when defined(pixieSweeps):
import algorithm
proc pixelCover(a0, b0: Vec2): float32 =
## Returns the amount of area a given segment sweeps to the right
## in a [0,0 to 1,1] box.
var
a = a0
b = b0
aI: Vec2
bI: Vec2
area: float32 = 0.0
if (a.x < 0 and b.x < 0) or # Both to the left.
(a.x == b.x): # Vertical line
# Area of the rectangle:
return (1 - clamp(a.x, 0, 1)) * (min(b.y, 1) - max(a.y, 0))
else:
# y = mm*x + bb
let
mm: float32 = (b.y - a.y) / (b.x - a.x)
bb: float32 = a.y - mm * a.x
if a.x >= 0 and a.x <= 1 and a.y >= 0 and a.y <= 1:
# A is in pixel bounds.
aI = a
else:
aI = vec2((0 - bb) / mm, 0)
if aI.x < 0:
let y = mm * 0 + bb
# Area of the extra rectangle.
area += (min(bb, 1) - max(a.y, 0)).clamp(0, 1)
aI = vec2(0, y.clamp(0, 1))
elif aI.x > 1:
let y = mm * 1 + bb
aI = vec2(1, y.clamp(0, 1))
if b.x >= 0 and b.x <= 1 and b.y >= 0 and b.y <= 1:
# B is in pixel bounds.
bI = b
else:
bI = vec2((1 - bb) / mm, 1)
if bI.x < 0:
let y = mm * 0 + bb
# Area of the extra rectangle.
area += (min(b.y, 1) - max(bb, 0)).clamp(0, 1)
bI = vec2(0, y.clamp(0, 1))
elif bI.x > 1:
let y = mm * 1 + bb
bI = vec2(1, y.clamp(0, 1))
area += ((1 - aI.x) + (1 - bI.x)) / 2 * (bI.y - aI.y)
return area
proc intersectsInner*(a, b: Segment, at: var Vec2): bool {.inline.} =
## Checks if the a segment intersects b segment.
## If it returns true, at will have point of intersection
let
s1 = a.to - a.at
s2 = b.to - b.at
denominator = (-s2.x * s1.y + s1.x * s2.y)
s = (-s1.y * (a.at.x - b.at.x) + s1.x * (a.at.y - b.at.y)) / denominator
t = (s2.x * (a.at.y - b.at.y) - s2.y * (a.at.x - b.at.x)) / denominator
if s > 0 and s < 1 and t > 0 and t < 1:
at = a.at + (t * s1)
return true
type
Trapezoid = object
nw, ne, se, sw: Vec2
SweepLine = object
#m, x, b: float32
atx, tox: float32
winding: int16
proc toLine(s: (Segment, int16)): SweepLine =
var line = SweepLine()
line.atx = s[0].at.x
line.tox = s[0].to.x
# y = mx + b
# line.m = (s.at.y - s.to.y) / (s.at.x - s.to.x)
# line.b = s.at.y - line.m * s.at.x
line.winding = s[1]
return line
proc intersectsYLine(
y: float32, s: Segment, atx: var float32
): bool {.inline.} =
let
s2y = s.to.y - s.at.y
denominator = -s2y
numerator = s.at.y - y
u = numerator / denominator
if u >= 0 and u <= 1:
let at = s.at + (u * vec2(s.to.x - s.at.x, s2y))
atx = at.x
return true
proc binaryInsert(arr: var seq[float32], v: float32) =
if arr.len == 0:
arr.add(v)
return
var
L = 0
R = arr.len - 1
while L < R:
let m = (L + R) div 2
if arr[m] ~= v:
return
elif arr[m] < v:
L = m + 1
else: # arr[m] > v:
R = m - 1
if arr[L] ~= v:
return
elif arr[L] > v:
arr.insert(v, L)
else:
arr.insert(v, L + 1)
proc sortSegments(segments: var seq[(Segment, int16)], inl, inr: int) =
## Quicksort + insertion sort, in-place and faster than standard lib sort.
let n = inr - inl + 1
if n < 32: # Use insertion sort for the rest
for i in inl + 1 .. inr:
var
j = i - 1
k = i
while j >= 0 and segments[j][0].at.y > segments[k][0].at.y:
swap(segments[j + 1], segments[j])
dec j
dec k
return
var
l = inl
r = inr
let p = segments[l + n div 2][0].at.y
while l <= r:
if segments[l][0].at.y < p:
inc l
elif segments[r][0].at.y > p:
dec r
else:
swap(segments[l], segments[r])
inc l
dec r
sortSegments(segments, inl, r)
sortSegments(segments, l, inr)
proc sortSweepLines(segments: var seq[SweepLine], inl, inr: int) =
## Quicksort + insertion sort, in-place and faster than standard lib sort.
proc avg(line: SweepLine): float32 {.inline.} =
(line.tox + line.atx) / 2.float32
let n = inr - inl + 1
if n < 32: # Use insertion sort for the rest
for i in inl + 1 .. inr:
var
j = i - 1
k = i
while j >= 0 and segments[j].avg > segments[k].avg:
swap(segments[j + 1], segments[j])
dec j
dec k
return
var
l = inl
r = inr
let p = segments[l + n div 2].avg
while l <= r:
if segments[l].avg < p:
inc l
elif segments[r].avg > p:
dec r
else:
swap(segments[l], segments[r])
inc l
dec r
sortSweepLines(segments, inl, r)
sortSweepLines(segments, l, inr)
proc fillShapes(
image: Image,
shapes: seq[seq[Vec2]],
color: SomeColor,
windingRule: WindingRule,
blendMode: BlendMode
) =
let rgbx = color.rgbx
var segments = shapes.shapesToSegments()
let
bounds = computeBounds(segments).snapToPixels()
startX = max(0, bounds.x.int)
if segments.len == 0 or bounds.w.int == 0 or bounds.h.int == 0:
return
# const q = 1/10
# for i in 0 ..< segments.len:
# segments[i][0].at.x = quantize(segments[i][0].at.x, q)
# segments[i][0].at.y = quantize(segments[i][0].at.y, q)
# segments[i][0].to.x = quantize(segments[i][0].to.x, q)
# segments[i][0].to.y = quantize(segments[i][0].to.y, q)
# Create sorted segments.
segments.sortSegments(0, segments.high)
# Compute cut lines
var cutLines: seq[float32]
for s in segments:
cutLines.binaryInsert(s[0].at.y)
cutLines.binaryInsert(s[0].to.y)
var
# Dont add bottom cutLine.
sweeps = newSeq[seq[SweepLine]](cutLines.len - 1)
lastSeg = 0
i = 0
while i < sweeps.len:
if lastSeg < segments.len:
while segments[lastSeg][0].at.y == cutLines[i]:
let s = segments[lastSeg]
if s[0].to.y != cutLines[i + 1]:
var atx: float32
var seg = s[0]
for j in i ..< sweeps.len:
let y = cutLines[j + 1]
if intersectsYLine(y, seg, atx):
sweeps[j].add(toLine((segment(seg.at, vec2(atx, y)), s[1])))
seg = segment(vec2(atx, y), seg.to)
else:
if seg.at.y != seg.to.y:
sweeps[j].add(toLine(s))
break
else:
sweeps[i].add(toLine(s))
inc lastSeg
if lastSeg >= segments.len:
break
inc i
# i = 0
# while i < sweeps.len:
# # TODO: Maybe finds all cuts first, add them to array, cut all lines at once.
# var crossCuts: seq[float32]
# # echo i, " cut?"
# for aIndex in 0 ..< sweeps[i].len:
# let a = sweeps[i][aIndex]
# # echo i, ":", sweeps.len, ":", cutLines.len
# let aSeg = segment(vec2(a.atx, cutLines[i]), vec2(a.tox, cutLines[i+1]))
# for bIndex in aIndex + 1 ..< sweeps[i].len:
# let b = sweeps[i][bIndex]
# let bSeg = segment(vec2(b.atx, cutLines[i]), vec2(b.tox, cutLines[i+1]))
# var at: Vec2
# if intersectsInner(aSeg, bSeg, at):
# crossCuts.binaryInsert(at.y)
# if crossCuts.len > 0:
# var
# thisSweep = sweeps[i]
# yTop = cutLines[i]
# yBottom = cutLines[i + 1]
# sweeps[i].setLen(0)
# for k in crossCuts:
# let prevLen = cutLines.len
# cutLines.binaryInsert(k)
# if prevLen != cutLines.len:
# sweeps.insert(newSeq[SweepLine](), i + 1)
# for a in thisSweep:
# var seg = segment(vec2(a.atx, yTop), vec2(a.tox, yBottom))
# var at: Vec2
# for j, cutterLine in crossCuts:
# if intersects(line(vec2(0, cutterLine), vec2(1, cutterLine)), seg, at):
# sweeps[i+j].add(toLine((segment(seg.at, at), a.winding)))
# seg = segment(at, seg.to)
# sweeps[i+crossCuts.len].add(toLine((seg, a.winding)))
# i += crossCuts.len
# inc i
i = 0
while i < sweeps.len:
# Sort the sweep by X
sweeps[i].sortSweepLines(0, sweeps[i].high)
# Do winding order
var
pen = 0
prevFill = false
j = 0
while j < sweeps[i].len:
let a = sweeps[i][j]
if a.winding == 1:
inc pen
if a.winding == -1:
dec pen
let thisFill = shouldFill(windingRule, pen)
if prevFill == thisFill:
# Remove this sweep line.
sweeps[i].delete(j)
continue
prevFill = thisFill
inc j
inc i
# Used to debug sweeps:
# for s in 0 ..< sweeps.len:
# let
# y1 = cutLines[s]
# echo "M -100 ", y1
# echo "L 300 ", y1
# for line in sweeps[s]:
# let
# nw = vec2(line.atx, cutLines[s])
# sw = vec2(line.tox, cutLines[s + 1])
# echo "M ", nw.x, " ", nw.y
# echo "L ", sw.x, " ", sw.y
proc computeCoverage(
coverages: var seq[uint16],
y: int,
startX: int,
cutLines: seq[float32],
currCutLine: int,
sweep: seq[SweepLine]
) =
if cutLines[currCutLine + 1] - cutLines[currCutLine] < 1/256:
# TODO some thing about micro sweeps
return
let
sweepHeight = cutLines[currCutLine + 1] - cutLines[currCutLine]
yFracTop = ((y.float32 - cutLines[currCutLine]) / sweepHeight).clamp(0, 1)
yFracBottom = ((y.float32 + 1 - cutLines[currCutLine]) /
sweepHeight).clamp(0, 1)
var i = 0
while i < sweep.len:
let
nwX = mix(sweep[i+0].atx, sweep[i+0].tox, yFracTop)
neX = mix(sweep[i+1].atx, sweep[i+1].tox, yFracTop)
swX = mix(sweep[i+0].atx, sweep[i+0].tox, yFracBottom)
seX = mix(sweep[i+1].atx, sweep[i+1].tox, yFracBottom)
minWi = min(nwX, swX).int #.clamp(startX, coverages.len + startX)
maxWi = max(nwX, swX).ceil.int #.clamp(startX, coverages.len + startX)
minEi = min(neX, seX).int #.clamp(startX, coverages.len + startX)
maxEi = max(neX, seX).ceil.int #.clamp(startX, coverages.len + startX)
let
nw = vec2(sweep[i+0].atx, cutLines[currCutLine])
sw = vec2(sweep[i+0].tox, cutLines[currCutLine + 1])
f16 = (256 * 256 - 1).float32
for x in minWi ..< maxWi:
var area = pixelCover(
nw - vec2(x.float32, y.float32),
sw - vec2(x.float32, y.float32)
)
coverages[x - startX] += (area * f16).uint16
let x = maxWi
var midArea = pixelCover(
nw - vec2(x.float32, y.float32),
sw - vec2(x.float32, y.float32)
)
for x in maxWi ..< maxEi:
coverages[x - startX] += (midArea * f16).uint16
let
ne = vec2(sweep[i+1].atx, cutLines[currCutLine])
se = vec2(sweep[i+1].tox, cutLines[currCutLine + 1])
for x in minEi ..< maxEi:
var area = pixelCover(
ne - vec2(x.float32, y.float32),
se - vec2(x.float32, y.float32)
)
coverages[x - startX] -= (area * f16).uint16
i += 2
var
currCutLine = 0
coverages16 = newSeq[uint16](bounds.w.int)
coverages8 = newSeq[uint8](bounds.w.int)
for scanLine in max(cutLines[0].int, 0) ..< min(cutLines[^1].ceil.int, image.height):
zeroMem(coverages16[0].addr, coverages16.len * 2)
coverages16.computeCoverage(
scanLine, startX, cutLines, currCutLine, sweeps[currCutLine])
while cutLines[currCutLine + 1] < scanLine.float + 1.0:
inc currCutLine
if currCutLine == sweeps.len:
break
coverages16.computeCoverage(
scanLine, startX, cutLines, currCutLine, sweeps[currCutLine])
for i in 0 ..< coverages16.len:
coverages8[i] = (coverages16[i] shr 8).uint8
image.fillCoverage(
rgbx,
startX = startX,
y = scanLine,
coverages8,
blendMode
)
else: