mirror of
https://github.com/sbrl/Minetest-WorldEditAdditions.git
synced 2024-11-23 23:53:44 +01:00
53 lines
1.7 KiB
Lua
53 lines
1.7 KiB
Lua
local wea_c = worldeditadditions_core
|
|
-- Ported from Javascript by Starbeamrainbowlabs
|
|
-- Original source: https://github.com/sidorares/gaussian-convolution-kernel/
|
|
-- From
|
|
-- the code is taken from https://github.com/mattlockyer/iat455/blob/6493c882f1956703133c1bffa1d7ee9a83741cbe/assignment1/assignment/effects/blur-effect-dyn.js
|
|
-- (c) Matt Lockyer, https://github.com/mattlockyer
|
|
|
|
-- hypotenuse has moved to utils/numbers.lua
|
|
|
|
--[[
|
|
* Generates a kernel used for the gaussian blur effect.
|
|
*
|
|
* @param dimension is an odd integer
|
|
* @param sigma is the standard deviation used for our gaussian function.
|
|
*
|
|
* @returns an array with dimension^2 number of numbers, all less than or equal
|
|
* to 1. Represents our gaussian blur kernel.
|
|
]]--
|
|
function worldeditadditions.conv.kernel_gaussian(dimension, sigma)
|
|
if not (dimension % 2) or math.floor(dimension) ~= dimension or dimension < 3 then
|
|
return false, "The dimension must be an odd integer greater than or equal to 3"
|
|
end
|
|
local kernel = {};
|
|
|
|
local two_sigma_square = 2 * sigma * sigma;
|
|
local centre = (dimension - 1) / 2;
|
|
|
|
local sum = 0
|
|
for i = 0, dimension-1 do
|
|
for j = 0, dimension-1 do
|
|
local distance = wea_c.hypotenuse(i, j, centre, centre)
|
|
|
|
-- The following is an algorithm that came from the gaussian blur
|
|
-- wikipedia page [1].
|
|
--
|
|
-- http://en.wikipedia.org/w/index.php?title=Gaussian_blur&oldid=608793634#Mechanics
|
|
local gaussian = (1 / math.sqrt(
|
|
math.pi * two_sigma_square
|
|
)) * math.exp((-1) * ((distance ^ 2) / two_sigma_square));
|
|
|
|
sum = sum + gaussian
|
|
kernel[i*dimension + j] = gaussian
|
|
end
|
|
end
|
|
|
|
-- Returns the unit vector of the kernel array.
|
|
for k,v in pairs(kernel) do
|
|
kernel[k] = kernel[k] / sum
|
|
end
|
|
|
|
return true, kernel
|
|
end
|