paint has opacity

src/pixie/internal.nim

@@ -23,6 +23,18 @@ proc gaussianKernel*(radius: int): seq[uint32] =
   for i, f in floats:
     result[i] = round(f * 255 * 1024).uint32
 
+proc applyOpacity*(color: ColorRGBX, opacity: float32): ColorRGBX =
+  if opacity == 0:
+    rgbx(0, 0, 0, 0)
+  else:
+    let
+      x = round(opacity * 255).uint32
+      r = ((color.r * x) div 255).uint8
+      g = ((color.g * x) div 255).uint8
+      b = ((color.b * x) div 255).uint8
+      a = ((color.a * x) div 255).uint8
+    rgbx(r, g, b, a)
+
 proc toStraightAlpha*(data: var seq[ColorRGBA | ColorRGBX]) =
   ## Converts an image from premultiplied alpha to straight alpha.
   ## This is expensive for large images.

src/pixie/paints.nim

@@ -1,4 +1,4 @@
-import blends, chroma, common, images, vmath
+import blends, chroma, common, images, internal, options, vmath
 
 type
   PaintKind* = enum
@@ -21,6 +21,7 @@ type
       gradientHandlePositions*: seq[Vec2] ## Gradient positions (image space).
       gradientStops*: seq[ColorStop]      ## Color stops (gradient space).
     blendMode*: BlendMode                 ## Blend mode.
+    opacityOption: Option[float32]
 
   ColorStop* = object
     ## Color stop on a gradient curve.
@@ -41,37 +42,55 @@ converter parseSomePaint*(paint: SomePaint): Paint {.inline.} =
   elif type(paint) is Paint:
     paint
 
+proc opacity*(paint: Paint): float32 =
+  ## Paint opacity (applies with color or image opacity).
+  if paint.opacityOption.isSome:
+    paint.opacityOption.get()
+  else:
+    1
+
+proc `opacity=`*(paint: var Paint, opacity: float32) =
+  ## Set the paint opacity (applies with color or image opacity).
+  if opacity >= 0 and opacity <= 1:
+    paint.opacityOption = some(opacity)
+  else:
+    raise newException(PixieError, "Invalid opacity: " & $opacity)
+
 proc toLineSpace(at, to, point: Vec2): float32 {.inline.} =
   ## Convert position on to where it would fall on a line between at and to.
   let
     d = to - at
     det = d.x * d.x + d.y * d.y
-  return (d.y * (point.y - at.y) + d.x * (point.x - at.x)) / det
+  (d.y * (point.y - at.y) + d.x * (point.x - at.x)) / det
 
-proc gradientPut(image: Image, x, y: int, a: float32, stops: seq[ColorStop]) =
-  ## Put an gradient color based on the "a" - were are we related to a line.
+proc gradientPut(
+  image: Image, paint: Paint, x, y: int, t: float32, stops: seq[ColorStop]
+) =
+  ## Put an gradient color based on `t` - where are we related to a line.
   var index = -1
   for i, stop in stops:
-    if stop.position < a:
+    if stop.position < t:
       index = i
-    if stop.position > a:
+    if stop.position > t:
       break
-  var color: Color
+  var color: ColorRGBX
   if index == -1:
     # first stop solid
-    color = stops[0].color.color
+    color = stops[0].color
   elif index + 1 >= stops.len:
     # last stop solid
-    color = stops[index].color.color
+    color = stops[index].color
   else:
     let
       gs1 = stops[index]
-      gs2 = stops[index+1]
-    color = mix(
-      gs1.color.color,
-      gs2.color.color,
-      (a - gs1.position) / (gs2.position - gs1.position)
+      gs2 = stops[index + 1]
+    color = lerp(
+      gs1.color,
+      gs2.color,
+      (t - gs1.position) / (gs2.position - gs1.position)
     )
+  if paint.opacity != 0:
+    color = color.applyOpacity(paint.opacity)
   image.setRgbaUnsafe(x, y, color.rgba.rgbx())
 
 proc fillGradientLinear*(image: Image, paint: Paint) =
@@ -86,6 +105,9 @@ proc fillGradientLinear*(image: Image, paint: Paint) =
   if paint.gradientStops.len == 0:
     raise newException(PixieError, "Gradient must have at least 1 color stop")
 
+  if paint.opacity == 0:
+    return
+
   let
     at = paint.gradientHandlePositions[0]
     to = paint.gradientHandlePositions[1]
@@ -93,8 +115,8 @@ proc fillGradientLinear*(image: Image, paint: Paint) =
     for x in 0 ..< image.width:
       let
         xy = vec2(x.float32, y.float32)
-        a = toLineSpace(at, to, xy)
-      image.gradientPut(x, y, a, paint.gradientStops)
+        t = toLineSpace(at, to, xy)
+      image.gradientPut(paint, x, y, t, paint.gradientStops)
 
 proc fillGradientRadial*(image: Image, paint: Paint) =
   ## Fills a radial gradient.
@@ -108,6 +130,9 @@ proc fillGradientRadial*(image: Image, paint: Paint) =
   if paint.gradientStops.len == 0:
     raise newException(PixieError, "Gradient must have at least 1 color stop")
 
+  if paint.opacity == 0:
+    return
+
   let
     center = paint.gradientHandlePositions[0]
     edge = paint.gradientHandlePositions[1]
@@ -124,8 +149,8 @@ proc fillGradientRadial*(image: Image, paint: Paint) =
     for x in 0 ..< image.width:
       let
         xy = vec2(x.float32, y.float32)
-        b = (mat * xy).length()
-      image.gradientPut(x, y, b, paint.gradientStops)
+        t = (mat * xy).length()
+      image.gradientPut(paint, x, y, t, paint.gradientStops)
 
 proc fillGradientAngular*(image: Image, paint: Paint) =
   ## Fills an angular gradient.
@@ -139,6 +164,9 @@ proc fillGradientAngular*(image: Image, paint: Paint) =
   if paint.gradientStops.len == 0:
     raise newException(PixieError, "Gradient must have at least 1 color stop")
 
+  if paint.opacity == 0:
+    return
+
   let
     center = paint.gradientHandlePositions[0]
     edge = paint.gradientHandlePositions[1]
@@ -149,5 +177,5 @@ proc fillGradientAngular*(image: Image, paint: Paint) =
       let
         xy = vec2(x.float32, y.float32)
         angle = normalize(xy - center).angle()
-        a = (angle + gradientAngle + PI/2).fixAngle() / 2 / PI + 0.5
-      image.gradientPut(x, y, a, paint.gradientStops)
+        t = (angle + gradientAngle + PI / 2).fixAngle() / 2 / PI + 0.5
+      image.gradientPut(paint, x, y, t, paint.gradientStops)

src/pixie/paths.nim

@@ -1,5 +1,4 @@
-import blends, bumpy, chroma, common, images, masks, paints, pixie/internal,
-    strutils, vmath
+import blends, bumpy, chroma, common, images, masks, paints, internal, strutils, vmath
 
 when defined(amd64) and not defined(pixieNoSimd):
   import nimsimd/sse2
@@ -1780,11 +1779,17 @@ proc fillPath*(
   windingRule = wrNonZero
 ) =
   ## Fills a path.
+  if paint.opacity == 0:
+    return
+
   if paint.kind == pkSolid:
     if paint.color.a > 0 or paint.blendMode == bmOverwrite:
       var shapes = parseSomePath(path, true, transform.pixelScale())
       shapes.transform(transform)
-      image.fillShapes(shapes, paint.color, windingRule, paint.blendMode)
+      var color = paint.color
+      if paint.opacity != 1:
+        color = color.applyOpacity(paint.opacity)
+      image.fillShapes(shapes, color, windingRule, paint.blendMode)
     return
 
   let
@@ -1793,19 +1798,25 @@ proc fillPath*(
 
   mask.fillPath(path, transform, windingRule)
 
+  var paintOpaque = paint
+  paintOpaque.opacity = 1
+
   case paint.kind:
     of pkSolid:
       discard # Handled above
     of pkImage:
-      fill.draw(paint.image, paint.imageMat)
+      fill.draw(paintOpaque.image, paintOpaque.imageMat)
     of pkImageTiled:
-      fill.drawTiled(paint.image, paint.imageMat)
+      fill.drawTiled(paintOpaque.image, paintOpaque.imageMat)
     of pkGradientLinear:
-      fill.fillGradientLinear(paint)
+      fill.fillGradientLinear(paintOpaque)
     of pkGradientRadial:
-      fill.fillGradientRadial(paint)
+      fill.fillGradientRadial(paintOpaque)
     of pkGradientAngular:
-      fill.fillGradientAngular(paint)
+      fill.fillGradientAngular(paintOpaque)
+
+  if paint.opacity != 1:
+    mask.applyOpacity(paint.opacity)
 
   fill.draw(mask)
   image.draw(fill, blendMode = paint.blendMode)
@@ -1845,6 +1856,9 @@ proc strokePath*(
   dashes: seq[float32] = @[]
 ) =
   ## Strokes a path.
+  if paint.opacity == 0:
+    return
+
   if paint.kind == pkSolid:
     if paint.color.a > 0 or paint.blendMode == bmOverwrite:
       var strokeShapes = strokeShapes(
@@ -1856,7 +1870,10 @@ proc strokePath*(
         dashes
       )
       strokeShapes.transform(transform)
-      image.fillShapes(strokeShapes, paint.color, wrNonZero, paint.blendMode)
+      var color = paint.color
+      if paint.opacity != 1:
+        color = color.applyOpacity(paint.opacity)
+      image.fillShapes(strokeShapes, color, wrNonZero, paint.blendMode)
     return
 
   let
@@ -1873,19 +1890,25 @@ proc strokePath*(
     dashes
   )
 
+  var paintOpaque = paint
+  paintOpaque.opacity = 1
+
   case paint.kind:
     of pkSolid:
       discard # Handled above
     of pkImage:
-      fill.draw(paint.image, paint.imageMat)
+      fill.draw(paintOpaque.image, paintOpaque.imageMat)
     of pkImageTiled:
-      fill.drawTiled(paint.image, paint.imageMat)
+      fill.drawTiled(paintOpaque.image, paintOpaque.imageMat)
     of pkGradientLinear:
-      fill.fillGradientLinear(paint)
+      fill.fillGradientLinear(paintOpaque)
     of pkGradientRadial:
-      fill.fillGradientRadial(paint)
+      fill.fillGradientRadial(paintOpaque)
     of pkGradientAngular:
-      fill.fillGradientAngular(paint)
+      fill.fillGradientAngular(paintOpaque)
+
+  if paint.opacity != 1:
+    mask.applyOpacity(paint.opacity)
 
   fill.draw(mask)
   image.draw(fill, blendMode = paint.blendMode)

tests/test_paints.nim

@@ -31,6 +31,21 @@ block:
   )
   image.writeFile("tests/images/paths/paintImage.png")
 
+block:
+  var paint = Paint(
+    kind: pkImage,
+    image: decodePng(readFile("tests/images/png/baboon.png")),
+    imageMat: scale(vec2(0.2, 0.2))
+  )
+  paint.opacity = 0.5
+
+  let image = newImage(100, 100)
+  image.fillPath(
+    heartShape,
+    paint
+  )
+  image.writeFile("tests/images/paths/paintImageOpacity.png")
+
 block:
   let image = newImage(100, 100)
   image.fillPath(
@@ -43,6 +58,21 @@ block:
   )
   image.writeFile("tests/images/paths/paintImageTiled.png")
 
+block:
+  var paint = Paint(
+    kind: pkImageTiled,
+    image: decodePng(readFile("tests/images/png/baboon.png")),
+    imageMat: scale(vec2(0.02, 0.02))
+  )
+  paint.opacity = 0.5
+
+  let image = newImage(100, 100)
+  image.fillPath(
+    heartShape,
+    paint
+  )
+  image.writeFile("tests/images/paths/paintImageTiledOpacity.png")
+
 block:
   let image = newImage(100, 100)
   image.fillPath(
@@ -100,3 +130,26 @@ block:
   )
 
   image.writeFile("tests/images/paths/gradientAngular.png")
+
+block:
+  var paint = Paint(
+    kind: pkGradientAngular,
+    gradientHandlePositions: @[
+      vec2(50, 50),
+      vec2(100, 50),
+      vec2(50, 100)
+    ],
+    gradientStops: @[
+      ColorStop(color: rgba(255, 0, 0, 255), position: 0),
+      ColorStop(color: rgba(255, 0, 0, 40), position: 1.0),
+    ]
+  )
+  paint.opacity = 0.5
+
+  let image = newImage(100, 100)
+  image.fillPath(
+    heartShape,
+    paint
+  )
+
+  image.writeFile("tests/images/paths/gradientAngularOpacity.png")

tests/test_paths.nim

@@ -568,3 +568,27 @@ block:
   doAssert path.strokeOverlaps(vec2(40, 20))
   doAssert path.strokeOverlaps(vec2(19.8, 30.2))
   doAssert not path.strokeOverlaps(vec2(19.4, 30.6))
+
+block:
+  var path: Path
+  path.circle(50, 50, 30)
+
+  var paint = Paint(kind: pkSolid, color: rgba(255, 0, 255, 255))
+  paint.opacity = 0.5
+
+  let image = newImage(100, 100)
+  image.fillPath(path, paint)
+
+  image.writeFile("tests/images/paths/opacityFill.png")
+
+block:
+  var path: Path
+  path.circle(50, 50, 30)
+
+  var paint = Paint(kind: pkSolid, color: rgba(255, 0, 255, 255))
+  paint.opacity = 0.5
+
+  let image = newImage(100, 100)
+  image.strokePath(path, paint, strokeWidth = 10)
+
+  image.writeFile("tests/images/paths/opacityStroke.png")