So, starting from SVG data, you generate an Image object from it then draw that Image as needed. Depending on the shape and its size, it's a bit lighter to have it described as SVG data than as a PNG file in your game assets.
Github link:
https://github.com/RNavega/RasterPolygon-Love
- Preview.png (14.97 KiB) Viewed 1209 times
A .love file is attached, but if you just want to read the code then here's the main.lua:
Code: Select all
-- ==========================================================
-- Example of rasterizing a simple polyline polygon.
-- By Rafael Navega (2024)
--
-- License: Public Domain
-- ==========================================================
io.stdout:setvbuf('no')
local ffi = require('ffi')
local UINT8_PTR_TYPEOF = ffi.typeof('uint8_t*')
local FLOAT_PTR_TYPEOF = ffi.typeof('float*')
local SIZEOF_FLOAT = ffi.sizeof('float')
local polygonImage1
local polygonImage2
local r8Shader
-- Returns a LÖVE ByteData object, as well as its uint8_t FFI pointer.
-- The pointer is for modifying the contents.
-- Use makeFloatData() when you need it for a GLSL uniform.
local function makeByteData(totalBytes)
local data = love.data.newByteData(totalBytes)
return data, UINT8_PTR_TYPEOF(data:getFFIPointer())
end
-- For use with GLSL uniforms. Unused in this demo.
local function makeFloatData(totalFloats)
local data = love.data.newByteData(totalFloats * SIZEOF_FLOAT)
return data, FLOAT_PTR_TYPEOF(data:getFFIPointer())
end
local function svgPolygonPointsString()
-- From the Inkscape XML editor (Ctrl + Shift + X), copy-pasting
-- the text from the "d" attribute (the SVG draw commands).
return [[
M 0,0
V 32
H 32
V 0
Z
M 2,2
H 30
V 30
H 2
Z
M 9.49,3 9.11,3.03 8.76,3.21 4.06,6.89 3.8,7.2 3.69,7.56 3.71,7.94
3.89,8.29 10.66,16.91
l -2.35,1.85 -0.16,0.22 -0.01,0.26 0.12,0.23 0.24,0.13 10.47,2.46
h 0.36
l 0.31,-0.15 0.22,-0.27 0.08,-0.35 0.1,-10.76 -0.08,-0.26 -0.19,-0.17
-0.25,-0.05 -0.25,0.1 -2.35,1.84
L 10.16,3.37 9.86,3.12
Z
M 20.5,24 17.58,24.2 15.2,24.73 13.59,25.53 13,26.5
l 0.59,0.97 1.61,0.79 2.38,0.54
L 20.5,29 23.42,28.8 25.8,28.27 27.41,27.47 28,26.5 27.41,25.53
25.8,24.73 23.42,24.2
Z
]]
end
-- Pixel shader to draw an image in the format "r8" (only a red channel).
-- This is needed because if no shader is used, the result is tinted red.
local R8_PIXEL_SOURCE = [[
vec4 effect( vec4 color, Image tex, vec2 texture_coords, vec2 screen_coords )
{
float alpha = Texel(tex, texture_coords).r;
const vec4 HALF_GREY = vec4(vec3(0.5), 1.0);
return mix(HALF_GREY, vec4(color.xyz, 1.0), alpha);
}
]]
-- Parses the SVG "d" attribute draw command list.
-- Only linear drawings are supported (M/m, L/l, H/h and V/v).
-- Curve, arc (C/c, S/s, A/a) etc commands would need to be flattened to lines
-- to be supported.
local function parseSVGDrawCommands(commandString)
local tableInsert = table.insert
local state, lowerState
local shapeData = {shapes={}}
local currentShape = {}
local length = 0
local position = {0.0, 0.0}
-- Split the "d" string by whitespace, go through each non-whitespace piece.
for piece in commandString:gmatch('%s*([^%s]+)%s*') do
lowerPiece = piece:lower()
if (lowerPiece == 'm' or lowerPiece == 'l'
or lowerPiece == 'h' or lowerPiece == 'v') then
state = piece
lowerState = lowerPiece
elseif lowerPiece == 'z' then
currentShape.length = length
tableInsert(shapeData.shapes, currentShape)
currentShape = {}
length = 0
else
-- Try to read a single number ("135.002"), or a comma-separated
-- pair of numbers ("135.002,-99.71"), with the numbers possibly
-- having decimal points and/or preceded by a negative sign.
local valueA, valueB = piece:match('([%-%d%.]+)[,]*([%-%d%.]*)')
if valueA then
valueA = tonumber(valueA)
if lowerState == 'l' or lowerState == 'm' then
if valueB then
valueB = tonumber(valueB)
if state == 'M' or state == 'L' then
position[1] = valueA
position[2] = valueB
else
position[1] = position[1] + valueA
position[2] = position[2] + valueB
end
currentShape[length + 1] = position[1]
currentShape[length + 2] = position[2]
length = length + 2
else
error(('Bad "%s" command parameters: %s'):format(state, piece), 2)
end
elseif lowerState == 'h' or lowerState == 'v' then
local axisIndex = (lowerState == 'h') and 1 or 2
if state == 'H' or state == 'V' then
position[axisIndex] = valueA
else
position[axisIndex] = position[axisIndex] + valueA
end
currentShape[length + 1] = position[1]
currentShape[length + 2] = position[2]
length = length + 2
else
error('No active SVG drawing state', 2)
end
else
error('Unsupported SVG draw command: '.. piece, 2)
end
end
end
return shapeData
end
local function makeRasterPolygon(shapeData, scaleX, scaleY)
-- Default scale values if omitted.
scaleX = scaleX or 1.0
scaleY = scaleY or 1.0
local rasterPolygon = {length=nil, width=nil, height=nil}
local bbx1 = math.huge
local bby1 = math.huge
local bbx2 = -math.huge
local bby2 = -math.huge
local totalSegments = 0
-- The p0 and p1 below are from "p1 = p0 + v . t"
for shapeIndex = 1, #shapeData.shapes do
local pointData = shapeData.shapes[shapeIndex]
local p0 = {pointData[pointData.length - 1] * scaleX,
pointData[pointData.length] * scaleY}
for pairIndex = 1, pointData.length, 2 do
local p1 = {pointData[pairIndex] * scaleX,
pointData[pairIndex + 1] * scaleY}
-- Find the bounding box.
if p1[1] < bbx1 then
bbx1 = p1[1]
elseif p1[1] > bbx2 then
bbx2 = p1[1]
end
if p1[2] < bby1 then
bby1 = p1[2]
elseif p1[2] > bby2 then
bby2 = p1[2]
end
-- Store a new line segment object into the polygon table.
local deltaX = p1[1] - p0[1]
local deltaY = p1[2] - p0[2]
local segmentData = {p0 = p0,
p1 = p1,
v = {deltaX, deltaY},
lengthSq = (deltaX * deltaX + deltaY * deltaY)}
totalSegments = totalSegments + 1
rasterPolygon[totalSegments] = segmentData
p0 = p1
end
end
rasterPolygon.length = totalSegments
rasterPolygon.width = bbx2
rasterPolygon.height = bby2
return rasterPolygon
end
-- Returns the (estimated) coverage of the polygon over the point, as a
-- value in the range [0.0, 1.0], with 1.0 being "fully covered".
local function sampleRasterPolygon(x, y, rasterPolygon)
-- Sample from the pixel centers.
x = x + 0.5
y = y + 0.5
local isInside = false
local nearestDistance = math.huge
local distanceTG = 0.0
for segmentIndex = 1, rasterPolygon.length do
local segmentData = rasterPolygon[segmentIndex]
local p0 = segmentData.p0
local p1 = segmentData.p1
local v = segmentData.v
local deltaX = x - p0[1]
local deltaY = y - p0[2]
-- Only raycast on non-horizontal segments, and segments where
-- the point is contained in the vertical span of the segment.
-- This initial test condition is based on W. Randolph Franklin's
-- point-in-poly algorithm (MIT licensed) from:
-- https://wrfranklin.org/Research/Short_Notes/pnpoly.html#The%20C%20Code
if ((p0[2] > y) ~= (p1[2] > y)) then
local tX = deltaY / v[2]
local intersectX = p0[1] + v[1] * tX
if x < intersectX then
isInside = not isInside
end
end
local otherX, otherY
local dot = (deltaX * v[1] + deltaY * v[2]) / segmentData.lengthSq
if dot <= 0.0 then
otherX = p0[1]
otherY = p0[2]
elseif dot >= 1.0 then
otherX = p1[1]
otherY = p1[2]
else
otherX = p0[1] + v[1] * dot
otherY = p0[2] + v[2] * dot
end
local deltaX = x - otherX
local deltaY = y - otherY
local distance = math.sqrt(deltaX * deltaX + deltaY * deltaY)
if distance < nearestDistance then
nearestDistance = distance
-- A pixel is shaped like a square, so there's two possible distances
-- to its center: from its sides (half the square side) or from its
-- corners (half the diagonal of the square).
-- When coming from a corner to its center, that distance measures
-- "half of the side, multiplied by the square root of two".
--
-- We find the slope ratio (like a tangent function) of the vector from
-- the nearest point of the polygon towards the center of the pixel.
-- This slope goes from 0.0 when it's orthogonal to the square sides, and
-- up to 1.0 when it's orthogonal to the diagonals / square corners.
-- Later this tangent value is used as a weight to mix between the
-- "half-side" and "half-diagonal" lengths, so that the interpolated length
-- is the reference length to estimate how far that the polygon is covering
-- the square shape of the pixel.
-- See 'baseDistance' below.
deltaX = math.abs(deltaX)
deltaY = math.abs(deltaY)
if deltaX > deltaY then
distanceTG = deltaX ~= 0.0 and (deltaY / deltaX) or 0.0
else
distanceTG = deltaY ~= 0.0 and (deltaX / deltaY) or 0.0
end
end
end
local CENTER_DISTANCE = 0.5
-- Do a linear blending between 1.0 and sqrt(2), that is,
-- a + (b - a) * t.
-- Then use it to scale the half pixel distance, so it's in the
-- range [0.5, 0.5 * sqrt(2)].
local DIAG_OFFSET = 1.4142135623731 - 1.0
local scaleFactor = 1.0 + DIAG_OFFSET * distanceTG
local baseDistance = CENTER_DISTANCE * scaleFactor
-- Map the nearest distance to the estimated "coverage" on the pixel, a
-- value in the range [0.0, 1.0], in this way:
-- - From 0.0 when the pixel square is fully outside the polygon;
-- - Up to 0.5 when the pixel center is exactly at the polygon edge;
-- - Up to 1.0 when the pixel square is fully inside the polygon.
local coverage
if isInside then
coverage = (1.0 + nearestDistance / baseDistance) / 2.0
else
coverage = (1.0 - nearestDistance / baseDistance) / 2.0
end
-- Debug:
--local coverage = isInside and 1.0 or 0.0
-- Finally, clamp to the [0.0, 1.0] range
return coverage < 0.0 and 0.0 or (coverage > 1.0 and 1.0 or coverage)
end
local function rasterizePolygon(rasterPolygon)
local width = math.floor(rasterPolygon.width + 0.5)
local height = math.floor(rasterPolygon.height + 0.5)
local bytesPerPixel = 1
local bytesPerRow = width * bytesPerPixel
local data, ptr = makeByteData(height * bytesPerRow)
for y = 0, height - 1 do
local ptrOffset = y * bytesPerRow
for x = 0, width - 1 do
local fill = sampleRasterPolygon(x, y, rasterPolygon)
local byteX = x * bytesPerPixel
ptr[ptrOffset + byteX] = math.floor(fill * 255.0)
end
end
local imageData = love.image.newImageData(width, height, 'r8', data)
local image = love.graphics.newImage(imageData)
image:setWrap('clamp', 'clamp')
return image
end
function love.load()
local shapeData = parseSVGDrawCommands(svgPolygonPointsString())
local rasterPolygon = makeRasterPolygon(shapeData, 1.0, 1.0)
local rasterPolygon3x = makeRasterPolygon(shapeData, 3.0, 3.0)
love.window.setTitle('Polygon Rasterization Demo')
local contentWidth = rasterPolygon.width + rasterPolygon3x.width + 4 + 4 + 4
local contentHeight = rasterPolygon3x.height + 4 + 4
love.window.setMode(math.floor(contentWidth * 4.0 + 0.5),
math.floor(contentHeight * 4.0 + 0.5))
love.graphics.setDefaultFilter('nearest', 'nearest')
polygonImage1 = rasterizePolygon(rasterPolygon)
polygonImage2 = rasterizePolygon(rasterPolygon3x)
r8Shader = love.graphics.newShader(R8_PIXEL_SOURCE)
love.graphics.setShader(r8Shader)
end
function love.draw()
love.graphics.scale(4.0, 4.0)
love.graphics.draw(polygonImage1, 4, 4)
love.graphics.draw(polygonImage2, polygonImage1:getPixelWidth() + 4 + 4, 4)
end
function love.keypressed(key)
if key == 'escape' then
love.event.quit()
end
end
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