103 lines
2.6 KiB
Lua
103 lines
2.6 KiB
Lua
-- Simple error diffusion dithering
|
|
-- TODO use HSV/HSL for dithering closer to human perception
|
|
|
|
local matrices = {
|
|
none = {
|
|
fraction = 0
|
|
},
|
|
floyd_steinberg = {
|
|
fraction = 1/16,
|
|
{x_off = 1, 7};
|
|
{x_off = -1, 3, 5, 1};
|
|
},
|
|
jarvis_judice_ninke = {
|
|
fraction = 1/48,
|
|
{x_off = 1, 7, 5};
|
|
{x_off = -2, 3, 5, 7, 5, 3};
|
|
{x_off = -2, 1, 3, 5, 3, 1};
|
|
},
|
|
stucke = {
|
|
fraction = 1/42,
|
|
{x_off = 1, 8, 4};
|
|
{x_off = -2, 2, 4, 8, 4, 2};
|
|
{x_off = -2, 1, 2, 4, 2, 1};
|
|
},
|
|
atkinson = {
|
|
fraction = 1/8,
|
|
{x_off = 1, 1, 1};
|
|
{x_off = -1, 1, 1, 1 };
|
|
{x_off = 0, 1 };
|
|
},
|
|
burkes = {
|
|
fraction = 1/42,
|
|
{x_off = 1, 8, 4};
|
|
{x_off = -2, 2, 4, 8, 4, 2};
|
|
},
|
|
sierra = {
|
|
fraction = 1/16,
|
|
{x_off = 1, 4, 3};
|
|
{x_off = -2, 1, 2, 3, 2, 1};
|
|
},
|
|
sierra_lite = {
|
|
fraction = 1/4,
|
|
{x_off = 1, 2},
|
|
{x_off = -1, 1, 1 },
|
|
},
|
|
two_row_sierra = {
|
|
fraction = 1/32,
|
|
{x_off = 1, 5, 3},
|
|
{x_off = -2, 2, 4, 5, 4, 2},
|
|
{x_off = -1, 2, 3, 2 },
|
|
},
|
|
}
|
|
texgen.dithering_methods = matrices
|
|
|
|
local clamp = modlib.math.clamp
|
|
return function(method)
|
|
local matrix = assert(matrices[method])
|
|
return function(png, closest_color)
|
|
local width = png.width
|
|
local diffused_errors = {}
|
|
local zero_err = {r = 0, g = 0, b = 0}
|
|
for index, color in ipairs(png.data) do
|
|
local x, y = (index - 1) % width, math.floor((index - 1) / width)
|
|
color = modlib.minetest.colorspec.from_number(color)
|
|
local diff_err = diffused_errors[index] or zero_err
|
|
diffused_errors[index] = nil
|
|
local col_err = {
|
|
r = clamp(color.r + diff_err.r, 0, 255),
|
|
g = clamp(color.g + diff_err.g, 0, 255),
|
|
b = clamp(color.b + diff_err.b, 0, 255)
|
|
}
|
|
local new_color = closest_color(col_err)
|
|
png.data[index] = modlib.minetest.colorspec.new{
|
|
r = new_color.r,
|
|
g = new_color.g,
|
|
b = new_color.b,
|
|
a = color.a -- keep alpha
|
|
}:to_number()
|
|
-- Diffuse error
|
|
local weight = matrix.fraction * color.a / 255
|
|
if weight > 0 then
|
|
local err = {
|
|
r = weight * (new_color.r - col_err.r),
|
|
g = weight * (new_color.g - col_err.g),
|
|
b = weight * (new_color.b - col_err.b)
|
|
}
|
|
for y_off, row in ipairs(matrix) do
|
|
local ey = y + y_off - 1
|
|
for x_off, factor in ipairs(row) do
|
|
local ex = x + row.x_off + x_off - 1
|
|
local idx = ey * width + ex
|
|
local derr = diffused_errors[idx] or {r = 0, g = 0, b = 0}
|
|
derr.r = derr.r + factor * err.r
|
|
derr.g = derr.g + factor * err.g
|
|
derr.b = derr.b + factor * err.b
|
|
diffused_errors[idx] = derr
|
|
end
|
|
end
|
|
end
|
|
end
|
|
end
|
|
end
|