diff --git a/src/pixie/images.nim b/src/pixie/images.nim
index 33119db..7e47209 100644
--- a/src/pixie/images.nim
+++ b/src/pixie/images.nim
@@ -357,64 +357,31 @@ proc magnifyBy2*(image: Image, power = 1): Image {.raises: [PixieError].} =
         result.width * 4
       )
 
-proc applyOpacity*(target: Image | Mask, opacity: float32) {.raises: [].} =
+proc applyOpacity*(image: Image, opacity: float32) {.raises: [].} =
   ## Multiplies alpha of the image by opacity.
   let opacity = round(255 * opacity).uint16
   if opacity == 255:
     return
 
   if opacity == 0:
-    when type(target) is Image:
-      target.fill(rgbx(0, 0, 0, 0))
-    else:
-      target.fill(0)
+    image.fill(rgbx(0, 0, 0, 0))
     return
 
-  var i: int
-  when defined(amd64) and allowSimd:
-    when type(target) is Image:
-      let byteLen = target.data.len * 4
-    else:
-      let byteLen = target.data.len
+  when allowSimd and compiles(applyOpacitySimd):
+    applyOpacitySimd(
+      cast[ptr UncheckedArray[uint8]](image.data[0].addr),
+      image.data.len * 4,
+      opacity
+    )
+    return
 
-    let
-      oddMask = mm_set1_epi16(cast[int16](0xff00))
-      div255 = mm_set1_epi16(cast[int16](0x8081))
-      zeroVec = mm_setzero_si128()
-      opacityVec = mm_slli_epi16(mm_set1_epi16(cast[int16](opacity)), 8)
-    for _ in 0 ..< byteLen div 16:
-      when type(target) is Image:
-        let index = i div 4
-      else:
-        let index = i
-
-      let values = mm_loadu_si128(target.data[index].addr)
-      if mm_movemask_epi8(mm_cmpeq_epi16(values, zeroVec)) != 0xffff:
-        var
-          valuesEven = mm_slli_epi16(values, 8)
-          valuesOdd = mm_and_si128(values, oddMask)
-        valuesEven = mm_mulhi_epu16(valuesEven, opacityVec)
-        valuesOdd = mm_mulhi_epu16(valuesOdd, opacityVec)
-        valuesEven = mm_srli_epi16(mm_mulhi_epu16(valuesEven, div255), 7)
-        valuesOdd = mm_srli_epi16(mm_mulhi_epu16(valuesOdd, div255), 7)
-        mm_storeu_si128(
-          target.data[index].addr,
-          mm_or_si128(valuesEven, mm_slli_epi16(valuesOdd, 8))
-        )
-
-      i += 16
-
-  when type(target) is Image:
-    for j in i div 4 ..< target.data.len:
-      var rgbx = target.data[j]
-      rgbx.r = ((rgbx.r * opacity) div 255).uint8
-      rgbx.g = ((rgbx.g * opacity) div 255).uint8
-      rgbx.b = ((rgbx.b * opacity) div 255).uint8
-      rgbx.a = ((rgbx.a * opacity) div 255).uint8
-      target.data[j] = rgbx
-  else:
-    for j in i ..< target.data.len:
-      target.data[j] = ((target.data[j] * opacity) div 255).uint8
+  for i in 0 ..< image.data.len:
+    var rgbx = image.data[i]
+    rgbx.r = ((rgbx.r * opacity) div 255).uint8
+    rgbx.g = ((rgbx.g * opacity) div 255).uint8
+    rgbx.b = ((rgbx.b * opacity) div 255).uint8
+    rgbx.a = ((rgbx.a * opacity) div 255).uint8
+    image.data[i] = rgbx
 
 proc invert*(image: Image) {.raises: [].} =
   ## Inverts all of the colors and alpha.
diff --git a/src/pixie/masks.nim b/src/pixie/masks.nim
index 7b29e09..40b2ea4 100644
--- a/src/pixie/masks.nim
+++ b/src/pixie/masks.nim
@@ -75,6 +75,10 @@ proc setValue*(mask: Mask, x, y: int, value: uint8) {.inline, raises: [].} =
   ## Sets a value at (x, y) or does nothing if outside of bounds.
   mask[x, y] = value
 
+proc fill*(mask: Mask, value: uint8) {.inline, raises: [].} =
+  ## Fills the mask with the value.
+  fillUnsafe(mask.data, value, 0, mask.data.len)
+
 proc minifyBy2*(mask: Mask, power = 1): Mask {.raises: [PixieError].} =
   ## Scales the mask down by an integer scale.
   if power < 0:
@@ -179,9 +183,26 @@ proc magnifyBy2*(mask: Mask, power = 1): Mask {.raises: [PixieError].} =
         result.width * 4
       )
 
-proc fill*(mask: Mask, value: uint8) {.inline, raises: [].} =
-  ## Fills the mask with the value.
-  fillUnsafe(mask.data, value, 0, mask.data.len)
+proc applyOpacity*(mask: Mask, opacity: float32) {.raises: [].} =
+  ## Multiplies alpha of the image by opacity.
+  let opacity = round(255 * opacity).uint16
+  if opacity == 255:
+    return
+
+  if opacity == 0:
+    mask.fill(0)
+    return
+
+  when allowSimd and compiles(applyOpacitySimd):
+    applyOpacitySimd(
+      cast[ptr UncheckedArray[uint8]](mask.data[0].addr),
+      mask.data.len,
+      opacity
+    )
+    return
+
+  for i in 0 ..< mask.data.len:
+    mask.data[i] = ((mask.data[i] * opacity) div 255).uint8
 
 proc getValueSmooth*(mask: Mask, x, y: float32): uint8 {.raises: [].} =
   ## Gets a interpolated value with float point coordinates.
diff --git a/src/pixie/simd.nim b/src/pixie/simd.nim
index 3f43755..40a17fa 100644
--- a/src/pixie/simd.nim
+++ b/src/pixie/simd.nim
@@ -1,4 +1,4 @@
-import chroma
+import chroma, vmath
 
 when defined(release):
   {.push checks: off.}
@@ -287,5 +287,35 @@ when defined(amd64):
       if data[i] != 0:
         data[i] = 255
 
+  proc applyOpacitySimd*(
+    data: ptr UncheckedArray[uint8],
+    len: int,
+    opacity: uint16
+  ) =
+    var i: int
+    let
+      oddMask = mm_set1_epi16(cast[int16](0xff00))
+      div255 = mm_set1_epi16(cast[int16](0x8081))
+      zeroVec = mm_setzero_si128()
+      opacityVec = mm_slli_epi16(mm_set1_epi16(cast[int16](opacity)), 8)
+    for _ in 0 ..< len div 16:
+      let values = mm_loadu_si128(data[i].addr)
+      if mm_movemask_epi8(mm_cmpeq_epi16(values, zeroVec)) != 0xffff:
+        var
+          valuesEven = mm_slli_epi16(values, 8)
+          valuesOdd = mm_and_si128(values, oddMask)
+        valuesEven = mm_mulhi_epu16(valuesEven, opacityVec)
+        valuesOdd = mm_mulhi_epu16(valuesOdd, opacityVec)
+        valuesEven = mm_srli_epi16(mm_mulhi_epu16(valuesEven, div255), 7)
+        valuesOdd = mm_srli_epi16(mm_mulhi_epu16(valuesOdd, div255), 7)
+        mm_storeu_si128(
+          data[i].addr,
+          mm_or_si128(valuesEven, mm_slli_epi16(valuesOdd, 8))
+        )
+      i += 16
+
+    for i in i ..< len:
+      data[i] = ((data[i] * opacity) div 255).uint8
+
 when defined(release):
   {.pop.}