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!ChangeFSI/256sprites
This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.
Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.
| Tape/disk: | Home » Personal collection » Acorn hard disk » apps » web |
| Filename: | !ChangeFSI/256sprites |
| Read OK: | ✔ |
| File size: | 122F bytes |
| Load address: | 0000 |
| Exec address: | 0000 |
Duplicates
There are 3 duplicate copies of this file in the archive:
- Personal collection » Acorn ADFS disks » Greaseweazled » adfs_1.6M_Apps2.adf » !ChangeFSI/256sprites
- Personal collection » Acorn hard disk » apps » ImagePrcss » !ChangeFSI/256sprites
- Personal collection » Acorn hard disk » apps » web » !ChangeFSI/256sprites
- Personal collection » Acorn hard disk » zipped_disks » 2000_apps_2 » apps2/!ChangeFSI/256sprites
File contents
256 entry palettes in the RISC OS sprite format
===============================================
Introduction
------------
The RISC OS sprite format provides for pictures with and without palettes in
1, 2 and 4 bits per pixel. For 8 bits per pixel a picture with no palette is
dealt with rationally, but a picture with a palette will end up with 64
(pairs of) palette entries. (The pairs of entries are for the possibly
flashing colours). The reader of the format must know how VIDC1's 16 entry
palette works in 8bit mode and apply the necessary bit reordering.
By stepping gingerly around the sprite operations and using ColourTrans
appropriately, sprites with 256 entry palettes can be created and
displayed on all RISC OS machines. Of course, this ability to create and
process a sprite with (say) 256 grey levels in it does not magically
endow the hardware with the ability to display 256 grey levels! The display
will be as close as possible i.e. 16 grey levels with standard hardware;
unless the machine has been hardware extended (e.g. the PCATS Graphics
Enhancer).
Format of a 256 entry palette sprite
------------------------------------
A 256 entry palette sprite is precisely like a 16 entry palette sprite, save
that there are 256 palette entries, each one consisting of a pair of
"palette entry" words of the form &BBGGRR00 as for ColourTrans. All bits of
the entry are significant.
Creating a 256 entry palette sprite
-----------------------------------
If you use OS_SpriteOp 15 to create a sprite with a palette, the OS will
create a 64 entry palette as before. The best thing to do is to create a
sprite with no palette and then to add 2048 to the following entries:
word 1: offset to next sprite
word 9: offset to sprite image
word 10: offset to sprite image/transparency mask
of the sprite and then to add 2048 to
word 4: offset to first free word
of the sprite area control block.
Then write the 256 double words of palette entries starting at word 12
of the sprite, keeping both items in a pair identical:
SYS"OS_SpriteOp",&10f,ram%,name$,0,X,Y,spritemode
sptr%=ram%+ram%!8
pal%=sptr%+11*4
!(sptr%+8*4)+=2048
!(sptr%+9*4)+=2048
!sptr%+=2048
!(ram%+12)+=2048
FORZ%=0TO255:B%=palette!(Z%<<2)ANDNOT&FF
pal%!(Z%*8)=B%:pal%!(Z%*8+4)=B%
NEXT
Manipulating a 256 entry palette sprite
---------------------------------------
All sprite operations work on the 256 entry palette sprite. One can even
switch output to it and generate 256 grey level output into it (with
appropriate care over the GCOL and TINT values required by the OS). Sprite
areas containing 256 entry palette sprites may be loaded, saved etc.
Testing to see if a sprite is a 256 entry palette sprite
--------------------------------------------------------
After creation, the 256 entry palette sprite behaves just like all the
others, so its important to be able to distinguish it on the occasions when
it is needed (for example, when displaying it on the screen).
A 256 entry palette sprite will have the lowest of words 9 and 10 of the
sprite control block equal to 2048+44 (&82C). (If it is already known that
the sprite has no transparency mask, then one can test only word 9).
Displaying a 256 entry palette sprite
-------------------------------------
The call "ColourTrans_SelectTable" takes a 64 entry palette sprite (and 2, 4
and 16) and returns a pixel translation table as needed for OS_SpriteOp 52.
For a 256 entry sprite, one needs to build a similar pixel translation
table directly. The following code will compute a pixel translation table
for any sprite (which hasn't a transparency mask):
IF sptr%!32=44 THEN
palptr%=0
ELSE
FOR grab%=0 TO 2048-8 STEP 8
paltemp%!(grab%>>1)=sptr%!(grab%+44)
NEXT
palptr%=paltemp%
ENDIF
FORQ%=0TO255:pixtrans%?Q%=Q%:NEXT
IFsptr%!32=44+2048 THEN
FORQ%=0TO255
SYS"ColourTrans_ReturnColourNumber",palptr%!(Q%<<2) TO pixtrans%?Q%
NEXT
ELSE
SYS "ColourTrans_SelectTable",m,palptr%,-1,-1,pixtrans%
ENDIF
spx%=-1:FORQ%=0TO255:IFpixtrans%?Q%<>Q% spx%=pixtrans%
NEXT
spx% is either -1 (if no translation needs to be done - this speeds up
OS_SpriteOp 52 a lot!) or pixtrans%; it is passed to OS_SpriteOp 52 in
register 7.
Conclusion
----------
The ability to store, process and display 256 entry palette sprites
represents a small but useful gain for the RISC OS desktop. Common formats
can be converted to sprites without any loss of information and meaningfully
displayed. (Greater fidelity of display can be had with !ChangeFSI (which
can read and generate 256 entry palette sprites) or !Translator)
It is still a good idea to use the default desktop palette whenever possibl��� 00000000 20 20 20 20 20 20 20 20 20 32 35 36 20 65 6e 74 | 256 ent| 00000010 72 79 20 70 61 6c 65 74 74 65 73 20 69 6e 20 74 |ry palettes in t| 00000020 68 65 20 52 49 53 43 20 4f 53 20 73 70 72 69 74 |he RISC OS sprit| 00000030 65 20 66 6f 72 6d 61 74 0a 20 20 20 20 20 20 20 |e format. | 00000040 20 20 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d | ==============| 00000050 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d 3d |================| * 00000070 3d 0a 0a 49 6e 74 72 6f 64 75 63 74 69 6f 6e 0a |=..Introduction.| 00000080 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0a 0a 54 68 |------------..Th| 00000090 65 20 52 49 53 43 20 4f 53 20 73 70 72 69 74 65 |e RISC OS sprite| 000000a0 20 66 6f 72 6d 61 74 20 70 72 6f 76 69 64 65 73 | format provides| 000000b0 20 66 6f 72 20 70 69 63 74 75 72 65 73 20 77 69 | for pictures wi| 000000c0 74 68 20 61 6e 64 20 77 69 74 68 6f 75 74 20 70 |th and without p| 000000d0 61 6c 65 74 74 65 73 20 69 6e 0a 31 2c 20 32 20 |alettes in.1, 2 | 000000e0 61 6e 64 20 34 20 62 69 74 73 20 70 65 72 20 70 |and 4 bits per p| 000000f0 69 78 65 6c 2e 20 46 6f 72 20 38 20 62 69 74 73 |ixel. For 8 bits| 00000100 20 70 65 72 20 70 69 78 65 6c 20 61 20 70 69 63 | per pixel a pic| 00000110 74 75 72 65 20 77 69 74 68 20 6e 6f 20 70 61 6c |ture with no pal| 00000120 65 74 74 65 20 69 73 0a 64 65 61 6c 74 20 77 69 |ette is.dealt wi| 00000130 74 68 20 72 61 74 69 6f 6e 61 6c 6c 79 2c 20 62 |th rationally, b| 00000140 75 74 20 61 20 70 69 63 74 75 72 65 20 77 69 74 |ut a picture wit| 00000150 68 20 61 20 70 61 6c 65 74 74 65 20 77 69 6c 6c |h a palette will| 00000160 20 65 6e 64 20 75 70 20 77 69 74 68 20 36 34 0a | end up with 64.| 00000170 28 70 61 69 72 73 20 6f 66 29 20 70 61 6c 65 74 |(pairs of) palet| 00000180 74 65 20 65 6e 74 72 69 65 73 2e 20 28 54 68 65 |te entries. (The| 00000190 20 70 61 69 72 73 20 6f 66 20 65 6e 74 72 69 65 | pairs of entrie| 000001a0 73 20 61 72 65 20 66 6f 72 20 74 68 65 20 70 6f |s are for the po| 000001b0 73 73 69 62 6c 79 0a 66 6c 61 73 68 69 6e 67 20 |ssibly.flashing | 000001c0 63 6f 6c 6f 75 72 73 29 2e 20 54 68 65 20 72 65 |colours). The re| 000001d0 61 64 65 72 20 6f 66 20 74 68 65 20 66 6f 72 6d |ader of the form| 000001e0 61 74 20 6d 75 73 74 20 6b 6e 6f 77 20 68 6f 77 |at must know how| 000001f0 20 56 49 44 43 31 27 73 20 31 36 20 65 6e 74 72 | VIDC1's 16 entr| 00000200 79 0a 70 61 6c 65 74 74 65 20 77 6f 72 6b 73 20 |y.palette works | 00000210 69 6e 20 38 62 69 74 20 6d 6f 64 65 20 61 6e 64 |in 8bit mode and| 00000220 20 61 70 70 6c 79 20 74 68 65 20 6e 65 63 65 73 | apply the neces| 00000230 73 61 72 79 20 62 69 74 20 72 65 6f 72 64 65 72 |sary bit reorder| 00000240 69 6e 67 2e 0a 0a 42 79 20 73 74 65 70 70 69 6e |ing...By steppin| 00000250 67 20 67 69 6e 67 65 72 6c 79 20 61 72 6f 75 6e |g gingerly aroun| 00000260 64 20 74 68 65 20 73 70 72 69 74 65 20 6f 70 65 |d the sprite ope| 00000270 72 61 74 69 6f 6e 73 20 61 6e 64 20 75 73 69 6e |rations and usin| 00000280 67 20 43 6f 6c 6f 75 72 54 72 61 6e 73 0a 61 70 |g ColourTrans.ap| 00000290 70 72 6f 70 72 69 61 74 65 6c 79 2c 20 73 70 72 |propriately, spr| 000002a0 69 74 65 73 20 77 69 74 68 20 32 35 36 20 65 6e |ites with 256 en| 000002b0 74 72 79 20 70 61 6c 65 74 74 65 73 20 63 61 6e |try palettes can| 000002c0 20 62 65 20 63 72 65 61 74 65 64 20 61 6e 64 0a | be created and.| 000002d0 64 69 73 70 6c 61 79 65 64 20 6f 6e 20 61 6c 6c |displayed on all| 000002e0 20 52 49 53 43 20 4f 53 20 6d 61 63 68 69 6e 65 | RISC OS machine| 000002f0 73 2e 20 4f 66 20 63 6f 75 72 73 65 2c 20 74 68 |s. Of course, th| 00000300 69 73 20 61 62 69 6c 69 74 79 20 74 6f 20 63 72 |is ability to cr| 00000310 65 61 74 65 20 61 6e 64 0a 70 72 6f 63 65 73 73 |eate and.process| 00000320 20 61 20 73 70 72 69 74 65 20 77 69 74 68 20 28 | a sprite with (| 00000330 73 61 79 29 20 32 35 36 20 67 72 65 79 20 6c 65 |say) 256 grey le| 00000340 76 65 6c 73 20 69 6e 20 69 74 20 64 6f 65 73 20 |vels in it does | 00000350 6e 6f 74 20 6d 61 67 69 63 61 6c 6c 79 0a 65 6e |not magically.en| 00000360 64 6f 77 20 74 68 65 20 68 61 72 64 77 61 72 65 |dow the hardware| 00000370 20 77 69 74 68 20 74 68 65 20 61 62 69 6c 69 74 | with the abilit| 00000380 79 20 74 6f 20 64 69 73 70 6c 61 79 20 32 35 36 |y to display 256| 00000390 20 67 72 65 79 20 6c 65 76 65 6c 73 21 20 54 68 | grey levels! Th| 000003a0 65 20 64 69 73 70 6c 61 79 0a 77 69 6c 6c 20 62 |e display.will b| 000003b0 65 20 61 73 20 63 6c 6f 73 65 20 61 73 20 70 6f |e as close as po| 000003c0 73 73 69 62 6c 65 20 69 2e 65 2e 20 31 36 20 67 |ssible i.e. 16 g| 000003d0 72 65 79 20 6c 65 76 65 6c 73 20 77 69 74 68 20 |rey levels with | 000003e0 73 74 61 6e 64 61 72 64 20 68 61 72 64 77 61 72 |standard hardwar| 000003f0 65 3b 0a 75 6e 6c 65 73 73 20 74 68 65 20 6d 61 |e;.unless the ma| 00000400 63 68 69 6e 65 20 68 61 73 20 62 65 65 6e 20 68 |chine has been h| 00000410 61 72 64 77 61 72 65 20 65 78 74 65 6e 64 65 64 |ardware extended| 00000420 20 28 65 2e 67 2e 20 74 68 65 20 50 43 41 54 53 | (e.g. the PCATS| 00000430 20 47 72 61 70 68 69 63 73 0a 45 6e 68 61 6e 63 | Graphics.Enhanc| 00000440 65 72 29 2e 0a 0a 46 6f 72 6d 61 74 20 6f 66 20 |er)...Format of | 00000450 61 20 32 35 36 20 65 6e 74 72 79 20 70 61 6c 65 |a 256 entry pale| 00000460 74 74 65 20 73 70 72 69 74 65 0a 2d 2d 2d 2d 2d |tte sprite.-----| 00000470 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------| 00000480 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0a |---------------.| 00000490 0a 41 20 32 35 36 20 65 6e 74 72 79 20 70 61 6c |.A 256 entry pal| 000004a0 65 74 74 65 20 73 70 72 69 74 65 20 69 73 20 70 |ette sprite is p| 000004b0 72 65 63 69 73 65 6c 79 20 6c 69 6b 65 20 61 20 |recisely like a | 000004c0 31 36 20 65 6e 74 72 79 20 70 61 6c 65 74 74 65 |16 entry palette| 000004d0 20 73 70 72 69 74 65 2c 20 73 61 76 65 0a 74 68 | sprite, save.th| 000004e0 61 74 20 74 68 65 72 65 20 61 72 65 20 32 35 36 |at there are 256| 000004f0 20 70 61 6c 65 74 74 65 20 65 6e 74 72 69 65 73 | palette entries| 00000500 2c 20 65 61 63 68 20 6f 6e 65 20 63 6f 6e 73 69 |, each one consi| 00000510 73 74 69 6e 67 20 6f 66 20 61 20 70 61 69 72 20 |sting of a pair | 00000520 6f 66 0a 22 70 61 6c 65 74 74 65 20 65 6e 74 72 |of."palette entr| 00000530 79 22 20 77 6f 72 64 73 20 6f 66 20 74 68 65 20 |y" words of the | 00000540 66 6f 72 6d 20 26 42 42 47 47 52 52 30 30 20 61 |form &BBGGRR00 a| 00000550 73 20 66 6f 72 20 43 6f 6c 6f 75 72 54 72 61 6e |s for ColourTran| 00000560 73 2e 20 41 6c 6c 20 62 69 74 73 20 6f 66 0a 74 |s. All bits of.t| 00000570 68 65 20 65 6e 74 72 79 20 61 72 65 20 73 69 67 |he entry are sig| 00000580 6e 69 66 69 63 61 6e 74 2e 0a 0a 43 72 65 61 74 |nificant...Creat| 00000590 69 6e 67 20 61 20 32 35 36 20 65 6e 74 72 79 20 |ing a 256 entry | 000005a0 70 61 6c 65 74 74 65 20 73 70 72 69 74 65 0a 2d |palette sprite.-| 000005b0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------| * 000005d0 2d 2d 0a 0a 49 66 20 79 6f 75 20 75 73 65 20 4f |--..If you use O| 000005e0 53 5f 53 70 72 69 74 65 4f 70 20 31 35 20 74 6f |S_SpriteOp 15 to| 000005f0 20 63 72 65 61 74 65 20 61 20 73 70 72 69 74 65 | create a sprite| 00000600 20 77 69 74 68 20 61 20 70 61 6c 65 74 74 65 2c | with a palette,| 00000610 20 74 68 65 20 4f 53 20 77 69 6c 6c 0a 63 72 65 | the OS will.cre| 00000620 61 74 65 20 61 20 36 34 20 65 6e 74 72 79 20 70 |ate a 64 entry p| 00000630 61 6c 65 74 74 65 20 61 73 20 62 65 66 6f 72 65 |alette as before| 00000640 2e 20 54 68 65 20 62 65 73 74 20 74 68 69 6e 67 |. The best thing| 00000650 20 74 6f 20 64 6f 20 69 73 20 74 6f 20 63 72 65 | to do is to cre| 00000660 61 74 65 20 61 0a 73 70 72 69 74 65 20 77 69 74 |ate a.sprite wit| 00000670 68 20 6e 6f 20 70 61 6c 65 74 74 65 20 61 6e 64 |h no palette and| 00000680 20 74 68 65 6e 20 74 6f 20 61 64 64 20 32 30 34 | then to add 204| 00000690 38 20 74 6f 20 74 68 65 20 66 6f 6c 6c 6f 77 69 |8 to the followi| 000006a0 6e 67 20 65 6e 74 72 69 65 73 3a 0a 0a 77 6f 72 |ng entries:..wor| 000006b0 64 20 31 3a 20 6f 66 66 73 65 74 20 74 6f 20 6e |d 1: offset to n| 000006c0 65 78 74 20 73 70 72 69 74 65 0a 77 6f 72 64 20 |ext sprite.word | 000006d0 39 3a 20 6f 66 66 73 65 74 20 74 6f 20 73 70 72 |9: offset to spr| 000006e0 69 74 65 20 69 6d 61 67 65 0a 77 6f 72 64 20 31 |ite image.word 1| 000006f0 30 3a 20 6f 66 66 73 65 74 20 74 6f 20 73 70 72 |0: offset to spr| 00000700 69 74 65 20 69 6d 61 67 65 2f 74 72 61 6e 73 70 |ite image/transp| 00000710 61 72 65 6e 63 79 20 6d 61 73 6b 0a 0a 6f 66 20 |arency mask..of | 00000720 74 68 65 20 73 70 72 69 74 65 20 61 6e 64 20 74 |the sprite and t| 00000730 68 65 6e 20 74 6f 20 61 64 64 20 32 30 34 38 20 |hen to add 2048 | 00000740 74 6f 0a 0a 77 6f 72 64 20 34 3a 20 6f 66 66 73 |to..word 4: offs| 00000750 65 74 20 74 6f 20 66 69 72 73 74 20 66 72 65 65 |et to first free| 00000760 20 77 6f 72 64 0a 0a 6f 66 20 74 68 65 20 73 70 | word..of the sp| 00000770 72 69 74 65 20 61 72 65 61 20 63 6f 6e 74 72 6f |rite area contro| 00000780 6c 20 62 6c 6f 63 6b 2e 0a 0a 54 68 65 6e 20 77 |l block...Then w| 00000790 72 69 74 65 20 74 68 65 20 32 35 36 20 64 6f 75 |rite the 256 dou| 000007a0 62 6c 65 20 77 6f 72 64 73 20 6f 66 20 70 61 6c |ble words of pal| 000007b0 65 74 74 65 20 65 6e 74 72 69 65 73 20 73 74 61 |ette entries sta| 000007c0 72 74 69 6e 67 20 61 74 20 77 6f 72 64 20 31 32 |rting at word 12| 000007d0 0a 6f 66 20 74 68 65 20 73 70 72 69 74 65 2c 20 |.of the sprite, | 000007e0 6b 65 65 70 69 6e 67 20 62 6f 74 68 20 69 74 65 |keeping both ite| 000007f0 6d 73 20 69 6e 20 61 20 70 61 69 72 20 69 64 65 |ms in a pair ide| 00000800 6e 74 69 63 61 6c 3a 0a 0a 53 59 53 22 4f 53 5f |ntical:..SYS"OS_| 00000810 53 70 72 69 74 65 4f 70 22 2c 26 31 30 66 2c 72 |SpriteOp",&10f,r| 00000820 61 6d 25 2c 6e 61 6d 65 24 2c 30 2c 58 2c 59 2c |am%,name$,0,X,Y,| 00000830 73 70 72 69 74 65 6d 6f 64 65 0a 73 70 74 72 25 |spritemode.sptr%| 00000840 3d 72 61 6d 25 2b 72 61 6d 25 21 38 0a 70 61 6c |=ram%+ram%!8.pal| 00000850 25 3d 73 70 74 72 25 2b 31 31 2a 34 0a 21 28 73 |%=sptr%+11*4.!(s| 00000860 70 74 72 25 2b 38 2a 34 29 2b 3d 32 30 34 38 0a |ptr%+8*4)+=2048.| 00000870 21 28 73 70 74 72 25 2b 39 2a 34 29 2b 3d 32 30 |!(sptr%+9*4)+=20| 00000880 34 38 0a 21 73 70 74 72 25 2b 3d 32 30 34 38 0a |48.!sptr%+=2048.| 00000890 21 28 72 61 6d 25 2b 31 32 29 2b 3d 32 30 34 38 |!(ram%+12)+=2048| 000008a0 0a 46 4f 52 5a 25 3d 30 54 4f 32 35 35 3a 42 25 |.FORZ%=0TO255:B%| 000008b0 3d 70 61 6c 65 74 74 65 21 28 5a 25 3c 3c 32 29 |=palette!(Z%<<2)| 000008c0 41 4e 44 4e 4f 54 26 46 46 0a 20 70 61 6c 25 21 |ANDNOT&FF. pal%!| 000008d0 28 5a 25 2a 38 29 3d 42 25 3a 70 61 6c 25 21 28 |(Z%*8)=B%:pal%!(| 000008e0 5a 25 2a 38 2b 34 29 3d 42 25 0a 4e 45 58 54 0a |Z%*8+4)=B%.NEXT.| 000008f0 0a 4d 61 6e 69 70 75 6c 61 74 69 6e 67 20 61 20 |.Manipulating a | 00000900 32 35 36 20 65 6e 74 72 79 20 70 61 6c 65 74 74 |256 entry palett| 00000910 65 20 73 70 72 69 74 65 0a 2d 2d 2d 2d 2d 2d 2d |e sprite.-------| 00000920 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------| * 00000940 0a 0a 41 6c 6c 20 73 70 72 69 74 65 20 6f 70 65 |..All sprite ope| 00000950 72 61 74 69 6f 6e 73 20 77 6f 72 6b 20 6f 6e 20 |rations work on | 00000960 74 68 65 20 32 35 36 20 65 6e 74 72 79 20 70 61 |the 256 entry pa| 00000970 6c 65 74 74 65 20 73 70 72 69 74 65 2e 20 4f 6e |lette sprite. On| 00000980 65 20 63 61 6e 20 65 76 65 6e 0a 73 77 69 74 63 |e can even.switc| 00000990 68 20 6f 75 74 70 75 74 20 74 6f 20 69 74 20 61 |h output to it a| 000009a0 6e 64 20 67 65 6e 65 72 61 74 65 20 32 35 36 20 |nd generate 256 | 000009b0 67 72 65 79 20 6c 65 76 65 6c 20 6f 75 74 70 75 |grey level outpu| 000009c0 74 20 69 6e 74 6f 20 69 74 20 28 77 69 74 68 0a |t into it (with.| 000009d0 61 70 70 72 6f 70 72 69 61 74 65 20 63 61 72 65 |appropriate care| 000009e0 20 6f 76 65 72 20 74 68 65 20 47 43 4f 4c 20 61 | over the GCOL a| 000009f0 6e 64 20 54 49 4e 54 20 76 61 6c 75 65 73 20 72 |nd TINT values r| 00000a00 65 71 75 69 72 65 64 20 62 79 20 74 68 65 20 4f |equired by the O| 00000a10 53 29 2e 20 53 70 72 69 74 65 0a 61 72 65 61 73 |S). Sprite.areas| 00000a20 20 63 6f 6e 74 61 69 6e 69 6e 67 20 32 35 36 20 | containing 256 | 00000a30 65 6e 74 72 79 20 70 61 6c 65 74 74 65 20 73 70 |entry palette sp| 00000a40 72 69 74 65 73 20 6d 61 79 20 62 65 20 6c 6f 61 |rites may be loa| 00000a50 64 65 64 2c 20 73 61 76 65 64 20 65 74 63 2e 0a |ded, saved etc..| 00000a60 0a 54 65 73 74 69 6e 67 20 74 6f 20 73 65 65 20 |.Testing to see | 00000a70 69 66 20 61 20 73 70 72 69 74 65 20 69 73 20 61 |if a sprite is a| 00000a80 20 32 35 36 20 65 6e 74 72 79 20 70 61 6c 65 74 | 256 entry palet| 00000a90 74 65 20 73 70 72 69 74 65 0a 2d 2d 2d 2d 2d 2d |te sprite.------| 00000aa0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------| * 00000ad0 2d 2d 0a 0a 41 66 74 65 72 20 63 72 65 61 74 69 |--..After creati| 00000ae0 6f 6e 2c 20 74 68 65 20 32 35 36 20 65 6e 74 72 |on, the 256 entr| 00000af0 79 20 70 61 6c 65 74 74 65 20 73 70 72 69 74 65 |y palette sprite| 00000b00 20 62 65 68 61 76 65 73 20 6a 75 73 74 20 6c 69 | behaves just li| 00000b10 6b 65 20 61 6c 6c 20 74 68 65 0a 6f 74 68 65 72 |ke all the.other| 00000b20 73 2c 20 73 6f 20 69 74 73 20 69 6d 70 6f 72 74 |s, so its import| 00000b30 61 6e 74 20 74 6f 20 62 65 20 61 62 6c 65 20 74 |ant to be able t| 00000b40 6f 20 64 69 73 74 69 6e 67 75 69 73 68 20 69 74 |o distinguish it| 00000b50 20 6f 6e 20 74 68 65 20 6f 63 63 61 73 69 6f 6e | on the occasion| 00000b60 73 20 77 68 65 6e 0a 69 74 20 69 73 20 6e 65 65 |s when.it is nee| 00000b70 64 65 64 20 28 66 6f 72 20 65 78 61 6d 70 6c 65 |ded (for example| 00000b80 2c 20 77 68 65 6e 20 64 69 73 70 6c 61 79 69 6e |, when displayin| 00000b90 67 20 69 74 20 6f 6e 20 74 68 65 20 73 63 72 65 |g it on the scre| 00000ba0 65 6e 29 2e 0a 0a 41 20 32 35 36 20 65 6e 74 72 |en)...A 256 entr| 00000bb0 79 20 70 61 6c 65 74 74 65 20 73 70 72 69 74 65 |y palette sprite| 00000bc0 20 77 69 6c 6c 20 68 61 76 65 20 74 68 65 20 6c | will have the l| 00000bd0 6f 77 65 73 74 20 6f 66 20 77 6f 72 64 73 20 39 |owest of words 9| 00000be0 20 61 6e 64 20 31 30 20 6f 66 20 74 68 65 0a 73 | and 10 of the.s| 00000bf0 70 72 69 74 65 20 63 6f 6e 74 72 6f 6c 20 62 6c |prite control bl| 00000c00 6f 63 6b 20 65 71 75 61 6c 20 74 6f 20 32 30 34 |ock equal to 204| 00000c10 38 2b 34 34 20 28 26 38 32 43 29 2e 20 28 49 66 |8+44 (&82C). (If| 00000c20 20 69 74 20 69 73 20 61 6c 72 65 61 64 79 20 6b | it is already k| 00000c30 6e 6f 77 6e 20 74 68 61 74 0a 74 68 65 20 73 70 |nown that.the sp| 00000c40 72 69 74 65 20 68 61 73 20 6e 6f 20 74 72 61 6e |rite has no tran| 00000c50 73 70 61 72 65 6e 63 79 20 6d 61 73 6b 2c 20 74 |sparency mask, t| 00000c60 68 65 6e 20 6f 6e 65 20 63 61 6e 20 74 65 73 74 |hen one can test| 00000c70 20 6f 6e 6c 79 20 77 6f 72 64 20 39 29 2e 0a 0a | only word 9)...| 00000c80 44 69 73 70 6c 61 79 69 6e 67 20 61 20 32 35 36 |Displaying a 256| 00000c90 20 65 6e 74 72 79 20 70 61 6c 65 74 74 65 20 73 | entry palette s| 00000ca0 70 72 69 74 65 0a 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |prite.----------| 00000cb0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------| 00000cc0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0a 0a 54 68 65 |-----------..The| 00000cd0 20 63 61 6c 6c 20 22 43 6f 6c 6f 75 72 54 72 61 | call "ColourTra| 00000ce0 6e 73 5f 53 65 6c 65 63 74 54 61 62 6c 65 22 20 |ns_SelectTable" | 00000cf0 74 61 6b 65 73 20 61 20 36 34 20 65 6e 74 72 79 |takes a 64 entry| 00000d00 20 70 61 6c 65 74 74 65 20 73 70 72 69 74 65 20 | palette sprite | 00000d10 28 61 6e 64 20 32 2c 20 34 0a 61 6e 64 20 31 36 |(and 2, 4.and 16| 00000d20 29 20 61 6e 64 20 72 65 74 75 72 6e 73 20 61 20 |) and returns a | 00000d30 70 69 78 65 6c 20 74 72 61 6e 73 6c 61 74 69 6f |pixel translatio| 00000d40 6e 20 74 61 62 6c 65 20 61 73 20 6e 65 65 64 65 |n table as neede| 00000d50 64 20 66 6f 72 20 4f 53 5f 53 70 72 69 74 65 4f |d for OS_SpriteO| 00000d60 70 20 35 32 2e 0a 46 6f 72 20 61 20 32 35 36 20 |p 52..For a 256 | 00000d70 65 6e 74 72 79 20 73 70 72 69 74 65 2c 20 6f 6e |entry sprite, on| 00000d80 65 20 6e 65 65 64 73 20 74 6f 20 62 75 69 6c 64 |e needs to build| 00000d90 20 61 20 73 69 6d 69 6c 61 72 20 70 69 78 65 6c | a similar pixel| 00000da0 20 74 72 61 6e 73 6c 61 74 69 6f 6e 0a 74 61 62 | translation.tab| 00000db0 6c 65 20 64 69 72 65 63 74 6c 79 2e 20 54 68 65 |le directly. The| 00000dc0 20 66 6f 6c 6c 6f 77 69 6e 67 20 63 6f 64 65 20 | following code | 00000dd0 77 69 6c 6c 20 63 6f 6d 70 75 74 65 20 61 20 70 |will compute a p| 00000de0 69 78 65 6c 20 74 72 61 6e 73 6c 61 74 69 6f 6e |ixel translation| 00000df0 20 74 61 62 6c 65 0a 66 6f 72 20 61 6e 79 20 73 | table.for any s| 00000e00 70 72 69 74 65 20 28 77 68 69 63 68 20 68 61 73 |prite (which has| 00000e10 6e 27 74 20 61 20 74 72 61 6e 73 70 61 72 65 6e |n't a transparen| 00000e20 63 79 20 6d 61 73 6b 29 3a 0a 0a 49 46 20 73 70 |cy mask):..IF sp| 00000e30 74 72 25 21 33 32 3d 34 34 20 54 48 45 4e 0a 20 |tr%!32=44 THEN. | 00000e40 70 61 6c 70 74 72 25 3d 30 0a 45 4c 53 45 0a 20 |palptr%=0.ELSE. | 00000e50 46 4f 52 20 67 72 61 62 25 3d 30 20 54 4f 20 32 |FOR grab%=0 TO 2| 00000e60 30 34 38 2d 38 20 53 54 45 50 20 38 0a 20 20 70 |048-8 STEP 8. p| 00000e70 61 6c 74 65 6d 70 25 21 28 67 72 61 62 25 3e 3e |altemp%!(grab%>>| 00000e80 31 29 3d 73 70 74 72 25 21 28 67 72 61 62 25 2b |1)=sptr%!(grab%+| 00000e90 34 34 29 0a 20 4e 45 58 54 0a 20 70 61 6c 70 74 |44). NEXT. palpt| 00000ea0 72 25 3d 70 61 6c 74 65 6d 70 25 0a 45 4e 44 49 |r%=paltemp%.ENDI| 00000eb0 46 0a 46 4f 52 51 25 3d 30 54 4f 32 35 35 3a 70 |F.FORQ%=0TO255:p| 00000ec0 69 78 74 72 61 6e 73 25 3f 51 25 3d 51 25 3a 4e |ixtrans%?Q%=Q%:N| 00000ed0 45 58 54 0a 49 46 73 70 74 72 25 21 33 32 3d 34 |EXT.IFsptr%!32=4| 00000ee0 34 2b 32 30 34 38 20 54 48 45 4e 0a 20 46 4f 52 |4+2048 THEN. FOR| 00000ef0 51 25 3d 30 54 4f 32 35 35 0a 20 20 53 59 53 22 |Q%=0TO255. SYS"| 00000f00 43 6f 6c 6f 75 72 54 72 61 6e 73 5f 52 65 74 75 |ColourTrans_Retu| 00000f10 72 6e 43 6f 6c 6f 75 72 4e 75 6d 62 65 72 22 2c |rnColourNumber",| 00000f20 70 61 6c 70 74 72 25 21 28 51 25 3c 3c 32 29 20 |palptr%!(Q%<<2) | 00000f30 54 4f 20 70 69 78 74 72 61 6e 73 25 3f 51 25 0a |TO pixtrans%?Q%.| 00000f40 20 4e 45 58 54 0a 45 4c 53 45 0a 20 53 59 53 20 | NEXT.ELSE. SYS | 00000f50 22 43 6f 6c 6f 75 72 54 72 61 6e 73 5f 53 65 6c |"ColourTrans_Sel| 00000f60 65 63 74 54 61 62 6c 65 22 2c 6d 2c 70 61 6c 70 |ectTable",m,palp| 00000f70 74 72 25 2c 2d 31 2c 2d 31 2c 70 69 78 74 72 61 |tr%,-1,-1,pixtra| 00000f80 6e 73 25 0a 45 4e 44 49 46 0a 73 70 78 25 3d 2d |ns%.ENDIF.spx%=-| 00000f90 31 3a 46 4f 52 51 25 3d 30 54 4f 32 35 35 3a 49 |1:FORQ%=0TO255:I| 00000fa0 46 70 69 78 74 72 61 6e 73 25 3f 51 25 3c 3e 51 |Fpixtrans%?Q%<>Q| 00000fb0 25 20 73 70 78 25 3d 70 69 78 74 72 61 6e 73 25 |% spx%=pixtrans%| 00000fc0 0a 4e 45 58 54 0a 0a 73 70 78 25 20 69 73 20 65 |.NEXT..spx% is e| 00000fd0 69 74 68 65 72 20 2d 31 20 28 69 66 20 6e 6f 20 |ither -1 (if no | 00000fe0 74 72 61 6e 73 6c 61 74 69 6f 6e 20 6e 65 65 64 |translation need| 00000ff0 73 20 74 6f 20 62 65 20 64 6f 6e 65 20 2d 20 74 |s to be done - t| 00001000 68 69 73 20 73 70 65 65 64 73 20 75 70 0a 4f 53 |his speeds up.OS| 00001010 5f 53 70 72 69 74 65 4f 70 20 35 32 20 61 20 6c |_SpriteOp 52 a l| 00001020 6f 74 21 29 20 6f 72 20 70 69 78 74 72 61 6e 73 |ot!) or pixtrans| 00001030 25 3b 20 69 74 20 69 73 20 70 61 73 73 65 64 20 |%; it is passed | 00001040 74 6f 20 4f 53 5f 53 70 72 69 74 65 4f 70 20 35 |to OS_SpriteOp 5| 00001050 32 20 69 6e 0a 72 65 67 69 73 74 65 72 20 37 2e |2 in.register 7.| 00001060 0a 0a 43 6f 6e 63 6c 75 73 69 6f 6e 0a 2d 2d 2d |..Conclusion.---| 00001070 2d 2d 2d 2d 2d 2d 2d 0a 0a 54 68 65 20 61 62 69 |-------..The abi| 00001080 6c 69 74 79 20 74 6f 20 73 74 6f 72 65 2c 20 70 |lity to store, p| 00001090 72 6f 63 65 73 73 20 61 6e 64 20 64 69 73 70 6c |rocess and displ| 000010a0 61 79 20 32 35 36 20 65 6e 74 72 79 20 70 61 6c |ay 256 entry pal| 000010b0 65 74 74 65 20 73 70 72 69 74 65 73 0a 72 65 70 |ette sprites.rep| 000010c0 72 65 73 65 6e 74 73 20 61 20 73 6d 61 6c 6c 20 |resents a small | 000010d0 62 75 74 20 75 73 65 66 75 6c 20 67 61 69 6e 20 |but useful gain | 000010e0 66 6f 72 20 74 68 65 20 52 49 53 43 20 4f 53 20 |for the RISC OS | 000010f0 64 65 73 6b 74 6f 70 2e 20 43 6f 6d 6d 6f 6e 20 |desktop. Common | 00001100 66 6f 72 6d 61 74 73 0a 63 61 6e 20 62 65 20 63 |formats.can be c| 00001110 6f 6e 76 65 72 74 65 64 20 74 6f 20 73 70 72 69 |onverted to spri| 00001120 74 65 73 20 77 69 74 68 6f 75 74 20 61 6e 79 20 |tes without any | 00001130 6c 6f 73 73 20 6f 66 20 69 6e 66 6f 72 6d 61 74 |loss of informat| 00001140 69 6f 6e 20 61 6e 64 20 6d 65 61 6e 69 6e 67 66 |ion and meaningf| 00001150 75 6c 6c 79 0a 64 69 73 70 6c 61 79 65 64 2e 20 |ully.displayed. | 00001160 28 47 72 65 61 74 65 72 20 66 69 64 65 6c 69 74 |(Greater fidelit| 00001170 79 20 6f 66 20 64 69 73 70 6c 61 79 20 63 61 6e |y of display can| 00001180 20 62 65 20 68 61 64 20 77 69 74 68 20 21 43 68 | be had with !Ch| 00001190 61 6e 67 65 46 53 49 20 28 77 68 69 63 68 0a 63 |angeFSI (which.c| 000011a0 61 6e 20 72 65 61 64 20 61 6e 64 20 67 65 6e 65 |an read and gene| 000011b0 72 61 74 65 20 32 35 36 20 65 6e 74 72 79 20 70 |rate 256 entry p| 000011c0 61 6c 65 74 74 65 20 73 70 72 69 74 65 73 29 20 |alette sprites) | 000011d0 6f 72 20 21 54 72 61 6e 73 6c 61 74 6f 72 29 0a |or !Translator).| 000011e0 0a 49 74 20 69 73 20 73 74 69 6c 6c 20 61 20 67 |.It is still a g| 000011f0 6f 6f 64 20 69 64 65 61 20 74 6f 20 75 73 65 20 |ood idea to use | 00001200 74 68 65 20 64 65 66 61 75 6c 74 20 64 65 73 6b |the default desk| 00001210 74 6f 70 20 70 61 6c 65 74 74 65 20 77 68 65 6e |top palette when| 00001220 65 76 65 72 20 70 6f 73 73 69 62 6c ff ff ff |ever possibl...| 0000122f
.