, using the leafname specified under 'Filename'.
//
//
// The 'Options' window
//
//
In this window, you will find four parts, called 'Load options', 'Save
options', 'Quantization' and 'Dithering'.
The 'Load options' part allows you to specify 'load options' for some image
formats, which influence the way images are loaded. In most cases load
options can be left at their default settings. Refer to 'Supported image
formats (detailed)' for information on specific load options.
The 'Save options' part is similar to the 'Load options' part, except that
these options influence the way that images are saved.
The 'Quantization' part allows you to select the accuracy with which colour
frequencies are determined during colour quantization. A higher number of
bits for 'Red', 'Green' or 'Blue' will increase the accuracy with which the
corresponding colour component is handled. Note however that selecting more
than the default of 5 bits per colour component results in only very marginal
and mostly unnoticable differences in image quality. Also note that selecting
less than 5 bits is not really recommended except for the entertainment value
that the resulting images provide. Also note that the memory requirements for
the quantization tables double with every bit added to the total number of
bits. The default setting of 5 bits per colour component (15 bits total)
requires around 128k of memory for the quantization tables.
The 'Dithering' part allows you to select the accuracy of the colour mapping
tables used during colour dithering. Comments similar to the comments under
'Quantization' apply. The default setting of 5 bits per colour component (15
bits total) requires around 128k of memory for the dithering tables.
//
//
// The 'Status' menu
//
//
In this menu you can manipulate Creator's 'status', which consists of a
number of configuration settings.
- 'Save' will save the current status.
- 'Load' will load the saved status.
- 'Default' will load the default status.
- 'Kill' will remove the saved status.
When Creator starts up it loads the saved status, or the default status if
there is no saved status.
The status consists of the 'Quantization' and 'Dithering' settings. These can
all be found in the 'Options' window.
//
//
// Supported image formats (overview)
//
//
Creator can read the following image formats (in alphabetical order) :
- AIM
- BMP
- CadSoft
- Clear
- Degas
- GIF
- IFF
- ImageIO
- IMG
- Irlam
- JPEG
- MacPaint
- MTV
- PBMPlus
- PCX
- Pineapple
- PNG
- QRT
- Sprite
- TIFF
Creator can write the following image formats (in alphabetical order) :
- BMP
- Clear
- GIF
- ImageIO
- JPEG
- PBMPlus
- PNG
- Sprite
- TIFF
The 'ImageIO' format is a special 'internal' format which is not meant to be
used outside Creator.
For more details about the image formats that Creator supports, see
'Supported image formats (detailed)'.
For some image formats that Creator understands, you may specify a few
special settings to be used when loading or saving an image in that format.
Refer to the discussion of the 'Load options' and 'Save options' parts of the
'Options' window.
//
//
// Supported image formats (detailed)
//
//
Following are brief details of all supported image formats.
Image format interpreters are usually very complete, but may, in some cases,
lack support for some subformats. All image interpreters have at least been
tested successfully on all sample images I could find, and have been verified
as well as possible against documentation available to me. Generally, if
Creator encounters formats or subformats that cannot be recognized or are not
supported, it will give up gracefully and provide an indication of why it has
failed.
AIM
===
- Origin
Acorn machines. !AIM (Archimedes Image Manager) program.
- Colours
8 bpp 8:8:8 grey
- Compression
none
- Recognition
filetype &004
- Miscellaneous
Resolution is always 256 x 256 pixels.
BMP
===
- Origin
IBM compatible machines. Microsoft Windows operating system.
- Colours
1 bpp 8:8:8 palette colour
4 bpp 8:8:8 palette colour
8 bpp 8:8:8 palette colour
24 bpp 8:8:8 true colour
- Compression
none
runlength
- Recognition
filetype &69C
'BM' at offset &0
CadSoft
=======
- Origin
Acorn machines. Millipede Prisma display board.
- Colours
8 bpp 8:8:8 palette colour
- Compression
none
runlength
- Recognition
filetype &69A
'MILLIPEDE' at offset &10
Clear
=====
- Origin
Acorn machines. !Translator program and several hardware vendors' programs.
- Colours
1,2,3,4,5,6,7,8 bpp 8:8:8 palette colour
24 bpp 8:8:8 true colour
- Compression
none
- Recognition
filetype &690
Degas
=====
- Origin
Atari machines. Degas and other programs.
- Colours
1,2,4 bpp 3:3:3 palette colour
- Compression
none
runlength
- Recognition
filetype &691
GIF
===
- Origin
Various machines. Graphics Interchange Format, devised by and copyright of
Compuserve Incorporated.
- Colours
1,2,3,4,5,6,7,8 bpp 8:8:8 palette colour
- Compression
12-bit LZW
- Recognition
filetype &695
'GIF87a' or 'GIF89a' at offset &0
- Miscellaneous
When reading, any GIF89a extensions are skipped and ignored. When writing,
GIF87a format is always used.
- Save options
'Interlace' defines whether or not an interlaced image is saved. 'Interlace
= Yes' will save an interlaced image, 'Interlace = No' won't.
IFF
===
- Origin
Various machines. Interchange Format File, devised by Electronic Arts.
- Colours
1,2,3,4,5,6,7,8 bpp 4:4:4 palette colour
1,2,3,4,5,6,7,8 bpp 8:8:8 palette colour
12 bpp 4:4:4 true colour
24 bpp 8:8:8 true colour
- Compression
none
runlength
- Recognition
filetype &693
'FORM' at offset &0 and 'ILBM' at offset &8
IMG
===
- Origin
Atari and IBM compatible machines. Digital Research GEM programs.
- Colours
1 bpp 8:8:8 grey
- Compression
various methods
- Recognition
filetype &692
Irlam
=====
- Origin
Acorn machines. Irlam video digitiser.
- Colours
24 bpp 8:8:8 grey
- Compression
none
- Recognition
filetype &69B
'Irlam' at offset &0
JPEG
====
- Origin
Various machines. Joint Photographic Expert Group, the actual format is
called JFIF (JPEG File Interchange Format), devised by C-Cube Microsystems.
- Colours
8 bpp 8:8:8 grey
24 bpp 8:8:8 true colour
- Compression
Baseline JPEG
- Recognition
filetype &C85
&FF, &D8 at offset &0
- Load options
'Float DCT = No' uses 'fast' integer DCT (Discrete Cosine Transform) code.
'Float DCT = Yes' uses slightly more accurate but 'slow' floating point DCT
code. In practice, both option settings nearly always result in the same
image quality.
- Save options
'Quality = xx', where xx = 0..100, sets the quality level. 100 is best
quality, lowest compression. 0 is worst quality, highest compression.
'Optimize' switches on/off compression optimization (switching it on
results in somewhat smaller files but also uses more processing time).
'Optimize = Yes' switches on compression optimization. 'Optimize = No'
switches it off.
- Miscellaneous
- Processing code is in C. Acknowledgements :
- Compiled with GCC for RISC OS release 1.0.7, (c) 1996 Nick Burrett.
- Linked with UnixLib 3.7b, maintained by Simon Callan.
- Uses IJG JPEG library 6a (07 Feb 1996), (c) 1991-1996 Thomas G. Lane
I am required to state that 'This work is based in part on the work of
the Independent JPEG Group'.
MacPaint
========
- Origin
Apple MacIntosh machines. MacPaint program.
- Colours
1 bpp 8:8:8 grey
- Compression
runlength
- Recognition
filetype &694
'PNTG' at offset &41
- Miscellaneous
Resolution is always 576 x 720 pixels.
MTV
===
- Origin
Various machines. MTV ray tracer.
- Colours
24 bpp 8:8:8 true colour
- Compression
none
- Recognition
filetype &699
PBMPlus
=======
- Origin
Unix machines. Portable Bit Map set of conversion programs, devised by Jef
Poskanzer.
- Colours
1,2,3,4,5,6,7,8 bpp 8:8:8 grey
24 bpp 8:8:8 true colour
- Compression
none
- Recognition
filetype &69E
'Px' at offset &0, where x = 1,2,3,4,5,6
- Miscellaneous
Cannot save 2..7 bpp 8:8:8 grey.
PCX
===
- Origin
IBM compatible machines. ZSoft PC Paintbrush program.
- Colours
1,2,4,8 bpp 8:8:8 palette colour
- Compression
none
runlength
- Recognition
filetype &697
Pineapple
=========
- Origin
Acorn machines. Pineapple Software video digitiser.
- Colours
16 bpp 5:6:5 true colour
- Compression
none
- Recognition
filetype &696
'FSIfile' at offset &0
- Miscellaneous
Resolution is always 512 x 256 pixels.
PNG
===
- Origin
Various machines. Portable Network Graphics format, initially designed to
impove on and fully replace GIF, since GIF's compression algorithm poses
patent problems since 1995. Forget GIF, use PNG (compresses better too !).
- Colours
1,2,4,8 bpp 8:8:8 palette colour
1,2,4 bpp 8:8:8 grey
8 bpp 8:8:8 grey with optional alpha channel
16 bpp 16:16:16 grey with optional alpha channel
24 bpp 8:8:8 true colour with optional alpha channel
48 bpp 16:16:16 true colour with optional alpha channel
- Compression
Deflate
- Recognition
filetype &B60
137, 80, 78, 71, 13, 10, 26, 10 at offset &0
- Miscellaneous
Reader supports all formats, but :
- 16 bpp 16:16:16 grey is 'stripped' to 8 bpp 8:8:8 grey.
- 48 bpp 16:16:16 true colour is 'stripped' to 24 bpp 8:8:8 true colour.
- Alpha channels and transparency cause pixel colours to be recalculated
against a background colour (black if not specified in PNG file).
- Processing code is in C. Acknowledgements :
- Compiled with GCC for RISC OS release 1.0.7, (c) 1996 Nick Burrett.
- Linked with UnixLib 3.7b, maintained by Simon Callan.
- Uses libpng 1.0 beta 3 0.89, (c) 1995-1996 Guy Eric Schalnat.
- Uses zlib 1.0.4, (c) 1995-1996 Jean-loup Gailly and Mark Adler.
QRT
===
- Origin
Various machines. QRT ray tracer.
- Colours
24 bpp 8:8:8 true colour
- Compression
none
- Recognition
filetype &698
Sprite
======
- Origin
Acorn machines. Acorn defined native image format.
- Colours
1,2,4,8 bpp 4:4:4 palette colour
1,2,4,8 bpp 8:8:8 palette colour
15 bpp 5:5:5 true colour
24 bpp 8:8:8 true colour
- Compression
none
- Recognition
filetype &FF9
- Load options
'Default palette' defines the palette to use when palette colour sprites
without a palette are loaded. If the mapping of the bpp of the input to the
corresponding mode is thought of as 1,2,4,8 bpp --> mode 18,19,20,21, then
'Default palette = WIMP' will use the default WIMP palette for the
appropriate mode, and 'Default palette = Mode' will use the default mode
palette (as after a MODE command outside the desktop).
- Save options
'Sprite type' defines the sprite type to save. It only affects the mode
number saved in the sprite file. 'Sprite type = Default' will save old type
sprites for 4:4:4 palette colour input, else new type sprites. 'Sprite type
= Force old' will always save old type sprites. 'Sprite type = Force new'
will always save new type sprites.
- Miscellaneous
Sprite masks are always ignored. Old type 8 bpp 4:4:4 sprites always have
the standard fixed 256-colour palette and are actually saved without
palette.
TIFF
====
- Origin
Various machines. Tag Image File Format (that's 'Tag', not 'Tagged' as most
people think !), devised by Aldus Corporation and Microsoft Corporation.
- Colours
1,2,4,8 bpp 8:8:8 palette colour
24 bpp 8:8:8 true colour
- Compression
none
packbits
12-bit LZW
- Recognition
filetype &FF0
'II' or 'MM' at offset &0
//
//
// Registering
//
//
Please register this program if it serves you well. I am sacrificing a lot of
my time to help increase the amount of good software available for your Acorn
machine. Registration is cheap and easy.
To register, send 30 Dutch Guilders to :
John Kortink
Nutterbrink 31
7544 WJ Enschede
The Netherlands
As soon as your registration has been received you will be a registered user
of Creator. A floppy disc with the latest version of Creator will be sent to
you free of charge, unless you are easily able to access my www page on the
Internet, in which case you already have immediate access to the very latest
versions. Registration also entitles you to free use of any future versions
of Creator.
NOTE : if you register for any one of my applications Translator, Creator or
GreyEdit, you are automatically registered for all of them.
I can accept any of the following types of payment (in order of preference) :
- Cash. You may send any regular European currency, as long as it is
equivalent to 30 Dutch Guilders and consists of 'large', recent bank notes
only.
- Eurocheque. Please note down your pass number on the back of the cheque or
I will be unable to cash the cheque at the bank.
Please note that I cannot accept any other type of payment, including cheques
that are not Eurocheques. I cannot cash these cheques without paying high
bank charges.
Updates of Creator will be made available by (in order of preference) :
- World Wide Web, on www.inter.nl.net/users/J.Kortink.
- Electronic mail, to kortink@inter.nl.net.
- Snail mail, to : see registration address. Include a DD or HD floppy,
return envelope and one International Reply Coupon (IRC).