Author Topic: Change a sprite's hue, saturation and brightness  (Read 5925 times)

Offline Wampus

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UPDATE!

The function ShiftColorValue has been improved. The calculations have been optimised and it only does the minimum  work needed to get its result. You can now also saturate and brighten the original sprite more than the original values. All round a better approach. The new routine has been attached to this post.

See my second post below on this thread for an explanation of the ShiftColorValue function

Back to OP:-

---------------------------

Wrote a routine to see how I could use SPRITE2MEM and MEM2SPRITE to create new sprites with different colour schemes. This sort of thing was seen a lot in the 16-bit era. Example screenshot:-



In this demo you can adjust the hue (rainbow bar), the brightness (dark to light bar) and saturation (gray to red bar) of Sagat's flesh, bandages, belt and shorts. Click 'Change' to have a look at the new sprite you've created with your settings and 'Default' to return to default  ;/

Just compile HueShiftExample.gbap to have a look.

[attachment deleted by admin]
« Last Edit: 2011-Jan-29 by Ragaril »

Offline Kitty Hello

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Wow, that's handy!

Offline Albert

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WoW!
Exactly what I need.

Offline Moru

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Nice, just what we were discussing last year :-)

Offline Hark0

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Cool!
 ;)
http://litiopixel.blogspot.com
litiopixel.blogspot.com - Desarrollo videojuegos Indie · Pixel-Art · Retroinformática · Electrónica Development Indie Videogames · Pixel-Art · Retrocomputing · Electronic

Offline Wampus

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Ok, so clear explanation of ShiftColorValue function

newcolor% = ShiftColorValue ( oldcolor%,  brightness%,  saturation%,  hue% )

The variable newcolor is given a value in RGBA calculated from oldcolor according to settings brightness, saturation and hue.

brightness can be given values from 0 to 200. 0 is totally black. 200 is totally white. 100 is normal brightness.

saturation can be given values from 0 to 200. 0 is totally colourless - black & white. 200 is maximum saturation. 100 is normal saturation. Be careful using values above 100. While this can work well much of the time it can produce odd results in some sprites when brightness is over 100.

hue can be given values from 0 to 359. 0 is no change whatsoever. 180 results in the complete opposite colour.

Code: (glbasic) [Select]
FUNCTION ShiftColorValue: color, bri, sat, hue

// color is the original color to change according to the following values:-

// bri = brightness. Can be 0 to 100 to 200. 0 = total darkness. 100 = normal light. over 100 you'll get a bleached look - "over" brightness
// sat = saturation. Can be 0 to 100 to 200. 0 = black & white. 100 = normal saturation. over 100 is "over" saturation. More colourful.
// hue = hue shift. Can be 0 to 359. 0 is no change.

LOCAL hu, cmax%, cmin%, diff, r%, g%, b%, a%, tmin%, tdiff%

a = bAND(ASR(color,24),0xff)

IF a = 0

RETURN color

ELSE

r = bAND(color,0xff)
g = bAND(ASR(color,8),0xff)
b = bAND(ASR(color,16),0xff)

cmax = MAX(b,MAX(r,g))
cmin = MIN(b,MIN(r,g))
diff = cmax-cmin

// hue calculations - hu = hue of color%

IF hue <> 0

IF r > g
IF g > b // 7 Between red and yellow
hu = ((g-b)/diff)*60
ELSEIF b > g
IF b = r
hu = 300 // Pure Magnenta
ELSE
hu = 300 + ((r-b)/diff)*60 // 12 Between Magnenta and Red
ENDIF
ELSE // g = b
hu = 0 // 1 Pure Red
ENDIF

ELSEIF g > b
IF b > r // 9 Between green and cyan
hu = 120 + ((b-r)/diff)*60
ELSEIF r > b // 8 Between yellow and green
IF r = g // Pure Yellow
hu = 60
ELSE
hu = 60 + ((g-r)/diff)*60 // 8 Between yellow and green
ENDIF
ELSE // b = r
hu = 120 // 3 Pure green
ENDIF

ELSE // b > r
IF r > g // 11 Between blue and magnenta
hu = 240 + ((r-g)/diff)*60
ELSEIF g > r
IF g = b // Pure Cyan
hu = 180
ELSE
hu = 180 + ((b-g)/diff)*60 // 10 Between cyan and blue
ENDIF
ELSE // r = g
hu = hu = 240 // 5 Pure blue
ENDIF

ENDIF


// Adjust hue

hue = hue + hu

IF hue >= 360 THEN DEC hue, 360

IF hue > 0 AND hue < 60 // Between red and yellow

r = cmax
b = cmin
g = cmin+(hue*(diff/60))

ELSEIF hue > 60 AND hue < 120 // Between Yellow and green

g = cmax
b = cmin
r = cmax-((hue-60)*(diff/60))

ELSEIF hue > 120 AND hue < 180 // Between green and cyan

g = cmax
r = cmin
b = cmin+((hue-120)*(diff/60))

ELSEIF hue > 180 AND hue < 240 // Between cyan and blue

b = cmax
r = cmin
g = cmax-((hue-180)*(diff/60))

ELSEIF hue > 240 AND hue < 300 // Betweeen blue and magnenta

b = cmax
g = cmin
r = cmin+((hue-240)*(diff/60))

ELSEIF hue > 300 // Between mangenta and red

r = cmax
g = cmin
b = cmax-((hue-300)*(diff/60))

ELSEIF hue = 0 // Pure Red

r = cmax
g = cmin
b = cmin

ELSEIF hue = 60 // Pure Yellow

r = cmax
g = cmax
b = cmin

ELSEIF hue = 120 // Pure Green

r = cmin
g = cmax
b = cmin

ELSEIF hue = 180 // Pure Cyan

r = cmin
g = cmax
b = cmax

ELSEIF hue = 240 // Pure Blue

r = cmin
g = cmin
b = cmax

ELSEIF hue = 300 // Pure magnenta

r = cmax
g = cmin
b = cmax

ENDIF

ENDIF


// Adjust saturation

IF sat <> 100

sat = 100-sat

IF r <> cmax

tmin = r
tdiff = cmax - tmin

r = tmin + tdiff*(sat/100)

ENDIF

IF g <> cmax

tmin = g
tdiff = cmax - tmin

g = tmin + tdiff*(sat/100)

ENDIF

IF b <> cmax

tmin = b
tdiff = cmax - tmin

b = tmin + tdiff*(sat/100)

ENDIF

ENDIF


// Adjust brightness

IF bri <> 100

IF bri = 0

r = 0
g = 0
b = 0

ELSE

DEC r, (100-bri)*2.55

DEC g, (100-bri)*2.55

DEC b, (100-bri)*2.55

ENDIF

ENDIF


IF r < 0 THEN r = 0
IF r > 255 THEN r = 255

IF g < 0 THEN g = 0
IF g > 255 THEN g = 255

IF b < 0 THEN b = 0
IF b > 255 THEN b = 255

RETURN bOR(RGB(r,g,b), ASL(a, 24))

ENDIF

ENDFUNCTION
« Last Edit: 2011-Jan-29 by Ragaril »

Offline Quentin

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Cool thing  :good:

I must admit, I've never used MEM2SPRITE until now. Is it fast enough to be used for ingame sprite manipulation? Or should it be used with care?

Offline Marmor

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its a nice one .  thx

Offline Wampus

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Cool thing  :good:

I must admit, I've never used MEM2SPRITE until now. Is it fast enough to be used for ingame sprite manipulation? Or should it be used with care?

IMO not a good idea to use it on the fly each frame, i.e. in-game. Even if you increased speed by greatly reducing the number of colours you have to work with by keeping them in a pre-calculated list and skipped alpha channel with 0 value it would still be slow even on relatively fast PCs. Its quick, but not that quick.

The kind of practical thing you can do is re-colour a whole set of sprites on a sprite sheet for use later. In this way its not unlike loading a whole new set of sprites (and about as quick). When actually in use they'd work just the same as the original sprites. For example, in a real-time strategy game you could allow the user to make personalised colour changes to their standard set of units before a game starts. Same with a fighting game like the classic 2D versions of Street Fighter games. Another example would be a character creation screen for an RPG. You could allow the user to customise the colour scheme for their player characters in addition to all the other settings.

Offline r0ber7

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Hey Wampus,

Check this out. :)



Muchas gracias!

Note: low framerate is due to Fraps, game runs smoothly. :P

Offline Wampus

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Very nice :)

Incidentally, I'm going to use hue shifting amongst other things to make the appearance of wizards in my Chaos remake easy to change too.