Re: Indexed 16 colour palette simulation?
Posted: Sat Jul 07, 2018 11:55 am
Dude, I have to thank you. I got what I wanted in the end, with this video tutorial to get my head around what's going on, your example for some guidance, and my own programming experience.Stifu wrote: ↑Sun Jul 01, 2018 11:41 am We have color swaps in our game, and I think that's pretty much the same idea. We use shaders for that.
Our color swap definitions are here: https://github.com/thomasgoldstein/zabu ... haders.lua
I'm using the latest Love 11, so my colour rgb components are from 0 to 1, instead of 0 to 255, and I just use a source image to load the colour palette from (by getting the colour vaules from a row of pixels) rather than work out how to type them directly.
Here's the result - something that behaves pretty much like Pico 8, with it's fixed palette (I love that palette) and just simple commands to replace any of those colours with one of the others - using a 'base palette' which is never modified (to copy colours from) and a 'live palette' which is the one you modify.
The way you use it is to only create sprites that use the colours from Pico 8's palette (easy with Aseprite, you just load the built in Pico 8 palette), and the palette.png is a row of pixel colours, I've attached the sample project for anyone to unpack. (It includes a little chiptune song I made
)Basically you are a cowboy, and one of the enemies is identical to you but his hat is yellow, and his friend is drawn after and still identical to you, to demonstrate modifying the palette mid-draw to colourise individual sprites. Simply with pal(10,11), which swaps orange for yellow.
Below is the key parts - the shader that refers to the palettes, creating the palette, and using the pal functions to adjust the colours of the sprites (this code won't run on it's own, it's just for an overview).
Code: Select all
local shader_code = [[
extern vec4[16] base_palette;
extern vec4[16] live_palette;
vec4 effect(vec4 colour, Image image, vec2 uvs, vec2 screen_coords) {
vec4 pixel = Texel(image, uvs);
for(int i = 0; i < 16; i++){
vec4 colour = base_palette[i];
if(pixel == colour)
return live_palette[i];
}
return pixel;
}
]]
function love.load()
--SHADER STUFF
--load Pico8 style palette for shader
local palette_img = love.image.newImageData('assets/palette.png')
for x = 1, palette_img:getWidth() do
local r,g,b,a = palette_img:getPixel(x - 1, 0)
base_palette[#base_palette + 1] = {r,g,b,a}
end
live_palette = {unpack(base_palette)}--quick way to copy table
shader = love.graphics.newShader(shader_code)
shader:send("base_palette", unpack(base_palette))
shader:send("live_palette", unpack(live_palette))
end
function love.draw(dt)
--START LOW RES
push:start()
--set the 16 colour palette shader
love.graphics.setShader(shader)
--Draw some text in the low res window
love.graphics.print("Hello World", 0, 0)
love.graphics.print("Again-------", 0, 48)
--Draw a sprite in the low res window
love.graphics.draw(player.img, player.x, player.y)
--affect the palette of one enemy
pal(10,11)
love.graphics.draw(enemy.img, enemy.x, enemy.y)
pal_reset()
love.graphics.draw(enemy2.img, enemy2.x, enemy2.y)
--Clear the shader
love.graphics.setShader()
--end the low res stuff, reset to desktop res
push:finish()
--END LOW RES
end
--source: index to change
--destination: index of colour to change it to
--[[ Uses the base pallete to get colours, so you don't
have to worry about the destination colour being
different than you expect]]
function pal(s,d)
live_palette[s] = base_palette[d]
shader:send("live_palette", unpack(live_palette))
end
--quick version of above, doesn't send the whole array every time.
--Use when making a number of changes, then finish with pal_update()
function pal_q(s,d)
live_palette[s] = base_palette[d]
end
function pal_update()
shader:send("live_palette", unpack(live_palette))
end
--resets pallete to default
function pal_reset()
for i=1,#base_palette do
live_palette[i]=base_palette[i]
end
shader:send("live_palette", unpack(live_palette))
end
--sets entire palette to the one colour, good for flashing a sprite when hit
function pal_flood(d)
for i=1,#base_palette do
live_palette[i]=base_palette[d]
end
shader:send("live_palette", unpack(live_palette))
end