bmMask nonsimd draw faster

experiments/benchmark_cairo_draw.nim

@@ -35,6 +35,38 @@ block:
 
   # tmp.writeFile("tmp2.png")
 
+block:
+  let
+    backdrop = imageSurfaceCreateFromPng("tests/fileformats/svg/masters/dragon2.png")
+    source = imageSurfaceCreateFromPng("tests/fileformats/svg/masters/Ghostscript_Tiger.png")
+    tmp = imageSurfaceCreate(FORMAT_ARGB32, 1568, 940)
+    ctx = tmp.create()
+
+  timeIt "cairo draw mask":
+    ctx.setSourceRgba(1, 1, 1, 1)
+    let operator = ctx.getOperator()
+    ctx.setOperator(OperatorSource)
+    ctx.paint()
+    ctx.setOperator(operator)
+
+    ctx.setSource(backdrop, 0, 0)
+    ctx.mask(source, 0, 0)
+    tmp.flush()
+
+  echo tmp.writeToPng("tmp_masked.png")
+
+block:
+  let
+    backdrop = readImage("tests/fileformats/svg/masters/dragon2.png")
+    source = readImage("tests/fileformats/svg/masters/Ghostscript_Tiger.png")
+    tmp = newImage(1568, 940)
+
+  timeIt "pixie draw mask":
+    tmp.draw(backdrop)
+    tmp.draw(source, blendMode = bmMask)
+
+  tmp.writeFile("tmp_masked2.png")
+
 block:
   let
     backdrop = imageSurfaceCreateFromPng("tests/fileformats/svg/masters/dragon2.png")

src/pixie/blends.nim

@@ -419,7 +419,7 @@ proc blendSaturation(backdrop, source: ColorRGBX): ColorRGBX =
     blended = SetLum(SetSat(backdrop, Sat(source)), Lum(backdrop))
   result = alphaFix(backdrop, source, blended).rgba.rgbx()
 
-proc blendMask(backdrop, source: ColorRGBX): ColorRGBX =
+proc blendMask*(backdrop, source: ColorRGBX): ColorRGBX =
   let k = source.a.uint32
   result.r = ((backdrop.r * k) div 255).uint8
   result.g = ((backdrop.g * k) div 255).uint8

src/pixie/images.nim

@@ -955,6 +955,30 @@ proc drawUber(
                 let backdrop = a.unsafe[x, y]
                 a.unsafe[x, y] = blendAlpha(backdrop, source)
           srcPos += dx
+      elif blendMode == bmMask:
+        for x in x ..< xMax:
+          let samplePos = ivec2((srcPos.x - h).int32, (srcPos.y - h).int32)
+          when type(a) is Image:
+            when type(b) is Image:
+              let source = b.unsafe[samplePos.x, samplePos.y]
+            else: # b is a Mask
+              let source = rgbx(0, 0, 0, b.unsafe[samplePos.x, samplePos.y])
+            if source.a == 0:
+              a.unsafe[x, y] = rgbx(0, 0, 0, 0)
+            elif source.a != 255:
+              let backdrop = a.unsafe[x, y]
+              a.unsafe[x, y] = blendMask(backdrop, source)
+          else: # a is a Mask
+            when type(b) is Image:
+              let source = b.unsafe[samplePos.x, samplePos.y].a
+            else: # b is a Mask
+              let source = b.unsafe[samplePos.x, samplePos.y]
+            if source == 0:
+              a.unsafe[x, y] = 0
+            elif source != 255:
+              let backdrop = a.unsafe[x, y]
+              a.unsafe[x, y] = blendAlpha(backdrop, source)
+          srcPos += dx
       else:
         for x in x ..< xMax:
           let samplePos = ivec2((srcPos.x - h).int32, (srcPos.y - h).int32)