Merge pull request #231 from treeform/masking

Fix masking, remove Intersect Mask.

src/pixie/blends.nim

@@ -32,7 +32,6 @@ type
     bmMask         ## Special blend mode that is used for masking
     bmOverwrite    ## Special blend mode that just copies pixels
     bmSubtractMask ## Inverse mask
-    bmIntersectMask
     bmExcludeMask
 
   Blender* = proc(backdrop, source: ColorRGBX): ColorRGBX
@@ -441,9 +440,9 @@ proc blendIntersectMask(backdrop, source: ColorRGBX): ColorRGBX =
 
 proc blendExcludeMask(backdrop, source: ColorRGBX): ColorRGBX =
   let a = max(backdrop.a, source.a).uint32 - min(backdrop.a, source.a)
-  result.r = ((backdrop.r * a) div 255).uint8
-  result.g = ((backdrop.g * a) div 255).uint8
-  result.b = ((backdrop.b * a) div 255).uint8
+  result.r = ((source.r * a) div 255).uint8
+  result.g = ((source.g * a) div 255).uint8
+  result.b = ((source.b * a) div 255).uint8
   result.a = a.uint8
 
 proc blendOverwrite(backdrop, source: ColorRGBX): ColorRGBX =
@@ -477,7 +476,6 @@ proc blender*(blendMode: BlendMode): Blender =
   of bmMask: blendMask
   of bmOverwrite: blendOverwrite
   of bmSubtractMask: blendSubtractMask
-  of bmIntersectMask: blendIntersectMask
   of bmExcludeMask: blendExcludeMask
 
 proc maskNormal(backdrop, source: uint8): uint8 =
@@ -507,7 +505,6 @@ proc masker*(blendMode: BlendMode): Masker =
   of bmMask: maskMask
   of bmOverwrite: maskOverwrite
   of bmSubtractMask: maskSubtract
-  of bmIntersectMask: maskIntersect
   of bmExcludeMask: maskExclude
   else:
     raise newException(PixieError, "No masker for " & $blendMode)

src/pixie/images.nim

@@ -630,7 +630,7 @@ proc drawUber(a, b: Image | Mask, mat = mat3(), blendMode = bmNormal) =
 
   # Determine where we should start and stop drawing in the y dimension
   var yMin, yMax: int
-  if blendMode == bmIntersectMask:
+  if blendMode == bmMask:
     yMin = 0
     yMax = a.height
   else:
@@ -662,7 +662,7 @@ proc drawUber(a, b: Image | Mask, mat = mat3(), blendMode = bmNormal) =
     xMin = xMin.clamp(0, a.width)
     xMax = xMax.clamp(0, a.width)
 
-    if blendMode == bmIntersectMask:
+    if blendMode == bmMask:
       if xMin > 0:
         zeroMem(a.data[a.dataIndex(0, y)].addr, 4 * xMin)
 
@@ -780,7 +780,7 @@ proc drawUber(a, b: Image | Mask, mat = mat3(), blendMode = bmNormal) =
 
         srcPos += dx
 
-    if blendMode == bmIntersectMask:
+    if blendMode == bmMask:
       if a.width - xMax > 0:
         zeroMem(a.data[a.dataIndex(xMax, y)].addr, 4 * (a.width - xMax))
 

src/pixie/paths.nim

@@ -1226,6 +1226,14 @@ proc computeCoverages(
           for j in i ..< fillStart + fillLen:
             coverages[j] += sampleCoverage
 
+proc clearUnsafe(image: Image, startX, startY, toX, toY: int) =
+  ## From startXY to toXY, exclusive, toXY is not cleared.
+  image.data.fillUnsafe(
+    rgbx(0, 0, 0, 0),
+    image.dataIndex(startX, startY),
+    image.dataIndex(toX, toY) - image.dataIndex(startX, startY)
+  )
+
 proc fillCoverage(
   image: Image,
   rgbx: ColorRGBX,
@@ -1291,7 +1299,7 @@ proc fillCoverage(
   let blender = blendMode.blender()
   while x < image.width:
     let coverage = coverages[x]
-    if coverage != 0:
+    if coverage != 0 or blendMode == bmExcludeMask:
       if blendMode == bmNormal and coverage == 255 and rgbx.a == 255:
         # Skip blending
         image.setRgbaUnsafe(x, y, rgbx)
@@ -1304,8 +1312,13 @@ proc fillCoverage(
           source.a = ((source.a.uint32 * coverage) div 255).uint8
         let backdrop = image.getRgbaUnsafe(x, y)
         image.setRgbaUnsafe(x, y, blender(backdrop, source))
+    elif blendMode == bmMask:
+      image.setRgbaUnsafe(x, y, rgbx(0, 0, 0, 0))
     inc x
 
+  if blendMode == bmMask:
+    image.clearUnsafe(0, y, startX, y)
+
 proc fillCoverage(mask: Mask, startX, y: int, coverages: seq[uint8]) =
   var x = startX
   when defined(amd64) and not defined(pixieNoSimd):
@@ -1341,6 +1354,7 @@ proc fillHits(
   blendMode: BlendMode
 ) =
   let blender = blendMode.blender()
+  var x = 0
   for (prevAt, at, count) in hits.walk(numHits, windingRule, y, image.wh):
     let
       fillStart = prevAt.int
@@ -1349,7 +1363,7 @@ proc fillHits(
       if blendMode == bmNormal and rgbx.a == 255:
         fillUnsafe(image.data, rgbx, image.dataIndex(fillStart, y), fillLen)
       else:
-        var x = fillStart
+        x = fillStart
         when defined(amd64) and not defined(pixieNoSimd):
           if blendMode.hasSimdBlender():
             # When supported, SIMD blend as much as possible
@@ -1370,6 +1384,10 @@ proc fillHits(
           image.setRgbaUnsafe(x, y, blender(backdrop, rgbx))
           inc x
 
+  if blendMode == bmMask:
+    image.clearUnsafe(0, y, startX, y)
+    image.clearUnsafe(x, y, image.width, y)
+
 proc fillHits(
   mask: Mask,
   startX, y: int,
@@ -1438,6 +1456,10 @@ proc fillShapes(
         blendMode
       )
 
+  if blendMode == bmMask:
+    image.clearUnsafe(0, 0, 0, startY)
+    image.clearUnsafe(0, pathHeight, 0, image.height)
+
 proc fillShapes(mask: Mask, shapes: seq[seq[Vec2]], windingRule: WindingRule) =
   # Figure out the total bounds of all the shapes,
   # rasterize only within the total bounds

tests/test_paths.nim

@@ -363,3 +363,51 @@ block:
     path = parsePath("L 0 0")
   image.fill(rgba(255, 255, 255, 255))
   image.strokePath(path, rgba(0, 0, 0, 255), vec2(10, 10), 10, lcSquare, ljMiter)
+
+block:
+  let image = newImage(100, 100)
+  image.fillPath(
+    "M 10 10 H 60 V 60 H 10 z",
+    Paint(kind: pkSolid, color: rgbx(255, 0, 0, 255), blendMode: bmNormal)
+  )
+  image.fillPath(
+    "M 30 30 H 80 V 80 H 30 z",
+    Paint(kind: pkSolid, color: rgbx(0, 255, 0, 255), blendMode: bmExcludeMask)
+  )
+  image.writeFile("tests/images/paths/rectExcludeMask.png")
+
+block:
+  let image = newImage(100, 100)
+  image.fillPath(
+    "M 10.1 10.1 H 60.1 V 60.1 H 10.1 z",
+    Paint(kind: pkSolid, color: rgbx(255, 0, 0, 255), blendMode: bmNormal)
+  )
+  image.fillPath(
+    "M 30.1 30.1 H 80.1 V 80.1 H 30.1 z",
+    Paint(kind: pkSolid, color: rgbx(0, 255, 0, 255), blendMode: bmExcludeMask)
+  )
+  image.writeFile("tests/images/paths/rectExcludeMaskAA.png")
+
+block:
+  let image = newImage(100, 100)
+  image.fillPath(
+    "M 10 10 H 60 V 60 H 10 z",
+    Paint(kind: pkSolid, color: rgbx(255, 0, 0, 255), blendMode: bmNormal)
+  )
+  image.fillPath(
+    "M 30 30 H 80 V 80 H 30 z",
+    Paint(kind: pkSolid, color: rgbx(0, 255, 0, 255), blendMode: bmMask)
+  )
+  image.writeFile("tests/images/paths/rectMask.png")
+
+block:
+  let image = newImage(100, 100)
+  image.fillPath(
+    "M 10.1 10.1 H 60.1 V 60.1 H 10.1 z",
+    Paint(kind: pkSolid, color: rgbx(255, 0, 0, 255), blendMode: bmNormal)
+  )
+  image.fillPath(
+    "M 30.1 30.1 H 80.1 V 80.1 H 30.1 z",
+    Paint(kind: pkSolid, color: rgbx(0, 255, 0, 255), blendMode: bmMask)
+  )
+  image.writeFile("tests/images/paths/rectMaskAA.png")