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[project @ 2004-05-31 19:56:38 by rjw]

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Improved Tinct and documentation.

svn path=/import/netsurf/; revision=902
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Richard Wilson 2004-05-31 19:56:38 +00:00
parent 58bca93f8c
commit a6fa745ed9
2 changed files with 86 additions and 32 deletions
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Tinct
=====
The ability to plot alpha-blended sprites is only provided by certain
versions of RISC OS provided by RISC OS Ltd (ie RISC OS Select), and
currently not by the latest versions provided by Castle (ie RISC OS 5)
There is currently no separate module available from RISC OS Ltd, nor a
version of Select that will function on an Iyonix. As such, users of machines
that will not run RISC OS 4 (and thus Select) cannot display images with
variable transparency (eg PNGs).
This module provides the necessary functionality to display alpha-blended
This module provides the necessary functionality to display alpha-blended
sprites both scaled and otherwise. It also provides functions for dithering
and performing bi-linear filtering to improve their appearance.
Technical information
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
To ensure future compatibilty, this module does not patch the OS in any way
To ensure future compatibility, this module does not patch the OS in any way
and works in a totally legal way. It also does not write to itself in any
way, so is suitable for running from ROM.
Redirection to sprites is supported, although due to the overheads involved
with caching the colour translation tables it is not recommended that this is
done. There are some exceptions to this, however, as output to a 32bpp mode
does not cause the tables to be re-calculated, and redirecting to a sprite
that has the same characteristics as the current mode and palette has a
minimal overhead.
Tinct comes in two different variants - one that is slightly faster and
only suitable for memory architectures that support LDRH and STRH (denoted by
a '_h' filename suffix), and one that is suitable for all machines (denoted
by a '_b' filename suffix).
done frequently. There are some exceptions to this, however, as redirecting to
a 16bpp or 32bpp mode sprite does not require any translation tables, and
redirecting to a sprite that has the same mode and palette as the previous
destination that Tinct was used for causes a minimum overhead as the
translation tables are checked and cached values are used if possible.
Format of a sprite with 8-bit alpha channel
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
The sprite format used by Tinct differs from those used by RISC OS Select,
and no facilities to manipulate or create the required format is provided.
All sprites used by Tinct must be 32bpp, and cannot have a mask.
The basic format of the sprite is shown below, with the restrictions to the
standard sprite format marked with an asterisk (*):
and whilst facilities are supplied to convert sprites into the required format,
no facilities are provided to manipulate them.
All sprites used by Tinct must be 32bpp, and cannot have a standard RISC OS
mask specified. The basic format of the sprite is shown below, with the
restrictions to the standard sprite format marked with an asterisk (*):
[+0] Offset to next sprite
[+4] Sprite name, up to 12 characters with trailing zeroes
[+16] Width in words - 1
[+20] Height in scan lines - 1
[+24] * First bit used (must be 0)
[+28] * Last bit used (must be 31)
[+24] First bit used
[+28] Last bit used
[+32] Offset to sprite image
[+36] * Offset to sprite image (no mask allowed)
[+40] * Sprite type (must be &301680B5)
[+40] * Sprite type (must be 0x301680B5)
Whereas for normal sprites the sprite image would be a series of colour words
of the format RrGgBb00, alpha-blended sprites use the empty byte to specify
@ -56,6 +46,14 @@ totally opaque. It should be noted that as a standard 32bpp sprite (eg as
created with !Paint) will have the alpha channel set to 0x00 by default no
output will be visible when plotting as an alpha-blended sprite.
Error handling
¨¨¨¨¨¨¨¨¨¨¨¨¨¨
If an incorrect sprite is attempted to be used, Tinct currently always returns
error number 0x700 (SBadSpriteFile) rather than the specific cause of the
problem (eg. BadDPI, BadMSFlags or BadPixelDepth) as OS_SpriteOp would do.
There are several technical reasons for this behaviour, and future versions of
Tinct may return different error numbers.
SWIs provided
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@ -66,7 +64,9 @@ current OS clipping rectangle is used.
bit 9 of the reason code set. To plot a sprite by name, the sprite should
first be found by using OS_SpriteOp with reason code 0x18 and using the
returned sprite address.
The only error returned by the SWIs is 0x71e (Unrecognised sprite data) that
comes from supplying Tinct with a sprite that does not fit the required
characteristics as specified earlier.
Tinct_PlotAlpha (0x57240)
¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
@ -118,23 +118,77 @@ Tinct_ConvertSprite (0x57244)
¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
Converts a paletted sprite into its 32bpp equivalent. Sufficient memory must
have previously been allocated for the sprite (44 + width * height * 4).
As sprites with 16bpp or 32bpp do not have palettes, conversion cannot be
performed on these variants. All sprites must be supplied with a full palette,
eg 8bpp must have 256 palette entries.
-> R2 Source sprite pointer
R3 Destination sprite pointer
Tinct_AvailableFeatures (0x57245)
¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
Returns the features available to the caller by specifying bits in the flag
word. The features available are unique for each mode, although the current
version of Tinct supports the same subset of features for all modes.
-> R0 Feature to test for, or 0 for all features
<- R0 Features available
Flag word
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All the SWIs provided by Tinct for plotting use a common flag word to
describe the manner in which the plot is performed. Each bit controls a
particular characteristic of the plotting:
0 Forcably read the screen base (only use if hardware scrolling)
0 Forcibly read the screen base (only use if hardware scrolling)
1 Use bi-linear filtering when scaling sprites
2 Dither colours in 16bpp and below
3 Invert dither pattern
4+ Reserved (must be 0)
3 Invert dither pattern
4 Horizontally fill the current graphics window with the sprite
5 Vertically fill the current graphics window with the sprite
6+ Reserved (must be 0)
If a bit is set in the flag word that cannot be honoured by the current
version of Tinct then it is ignored. Tinct_AvailableFeatures can be used
to test in advance what flags will be honoured.
Bilinear filtering
¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
Although bi-linear filtering is only relevant during scaled plotting, this
situation occurs when the EigFactors of the mode are not equal. As such, an
application should always set their preferred flags to ensure consistency.
application should always set their preferred flags to ensure consistency.
Sprite filling
¨¨¨¨¨¨¨¨¨¨¨¨¨¨
If filling is specified, then the supplied co-ordinate is the offset of the
pattern relative to (0, 0) used for the fill. For example, a 64x64 sprite that
is plotted with bits 4 and 5 set and a position of (32, 16) would fill the
current graphics window with multiple copies of the image stating with the
first image plotted at (-32, -48).
Contact details
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If you would like to report a problem relating to Tinct, provide feedback, or
request a licence for a commercial product, please use the details below:
Address: 5 Queens Close, East Markham, Newark, Nottinghamshire, NG22 0QY. UK
E-mail: info@tinct.net
Website: www.tinct.net
Copyright and licence details
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Tinct is © copyright Richard Wilson, 2004.
Distribution and usage
¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨
Unrestricted use of Tinct is hereby granted for any non-commercial product. Any
use as part of a commercial product requires written consent from the author.
No charge may be made relating to the distribution of this software, and this
file should be included in all copies of the software.
Modified versions of this program may not be distributed without the authors
consent, nor may modified versions of the source code or relating files.