_ff_cgpt_catch_functions.lua

It can be difficult to predict what assumptions the original author made about the environment in which the script would be run, or how the output should be formatted. But by breaking down the code and understanding what each piece is doing, you can usually figure out how to adapt it to work in Filter Forge.

the map script requires this format: 

function prepare()
	-- called once, before the rendering begins.
	-- used for non-mapped inputs and precalculation.
end;

function get_sample(x, y)
	-- main function returning image output.
	-- used for mapped inputs and mage generation.
    local r, g, b, a = 0, 0, 0, 1			-- initialize when not input
	local , g, b = x, y, (x + y) / 2		-- default gradient output
	return r, g, b, a
end;


-function add_vector_gradients(x, y, num_dimensions, resolution)
	local gradients = {{1, 0}, {0, 1}} -- x and y gradients
	for i = 1, num_dimensions do
		table.insert(gradients, {1 / resolution, -1 / resolution})
	end
	return unpack(gradients)
end
	-- x, y, z, w = add_vector_gradients(x, y, 2, 600)


function get_sample_color(x, y, r, g, b, a)
	local r, g, b, a = x * y * r, x * y * g, x * y * b,  x * y * a
	return r, g, b, a
end
	-- r_, g_, b_, a_ = get_sample_color(x, y, 1, 1, 1, 1)
	-- r_atm, g_atm, b_atm, a_atm = get_sample_color(x, y, 0.055, 0.5775, 1.1, 1)


-[[
	local sqrt, min, max, rad, pi = math.sqrt, math.min, math.max, math.rad, math.pi
	local sin, cos, tan, asin, acos, atan2 = math.sin, math.cos, math.tan, math.asin, math.acos, math.atan2
-- prepare
	-- inputs and precalculation
	ang_x = rad(get_angle_input(ANGLE_X)) 
	ang_y = rad(get_angle_input(ANGLE_Y))
	ang_z = rad(get_angle_input(ANGLE_Z))

	cos_ax, sin_ax  = cos(ang_x), sin(ang_x)
	cos_ay, sin_ay = cos(ang_y), sin(ang_y)
	cos_az, sin_az = cos(ang_z), sin(ang_z)
]]
function get_map_rotations_xyz(x, y)
	local x = x - 0.5
	local y = y * pi
	x = x * aspect * pi
	local nx = cos(x) * sin(y)
	local ny = sin(x) * sin(y)
	local nz = cos(y)
	local ax1, ax2 = (nx * cos_ax) + (ny * sin_ax), (nx * sin_ax) - (ny * cos_ax)
	local ay1, ay2 = (ax1 * cos_ay) - (cos(y) * sin_ay), (ax1 * sin_ay) + (cos(y) * cos_ay)
	local az1, az2 = (ax2 * cos_az) + (ay2 * sin_az), (ax2 * sin_az) - (ay2 * cos_az)
	nx = atan2(az1, ay1) * 0.159155 + 0.5
	ny = acos(az2) * 0.16 * 2
	nx = xratio(nx) -- aspect auto-conversion
	return nx, ny
end;


function xratio(x)
	if OUTPUT_WIDTH / OUTPUT_HEIGHT == 2 then x = x * 2 - 1 end;
	return x
end;
	-- x = xratio(x) -- in get_sample or function


local function cos_sin(angle)
	local cos_angle, sin_angle = cos(angle), sin(angle)
	return cos_angle, sin_angle
end;
	-- c_, s_ = cos_sin(angle) -- in prepare or function


function get_cos_sin(rotation, tilt, roll)
	local rotation, tilt, roll = rotation, tilt, roll
	cy, sy = cos_sin(rotation) -- y-axis aka yaw
	cx, sx = cos_sin(tilt) -- x-axis aka pitch
	cz, sz = cos_sin(roll) -- z-axis
	return cy, sy, cx, sx, cz, sz
end;
	-- cy_, sy_, cx_, sx_, cz_, sz_ = get_cos_sin(rotation_, tilt_, roll_) -- in prepare


function get_sphere(x, y)
	local x, y = x * 2 - 1, y * 2 - 1
	x, y = x * radius, y * radius
	local rho = sqrt((x * x)+(y * y))
	local tha, phi = atan2(y, x), 0
	if per > 0 then
		phi = min(1, rho) * per
		local h, cph = sin(phi), cos(phi)
		rho = h * (cph* _div - sqrt((cph * cph - cp * cp)* _div* _div))
	end;
	px, py = rho * cos(tha), rho * sin(tha)
	local z = -sqrt(1.0 - ((x * x)+(y * y)))
	return x, y, z, rho, phi, tha
end;
	-- x_, y_, z_, rho_, phi_, tha_ = get_sphere(x, y) -- in get_sample


function rotate_sphere(x, y, z, cy, sy, cx, sx, cz, sz)
	x, y = rotate_z(x, y, z) -- roll
	z, y = rotate_x(x, y, z) -- tilt
	x, z = rotate_y(x, y, z) -- rotation
	return x, y, z
end;


function rotate_z(x, y, z) -- z-axis -- roll
	local tx, ty = (cz * x) - (sz * y), (sz * x) + (cz * y)
	x, y = tx, ty
	return x, y
end;


function rotate_x(x, y, z) -- x-axis -- tilt
	local tz, ty = (cx * z) - (sx * y), (sx * z) + (cx * y)
	z, y = tz, ty
	return z, y
end;


function rotate_y(x, y, z) -- y-axis -- rotation
	local tx, tz= (cy * x) - (sy * z), (sy * x) + (cy * z)
	x, z = tx, tz
	return x, z
end;


function rotate_xy(x, y, rotation) -- tha, phi
	x, y = min(max(x, - 1), 1), - min(max(y, - 1), 1)
	local phi, tha = asin(y), 0
	local cph = cos(phi)
	x = min(max(x, - cph), cph)
	if cph~=0 then tha = asin(x / cph) end;
	phi = .5 * pi - phi
	local nx, ny, nz = cos(tha) * sin(phi), sin(tha) * sin(phi), cos(phi)
	nx, nz = nx * cx_1 - nz * sx_1, nx * sx_1 + nz * cx_1 -- tilt
	tha, phi = atan2(ny, nx) + rotation, acos(nz) -- rotation
	tha, phi = (tha * pi_div + 1) * .5, phi * pi_div
	tha = xratio(tha) -- aspect auto-conversion
	return tha, phi -- relative x, y
end;


function get_atmos(x, y, alpha, rho)
	local x, y, alpha, rho = x, y, alpha, rho
	local atmos, phi = 1, min(1, rho)
	local s_atmos, c_atmos = sin(atmos), cos(atmos)
	local s_phi, c_phi = sin(phi), cos(phi)
	rho = s_phi * (c_phi / pi - sqrt((c_phi * c_phi - c_atmos * c_atmos) / (pi ^ 2))) * 10
	atmos = -sqrt(max(1.0 - ((x * x)+(y * y)), 0.0000001))
	atmos = (atmos * 0.5 + 0.5) * 2
	return atmos
end;
	-- atmos = get_slider_input(ATMOS) * 0.25 * pi; s_atmos, c_atmos = sin(atmos), cos(atmos); divp = max(1 / s_atmos)
	-- if atmos > radius then alpha = 0 end; return alpha * atmos, atmos, alpha


a lua map script for cos and sin of an angle:

local function cos_sin(angle)
	local cos_angle, sin_angle = cos(angle), sin(angle)
	return cos_angle, sin_angle
end;
	-- _ac, _as = cos_sin(angle)

a lua map script for cartesian to bi-polar remapping:

function prepare()
	aspect = OUTPUT_HEIGHT / OUTPUT_WIDTH * 2
	mode = get_checkbox_input(MODE) and true or false
end;

function get_sample(x, y)
	local z = (1 - y) * 2 - 1
	local nz = 1 - x
	local x = x * aspect * math.pi
	local y = y * math.pi
	local nx = math.cos(x) * math.sin(y)
	local ny = (math.sin(x) * math.sin(y))
	-- nx = nx * 0.5 + 0.5
	-- ny = ny * 0.5 + 0.5
	-- poles to equator
	-- local nnx = (math.atan(z, nx) / math.pi) * 0.5 + 0.5
	-- local nny = ny * 0.5 + 0.5
	-- poles to poles
	local nnx = (math.atan(z, nx) / math.pi)5
	local nny = ny
	r = nnx
	g = nny
	b = 0.8235294118 -- nz
	if mode then 
		return r, g, b, 1
	else
		r, g, b, a = get_sample_map(nnx, nny, SOURCE)
		return r, g, b, a
	end
end;

a lua map script for equirectangular remapping:

function prepare()
	-- inputs and precalculation
	aspect = OUTPUT_HEIGHT / OUTPUT_WIDTH * 2
end;

function get_sample(x, y)
	-- image generation
	local nx, ny, nz = map_equirectangular(x, y)
	local r, g, b, a = nx, ny, nz, 1
	return r, g, b, a
end;

function map_equirectangular(x, y)
	-- equirectangular remapping
	local x = x * aspect * math.pi
	local y = y * math.pi
	local nx = math.cos(x) * math.sin(y)
	local ny = math.sin(x) * math.sin(y)
	local nz = math.cos(y)
	return nx, ny, nz
end;
--	local nx, ny, nz = map_equirectangular(x, y)


a lua function to convert radians to rotations

function rad2rot(x) return x * 0.159155 end -- or / 6.2832

a lua function to clamp a value to 0 to 1 range:

function truncate(value) -- truncate()
	if value <= 0 then value = 0 end
	if value >= 1 then value = 1 end
	return value
end;

a lua function to modify any variables that must not be zero (epsilon):

function e(x)
  if math.abs(x) < 1e-10 then
    return 1e-10
  else
    return x
  end
end

function reciprocal(x)
-- calculate the reciprocal of a variable, making sure it's not zero
  return 1 / e(x)
end


a lua function that sums all the arguments passed to it:

function sum(...)
  local result = 0
  for i, v in ipairs({...}) do
    result = result + v
  end
  return result
end
--[[
	the ... notation in the function definition allows the sum function to accept any number of arguments. the ipairs({...}) expression inside the function body creates an iterator over the table of arguments passed to the function, allowing them to be accessed and summed.
]]--

a lua function to convert a value from one range of numbers to another:

function convert_range(old_min, old_max, new_min, new_max, value)
  local old_range = old_max - old_min
  local new_range = new_max - new_min
  local normalized_value = (value - old_min) / old_range
  return new_min + (normalized_value * new_range)
end
--[[
	this function takes in the old minimum and maximum values (0 and 100, respectively), as well as the new minimum and maximum values (0 and 1, respectively), and the value to convert (50). it then calculates the normalized value of the input value, and returns the converted value in the new range (in the example: 0.5).
]]--

a lua function to convert one range of numbers to another that returns the conversion ratio and adjustment value for the new range or a converted value if provided:

function convert_range(old_min, old_max, new_min, new_max, value)
    local old_range = old_max - old_min
    local new_range = new_max - new_min
    local ratio = new_range / old_range
    local adjustment = new_min - old_min * ratio
    if value == nil then
        return ratio, adjustment
    else
        return value * ratio + adjustment
    end
end
--[[
	this function takes the old_min, old_max, new_min, new_max, value arguments and returns value in the new range, or the conversion ratio and adjustment value if value is not supplied. 

	if you supply -1, 1, 0, 1 as the arguments to the convert_range function, you will get a ratio of 0.5 and an adjustment value of 0.5, since:
	• old_min is -1; old_max is 1; new_min is 0; 	new_max is 1
	the ratio can be calculated as:

	ratio = (new_max - new_min) / (old_max - old_min)
	• = (1 - 0) / (1 - (-1))
	• = 0.5
	the adjustment value can be calculated as:

	adjustment = new_min - (ratio * old_min)
	• = 0 - (0.5 * (-1))
	• = 0.5
	so, if you call convert_range(-1, 1, 0, 1), you will get 0.5 as the ratio and 0.5 as the adjustment value.
]]--


a lua map script exploiting a function to convert a value from one range of numbers to another or return an rgb value,ratio and adjustment:

function prepare()
	-- inputs and precalculation
	mode = get_checkbox_input(MODE)
end;

function get_sample(x, y)
	-- inputs and image generation
	local r, g, b, a = get_sample_map(x, y, SOURCE)
	old_min = get_sample_grayscale(x, y, FROM_MIN)
	old_max = get_sample_grayscale(x, y, FROM_MAX)
	new_min = get_sample_grayscale(x, y, TO_MIN)
	new_max = get_sample_grayscale(x, y, TO_MAX)
	if mode then
		--- average channels
		value = r +g +b / 3
		-- fill channels with `value * ratio + adjustment, ratio, adjustment`
		r, g, b = convert_range(old_min, old_max, new_min, new_max, value, mode)
	else
		r = convert_range(old_min, old_max, new_min, new_max, r, mode)
		g = convert_range(old_min, old_max, new_min, new_max, g, mode)
		b = convert_range(old_min, old_max, new_min, new_max, b, mode)
	end;
	return r, g, b, a
end;

function convert_range(old_min, old_max, new_min, new_max, value, mode)
    local old_range = old_max - old_min
    local new_range = new_max - new_min
    local ratio = new_range / old_range
    local adjustment = new_min - old_min * ratio
    if mode then
 		return value * ratio + adjustment, ratio, adjustment
    else
       return value * ratio + adjustment
	end;
end;


a function that calculates the angle offsets of three 2D offsets:

function calculate_angle(x, y)
    return math.atan2(y, x) * 180 / math.pi
end
	-- this code defines a function calculate_angle that takes an x and y offset and returns the angle offset in degrees. the main code then defines an array of three 2d offsets and uses a loop to calculate the angle offset for each one using the calculate_angle function. the results are printed to the console.

function offset_image(x, y, img)
	-- Three 2D offsets
	offsets = {
		{0.02, 0},
		{-0.015, 0},
		{-0.015, -0.02}
	}

	-- Calculate the angle offset for each offset
	for i, offset in ipairs(offsets) do
		angle = calculate_angle(offset[1], offset[2])
		-- print(string.format("Offset %d: %.2f degrees", i, angle))
	end

	-- establish lookup table
	local lookup = {}
	for x = 1, width do
		lookup[x] = {}
		for y = 1, height do
			local i = math.floor((x-1)/(1/grid_size)) + 1
			local j = math.floor((y-1)/(1/grid_size)) + 1
			lookup[x][y] = grid[i][j]
		end
	end

	-- set the pixel values of the output image based on the grid cells
	for x = 1, width do
		for y = 1, height do
			local cell = lookup[x][y]
			img:set_pixel(x-1, y-1, cell[1], cell[2], cell[3], cell[4]) -- set_pixel function may not exist, just here as an example
		end
	end

	-- return the output image
	return img
end



•• I would also like a general `lookup` function for use in a Filter Forge map script component that can use the images from two `get_sample_map` functions `x_lookup` and `y_lookup` and use them as gradients to remap a `source` `get_sample_map` image.

Here's an example of a general lookup function in Lua that uses two input images, x_lookup and y_lookup, as gradients to remap a source image:

function lookup(source, x_lookup, y_lookup) --<!> adapt to ff standards
	 -- get the dimensions of the input images
	 local width, height = source.width, source.height
	 local x_width, x_height = x_lookup.width, x_lookup.height
	 local y_width, y_height = y_lookup.width, y_lookup.height

	 -- create an output image with the same dimensions as the source; make_output_image() is merely an example
	 local output = make_output_image()
	 output.width, output.height = width, height

	 -- iterate over each pixel in the output image
	 for y = 0, height - 1 do
			for x = 0, width - 1 do
				 -- get the color value of the current pixel in the source image
				 local r, g, b, a = source:get_pixel(x, y)

				 -- use the x_lookup and y_lookup images as gradients to remap the color values
				 local x_value = x_lookup:get_pixel(x % x_width, y % x_height).r
				 local y_value = y_lookup:get_pixel(x % y_width, y % y_height).r
				 r = r * x_value
				 g = g * y_value
				 b = b * (1 - x_value) * (1 - y_value)

				 -- set the color value of the current pixel in the output image
				 output:set_pixel(x, y, r, g, b, a)
			end
	 end

	 return output
end
	--[[
		here's how to use this lookup function:

		» define two input images, x_lookup and y_lookup, using the get_sample_map function.
		» define a source image using the get_sample_map function.
		» call the lookup function with the source, x_lookup, and y_lookup images as arguments.
		» use the output of the lookup function as the result of the Filter Forge map script component.
		» note: this is a general example, so the specific implementation may need to be adjusted to fit the specific use case.
	]]--



A version of the `lookup` function, `lookup_in`, that can use `xin` and `yin (derivatives of the`x` and `y` gradients of the `get_sample` function which have undergone modifications) as substitutes for the `x_lookup, y_lookup` to remap `source`.

function lookup_in(xin, yin, source)
		local sourceWidth, sourceHeight = get_source_image_size(source)
		local x, y = xin * sourceWidth, yin * sourceHeight
		local x1, y1 = math.floor(x), math.floor(y)
		local x2, y2 = x1 + 1, y1 + 1
		local wx2, wy2 = x - x1, y - y1
		local wx1, wy1 = 1.0 - wx2, 1.0 - wy2

		local s11 = get_sample(source, x1, y1)
		local s21 = get_sample(source, x2, y1)
		local s12 = get_sample(source, x1, y2)
		local s22 = get_sample(source, x2, y2)

		local w1 = wx1 * wy1
		local w2 = wx2 * wy1
		local w3 = wx1 * wy2
		local w4 = wx2 * wy2

		local x_gradient = (s21 - s11) + wx2 * (s22 - s21 - s12 + s11)
		local y_gradient = (s12 - s11) + wy2 * (s22 - s21 - s12 + s11)

		local r = w1 * get_sample(source, x1, y1) + w2 * get_sample(source, x2, y1) + w3 * get_sample(source, x1, y2) + w4 * get_sample(source, x2, y2)
		local g = w1 * get_sample(xin, x1, y1) + w2 * get_sample(xin, x2, y1) + w3 * get_sample(xin, x1, y2) + w4 * get_sample(xin, x2, y2)
		local b = w1 * get_sample(yin, x1, y1) + w2 * get_sample(yin, x2, y1) + w3 * get_sample(yin, x1, y2) + w4 * get_sample(yin, x2, y2)
		local a = w1 * get_sample(source, x1, y1, CHANNEL_ALPHA) + w2 * get_sample(source, x2, y1, CHANNEL_ALPHA) + w3 * get_sample(source, x1, y2, CHANNEL_ALPHA) + w4 * get_sample(source, x2, y2, CHANNEL_ALPHA)

		return r, g, b, a, x_gradient, y_gradient
end
		-- here, `xin` and `yin` are used in place of `x_lookup` and `y_lookup` to sample the gradients. the rest of the function remains the same.


Modified `lookup_in` function with descriptive comments:

function lookup_in(source, xin, yin, x_size, y_size)
	-- remaps the 'source' image based on the xin and yin derivatives of the gradients
	-- (or lookup tables) specified in x_lookup and y_lookup.
	-- x_size and y_size specify the dimensions of the source image and output image.
	-- the resulting image is returned as an array of r,g,b,a values.
		-- Initialize an array to store the output image.
		local output = {}

		-- loop through every pixel in the output image.
		for y = 0, y_size - 1 do
				for x = 0, x_size - 1 do
						-- calculate the remapped coordinates for this pixel using the xin and yin gradients.
						local u = xin[y * x_size + x + 1]
						local v = yin[y * x_size + x + 1]

						-- clamp the coordinates to the range [0, 1].
						u = math.max(0, math.min(1, u))
						v = math.max(0, math.min(1, v))

						-- convert the clamped coordinates to pixel coordinates in the source image.
						local sx = math.floor(u * x_size + 0.5)
						local sy = math.floor(v * y_size + 0.5)

						-- get the color of the corresponding pixel in the source image.
						local color = source[sy * x_size + sx + 1]

						-- add the color to the output array.
						table.insert(output, color[1])
						table.insert(output, color[2])
						table.insert(output, color[3])
						table.insert(output, color[4])
				end
		end

		-- return the output array.
		return output
end


•• A passing thought, would it be possible for you to write a Sobel edge-detect function in Lua for use in Filter Forge?
Yes, I can provide you with a Sobel edge-detection function written in Lua for use in Filter Forge. Here is an implementation of the Sobel edge detection algorithm that you can use:

function sobel(input)
    local width, height = input.width, input.height
    local output = {}

    for y = 1, height do
        for x = 1, width do
            local gx = (-1 * input:get(x - 1, y - 1)) + (-2 * input:get(x - 1, y)) + (-1 * input:get(x - 1, y + 1)) +
                       (1 * input:get(x + 1, y - 1)) + (2 * input:get(x + 1, y)) + (1 * input:get(x + 1, y + 1))
            local gy = (-1 * input:get(x - 1, y - 1)) + (-2 * input:get(x, y - 1)) + (-1 * input:get(x + 1, y - 1)) +
                       (1 * input:get(x - 1, y + 1)) + (2 * input:get(x, y + 1)) + (1 * input:get(x + 1, y + 1))
            local magnitude = math.sqrt(gx ^ 2 + gy ^ 2)
            output:set(x, y, magnitude)
        end
    end

    return output
end

This function takes an input image as an argument, which is assumed to be a Filter Forge Buffer. The function calculates the gradient of the image using the Sobel operator, and returns an output image that represents the magnitude of the gradient at each pixel.

Note that this implementation assumes that the input image has a border of one pixel around its edges. If your input image does not have a border, you may need to modify the function accordingly.

•• It would be preferrable not to have one. If it creates too much difficulty, I can come up wit a work-around, like first scaling down the image by 1 pixel, doing the edge-detect, then scaling back up once it's done.

In that case, you can modify the sobel function to handle the case where the input image does not have a border. One way to do this is to calculate the gradient using only the pixels that are inside the image, and then set the border pixels of the output image to zero. Here's an updated implementation of the sobel function that works without assuming a border:

function sobel(input)
    local width, height = input.width, input.height
    local output = Buffer:new(width, height)

    for y = 2, height - 1 do
        for x = 2, width - 1 do
            local gx = (-1 * input:get(x - 1, y - 1)) + (-2 * input:get(x - 1, y)) + (-1 * input:get(x - 1, y + 1)) +
                       (1 * input:get(x + 1, y - 1)) + (2 * input:get(x + 1, y)) + (1 * input:get(x + 1, y + 1))
            local gy = (-1 * input:get(x - 1, y - 1)) + (-2 * input:get(x, y - 1)) + (-1 * input:get(x + 1, y - 1)) +
                       (1 * input:get(x - 1, y + 1)) + (2 * input:get(x, y + 1)) + (1 * input:get(x + 1, y + 1))
            local magnitude = math.sqrt(gx ^ 2 + gy ^ 2)
            output:set(x, y, magnitude)
        end
    end
    
    -- Set border pixels to zero
    for x = 1, width do
        output:set(x, 1, 0)
        output:set(x, height, 0)
    end
    for y = 1, height do
        output:set(1, y, 0)
        output:set(width, y, 0)
    end

    return output
end
This implementation skips the outermost row and column of pixels when calculating the gradient, and then sets the border pixels of the output image to zero using a separate loop. This ensures that the output image has the same dimensions as the input image, but with zeros in the border pixels where the gradient could not be calculated.


function tableToGrid(table)
		local grid = {}
		for y=0,1,0.01 do
				for x=0,1,0.01 do
						local r, g, b, a = 0, 0, 0, 0
						for i=1,#table do
								local dx, dy, dz, dw = x-table[i][1], y-table[i][2], 0, 0
								if #table[i] >= 3 then dz = table[i][3] end
								if #table[i] >= 4 then dw = table[i][4] end
								local attn = 2 - dx^2 - dy^2 - dz^2 - dw^2
								if attn > 0 then
										attn = attn^4
										r = r + attn * table[i][1]
										g = g + attn * table[i][2]
										b = b + attn * dz
										a = a + attn * dw
								end
						end
						grid[#grid+1] = r
						grid[#grid+1] = g
						grid[#grid+1] = b
						grid[#grid+1] = a
				end
		end
		return grid
end
	--[[
		a lua script function for use in a Filter Forge map script component that can turn a table with 2 to 4 coordinate values (x,y,z,w) into an x,y grid with cells showing `x,y,z,w` as r,g,b,a values. this function takes a table as an argument and returns a flattened grid of r,g,b,a values. you can use the returned grid to create an image.

		note that `tableToGrid(table)` assumes that the values in the table are in the range of -1 to 1. If your values are in a different range, you may need to modify the function accordingly.
	]]--

function process()
	--[[
		display the `grid` from `tableToGrid` in r,g,b,a showing the colored cells arranged in x,y = (0 to 1), (0 to 1) as an image in Filter Forge.
		uses the following code in the process() function of a Filter Forge map script component:
		get the width and height of the image
		
		this code first gets the width and height of the input image using the get_size() function. it then creates a new image using the make_image() function with the same dimensions as the input image.

		next, it creates a lookup table to map x,y coordinates to the corresponding grid cells. this is done by dividing the width and height of the image into equal-sized regions based on the size of the grid, and mapping each region to the corresponding grid cell.

		finally, it sets the pixel values of the output image based on the corresponding grid cell using the set_pixel() function. the r,g,b,a values of the cell are used to set the pixel values.

		the code then returns the output image, which will be displayed in Filter Forge.
	]]--
	local width, height = get_size()

	-- create a new image with the same dimensions as the input image
	local img = make_image(width, height)

	-- create a lookup table to map x,y coordinates to the grid cells
	local grid_size = #grid[1]
	--[[
	`local grid_size = #grid[1]` creates a local variable called `grid_size` and sets its value to the length of the first sub-table of the `grid` table. in lua, the `#` operator is used to get the length of a table, which is the number of elements in the table when the table has consecutive integer keys starting from 1. in this case, `grid[1]` is a sub-table of the `grid` table, and `#grid[1]` returns the number of elements in this sub-table, which is also the number of cells in a row or column of the `grid` table assuming it's a square grid. the `local` keyword means that the variable is only accessible within the scope of the block of code where it is defined.
	]]--
	

Updated version of the `tableToGrid function` that automatically determines the size of the output image:

function tableToGrid(table)
	local grid_size = #table[1]
	local output_size = OUTPUT_HEIGHT * OUTPUT_WIDTH
	local grid_step = 1 / grid_size
	local output = {}
	
	for i = 1, output_size do
		local x = (i - 1) % OUTPUT_WIDTH
		local y = math.floor((i - 1) / OUTPUT_WIDTH)
		local x_idx = math.floor(x / grid_step) + 1
		local y_idx = math.floor(y / grid_step) + 1
		
		local r, g, b, a = unpack(table[y_idx][x_idx])
		table.insert(output, r)
		table.insert(output, g)
		table.insert(output, b)
		table.insert(output, a)
	end
	
	return output
end
    -- this version of the function calculates the output size as the product of OUTPUT_HEIGHT and OUTPUT_WIDTH, and uses these values to determine the x and y coordinates of each pixel in the output image.


function get_noise(x,y,z) -- demo reliant on unknown library
	local noise = 0
	if noise_type == 1 then
		noise = math.perlin_noise(x,y,z)
	elseif noise_type == 2 then
		noise = math.simplex_noise(x,y,z)
	elseif noise_type == 3 then
		noise = math.cellular_noise(x,y,z)
	elseif noise_type == 4 then
		noise = math.fractal_noise(x,y,z)
	end
	return noise
end