diff --git a/src/pixie/images.nim b/src/pixie/images.nim
index ebc2c2d..cd838b8 100644
--- a/src/pixie/images.nim
+++ b/src/pixie/images.nim
@@ -1,7 +1,10 @@
-import blends, bumpy, chroma, common, masks, pixie/internal, vmath
+import blends, bumpy, chroma, common, internal, masks, vmath
 
-when defined(amd64) and allowSimd:
-  import nimsimd/sse2, runtimechecked/avx2
+when allowSimd:
+  import simd
+
+  when defined(amd64):
+    import nimsimd/sse2
 
 const h = 0.5.float32
 
@@ -28,21 +31,18 @@ proc newImage*(width, height: int): Image {.raises: [PixieError].} =
 
 proc newImage*(mask: Mask): Image {.raises: [PixieError].} =
   result = newImage(mask.width, mask.height)
-  var i: int
-  when defined(amd64) and allowSimd:
-    for _ in 0 ..< mask.data.len div 16:
-      var alphas = mm_loadu_si128(mask.data[i].addr)
-      for j in 0 ..< 4:
-        var unpacked = unpackAlphaValues(alphas)
-        unpacked = mm_or_si128(unpacked, mm_srli_epi32(unpacked, 8))
-        unpacked = mm_or_si128(unpacked, mm_srli_epi32(unpacked, 16))
-        mm_storeu_si128(result.data[i + j * 4].addr, unpacked)
-        alphas = mm_srli_si128(alphas, 4)
-      i += 16
 
-  for j in i ..< mask.data.len:
-    let v = mask.data[j]
-    result.data[j] = rgbx(v, v, v, v)
+  when allowSimd and compiles(newImageFromMaskSimd):
+    newImageFromMaskSimd(
+      cast[ptr UncheckedArray[ColorRGBX]](result.data[0].addr),
+      cast[ptr UncheckedArray[uint8]](mask.data[0].addr),
+      mask.data.len
+    )
+    return
+
+  for i in 0 ..< mask.data.len:
+    let v = mask.data[i]
+    result.data[i] = rgbx(v, v, v, v)
 
 proc copy*(image: Image): Image {.raises: [PixieError].} =
   ## Copies the image data into a new image.
@@ -101,83 +101,30 @@ proc fill*(image: Image, color: SomeColor) {.inline, raises: [].} =
 
 proc isOneColor*(image: Image): bool {.raises: [].} =
   ## Checks if the entire image is the same color.
-  when defined(amd64) and allowSimd:
-    if cpuHasAvx2:
-      return isOneColorAvx2(image.data, 0, image.data.len)
+  when allowSimd and compiles(isOneColorSimd):
+    return isOneColorSimd(
+      cast[ptr UncheckedArray[ColorRGBX]](image.data[0].addr),
+      image.data.len
+    )
 
   result = true
 
-  let color = image.data[0]
-
-  var i: int
-  when defined(amd64) and allowSimd:
-    # Align to 16 bytes
-    var p = cast[uint](image.data[i].addr)
-    while i < image.data.len and (p and 15) != 0:
-      if image.data[i] != color:
-        return false
-      inc i
-      p += 4
-
-    let
-      colorVec = mm_set1_epi32(cast[int32](color))
-      iterations = (image.data.len - i) div 16
-    for _ in 0 ..< iterations:
-      let
-        values0 = mm_load_si128(cast[pointer](p))
-        values1 = mm_load_si128(cast[pointer](p + 16))
-        values2 = mm_load_si128(cast[pointer](p + 32))
-        values3 = mm_load_si128(cast[pointer](p + 48))
-        eq0 = mm_cmpeq_epi8(values0, colorVec)
-        eq1 = mm_cmpeq_epi8(values1, colorVec)
-        eq2 = mm_cmpeq_epi8(values2, colorVec)
-        eq3 = mm_cmpeq_epi8(values3, colorVec)
-        eq0123 = mm_and_si128(mm_and_si128(eq0, eq1), mm_and_si128(eq2, eq3))
-      if mm_movemask_epi8(eq0123) != 0xffff:
-        return false
-      p += 64
-    i += 16 * iterations
-
-  for i in i ..< image.data.len:
-    if image.data[i] != color:
+  let color = cast[uint32](image.data[0])
+  for i in 0 ..< image.data.len:
+    if cast[uint32](image.data[i]) != color:
       return false
 
 proc isTransparent*(image: Image): bool {.raises: [].} =
   ## Checks if this image is fully transparent or not.
-  when defined(amd64) and allowSimd:
-    if cpuHasAvx2:
-      return isTransparentAvx2(image.data, 0, image.data.len)
+  when allowSimd and compiles(isTransparentSimd):
+    return isTransparentSimd(
+      cast[ptr UncheckedArray[ColorRGBX]](image.data[0].addr),
+      image.data.len
+    )
 
   result = true
 
-  var i: int
-  when defined(amd64) and allowSimd:
-    # Align to 16 bytes
-    var p = cast[uint](image.data[i].addr)
-    while i < image.data.len and (p and 15) != 0:
-      if image.data[i].a != 0:
-        return false
-      inc i
-      p += 4
-
-    let
-      vecZero = mm_setzero_si128()
-      iterations = (image.data.len - i) div 16
-    for _ in 0 ..< iterations:
-      let
-        values0 = mm_load_si128(cast[pointer](p))
-        values1 = mm_load_si128(cast[pointer](p + 16))
-        values2 = mm_load_si128(cast[pointer](p + 32))
-        values3 = mm_load_si128(cast[pointer](p + 48))
-        values01 = mm_or_si128(values0, values1)
-        values23 = mm_or_si128(values2, values3)
-        values0123 = mm_or_si128(values01, values23)
-      if mm_movemask_epi8(mm_cmpeq_epi8(values0123, vecZero)) != 0xffff:
-        return false
-      p += 64
-    i += 16 * iterations
-
-  for i in i ..< image.data.len:
+  for i in 0 ..< image.data.len:
     if image.data[i].a != 0:
       return false
 
@@ -410,89 +357,48 @@ 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.
-  var i: int
-  when defined(amd64) and allowSimd:
-    let vec255 = mm_set1_epi8(cast[int8](255))
-    for _ in 0 ..< image.data.len div 16:
-      let
-        a = mm_loadu_si128(image.data[i + 0].addr)
-        b = mm_loadu_si128(image.data[i + 4].addr)
-        c = mm_loadu_si128(image.data[i + 8].addr)
-        d = mm_loadu_si128(image.data[i + 12].addr)
-      mm_storeu_si128(image.data[i + 0].addr, mm_sub_epi8(vec255, a))
-      mm_storeu_si128(image.data[i + 4].addr, mm_sub_epi8(vec255, b))
-      mm_storeu_si128(image.data[i + 8].addr, mm_sub_epi8(vec255, c))
-      mm_storeu_si128(image.data[i + 12].addr, mm_sub_epi8(vec255, d))
-      i += 16
+  when allowSimd and compiles(invertImageSimd):
+    invertImageSimd(
+      cast[ptr UncheckedArray[ColorRGBX]](image.data[0].addr),
+      image.data.len
+    )
+    return
 
-  for j in i ..< image.data.len:
-    var rgbx = image.data[j]
+  for i in 0 ..< image.data.len:
+    var rgbx = image.data[i]
     rgbx.r = 255 - rgbx.r
     rgbx.g = 255 - rgbx.g
     rgbx.b = 255 - rgbx.b
     rgbx.a = 255 - rgbx.a
-    image.data[j] = rgbx
+    image.data[i] = rgbx
 
   # Inverting rgbx(50, 100, 150, 200) becomes rgbx(205, 155, 105, 55). This
   # is not a valid premultiplied alpha color.
@@ -564,22 +470,16 @@ proc newMask*(image: Image): Mask {.raises: [PixieError].} =
   ## Returns a new mask using the alpha values of the image.
   result = newMask(image.width, image.height)
 
-  var i: int
-  when defined(amd64) and allowSimd:
-    for _ in 0 ..< image.data.len div 16:
-      let
-        a = mm_loadu_si128(image.data[i + 0].addr)
-        b = mm_loadu_si128(image.data[i + 4].addr)
-        c = mm_loadu_si128(image.data[i + 8].addr)
-        d = mm_loadu_si128(image.data[i + 12].addr)
-      mm_storeu_si128(
-        result.data[i].addr,
-        pack4xAlphaValues(a, b, c, d)
-      )
-      i += 16
+  when allowSimd and compiles(newMaskFromImageSimd):
+    newMaskFromImageSimd(
+      cast[ptr UncheckedArray[uint8]](result.data[0].addr),
+      cast[ptr UncheckedArray[ColorRGBX]](image.data[0].addr),
+      image.data.len
+    )
+    return
 
-  for j in i ..< image.data.len:
-    result.data[j] = image.data[j].a
+  for i in 0 ..< image.data.len:
+    result.data[i] = image.data[i].a
 
 proc getRgbaSmooth*(
   image: Image, x, y: float32, wrapped = false
diff --git a/src/pixie/internal.nim b/src/pixie/internal.nim
index cbeb522..2524847 100644
--- a/src/pixie/internal.nim
+++ b/src/pixie/internal.nim
@@ -2,11 +2,11 @@ import bumpy, chroma, common, system/memory, vmath
 
 const allowSimd* = not defined(pixieNoSimd) and not defined(tcc)
 
-when defined(amd64) and allowSimd:
-  import nimsimd/runtimecheck, nimsimd/sse2, runtimechecked/avx, runtimechecked/avx2
-  let
-    cpuHasAvx* = checkInstructionSets({AVX})
-    cpuHasAvx2* = checkInstructionSets({AVX, AVX2})
+when allowSimd:
+  import simd
+
+  when defined(amd64):
+    import nimsimd/sse2
 
 template currentExceptionAsPixieError*(): untyped =
   ## Gets the current exception and returns it as a PixieError with stack trace.
@@ -81,45 +81,20 @@ proc fillUnsafe*(
   ## continuing for len indices.
   let rgbx = color.asRgbx()
 
-  # If we can use AVX, do so
-  when defined(amd64) and allowSimd:
-    if cpuHasAvx and len >= 64:
-      fillUnsafeAvx(data, rgbx, start, len)
-      return
+  when allowSimd and compiles(fillUnsafeSimd):
+    fillUnsafeSimd(
+      cast[ptr UncheckedArray[ColorRGBX]](data[start].addr),
+      len,
+      rgbx
+    )
+    return
 
   # Use memset when every byte has the same value
   if rgbx.r == rgbx.g and rgbx.r == rgbx.b and rgbx.r == rgbx.a:
     nimSetMem(data[start].addr, rgbx.r.cint, len * 4)
   else:
-    var i = start
-    when defined(amd64) and allowSimd:
-      # Align to 16 bytes
-      var p = cast[uint](data[i].addr)
-      while i < (start + len) and (p and 15) != 0:
-        data[i] = rgbx
-        inc i
-        p += 4
-      # When supported, SIMD fill until we run out of room
-      let
-        colorVec = mm_set1_epi32(cast[int32](rgbx))
-        iterations = (start + len - i) div 8
-      for _ in 0 ..< iterations:
-        mm_store_si128(cast[pointer](p), colorVec)
-        mm_store_si128(cast[pointer](p + 16), colorVec)
-        p += 32
-      i += iterations * 8
-    else:
-      when sizeof(int) == 8:
-        # Fill 8 bytes at a time when possible
-        var
-          u32 = cast[uint32](rgbx)
-          u64 = cast[uint64]([u32, u32])
-        for _ in 0 ..< len div 2:
-          copyMem(data[i].addr, u64.addr, 8)
-          i += 2
-    # Fill whatever is left the slow way
-    for i in i ..< start + len:
-      data[i] = rgbx
+    for color in data.mitems:
+      color = rgbx
 
 const straightAlphaTable = block:
   var table: array[256, array[256, uint8]]
@@ -141,39 +116,14 @@ proc toStraightAlpha*(data: var seq[ColorRGBA | ColorRGBX]) {.raises: [].} =
 
 proc toPremultipliedAlpha*(data: var seq[ColorRGBA | ColorRGBX]) {.raises: [].} =
   ## Converts an image to premultiplied alpha from straight alpha.
-  var i: int
-  when defined(amd64) and allowSimd:
-    if cpuHasAvx2:
-      i = toPremultipliedAlphaAvx2(data)
-    else:
-      let
-        alphaMask = mm_set1_epi32(cast[int32](0xff000000))
-        oddMask = mm_set1_epi16(cast[int16](0xff00))
-        div255 = mm_set1_epi16(cast[int16](0x8081))
-      for _ in 0 ..< data.len div 4:
-        let
-          values = mm_loadu_si128(data[i].addr)
-          alpha = mm_and_si128(values, alphaMask)
-          eq = mm_cmpeq_epi8(values, alphaMask)
-        if (mm_movemask_epi8(eq) and 0x00008888) != 0x00008888:
-          let
-            evenMultiplier = mm_or_si128(alpha, mm_srli_epi32(alpha, 16))
-            oddMultiplier = mm_or_si128(evenMultiplier, alphaMask)
-          var
-            colorsEven = mm_slli_epi16(values, 8)
-            colorsOdd = mm_and_si128(values, oddMask)
-          colorsEven = mm_mulhi_epu16(colorsEven, evenMultiplier)
-          colorsOdd = mm_mulhi_epu16(colorsOdd, oddMultiplier)
-          colorsEven = mm_srli_epi16(mm_mulhi_epu16(colorsEven, div255), 7)
-          colorsOdd = mm_srli_epi16(mm_mulhi_epu16(colorsOdd, div255), 7)
-          mm_storeu_si128(
-            data[i].addr,
-            mm_or_si128(colorsEven, mm_slli_epi16(colorsOdd, 8))
-          )
-        i += 4
+  when allowSimd and compiles(toPremultipliedAlphaSimd):
+    toPremultipliedAlphaSimd(
+      cast[ptr UncheckedArray[uint32]](data[0].addr),
+      data.len
+    )
+    return
 
-  # Convert whatever is left
-  for i in i ..< data.len:
+  for i in 0 ..< data.len:
     var c = data[i]
     if c.a != 255:
       c.r = ((c.r.uint32 * c.a) div 255).uint8
@@ -182,41 +132,15 @@ proc toPremultipliedAlpha*(data: var seq[ColorRGBA | ColorRGBX]) {.raises: [].}
       data[i] = c
 
 proc isOpaque*(data: var seq[ColorRGBX], start, len: int): bool =
-  when defined(amd64) and allowSimd:
-    if cpuHasAvx2 and len >= 64:
-      return isOpaqueAvx2(data, start, len)
+  when allowSimd and compiles(isOpaqueSimd):
+    return isOpaqueSimd(
+      cast[ptr UncheckedArray[ColorRGBX]](data[start].addr),
+      len
+    )
 
   result = true
 
-  var i = start
-  when defined(amd64) and allowSimd:
-    # Align to 16 bytes
-    var p = cast[uint](data[i].addr)
-    while i < (start + len) and (p and 15) != 0:
-      if data[i].a != 255:
-        return false
-      inc i
-      p += 4
-
-    let
-      vec255 = mm_set1_epi8(255)
-      iterations = (start + len - i) div 16
-    for _ in 0 ..< iterations:
-      let
-        values0 = mm_load_si128(cast[pointer](p))
-        values1 = mm_load_si128(cast[pointer](p + 16))
-        values2 = mm_load_si128(cast[pointer](p + 32))
-        values3 = mm_load_si128(cast[pointer](p + 48))
-        values01 = mm_and_si128(values0, values1)
-        values23 = mm_and_si128(values2, values3)
-        values0123 = mm_and_si128(values01, values23)
-        eq = mm_cmpeq_epi8(values0123, vec255)
-      if (mm_movemask_epi8(eq) and 0x00008888) != 0x00008888:
-        return false
-      p += 64
-    i += 16 * iterations
-
-  for i in i ..< start + len:
+  for i in start ..< start + len:
     if data[i].a != 255:
       return false
 
@@ -228,24 +152,7 @@ when defined(amd64) and allowSimd:
     finalColor = mm_packus_epi16(finalColor, mm_setzero_si128())
     cast[ColorRGBX](mm_cvtsi128_si32(finalColor))
 
-  proc packAlphaValues(v: M128i): M128i {.inline, raises: [].} =
-    ## Shuffle the alpha values for these 4 colors to the first 4 bytes
-    result = mm_srli_epi32(v, 24)
-    result = mm_packus_epi16(result, mm_setzero_si128())
-    result = mm_packus_epi16(result, mm_setzero_si128())
-
-  proc pack4xAlphaValues*(i, j, k, l: M128i): M128i {.inline, raises: [].} =
-    let
-      i = packAlphaValues(i)
-      j = mm_slli_si128(packAlphaValues(j), 4)
-      k = mm_slli_si128(packAlphaValues(k), 8)
-      l = mm_slli_si128(packAlphaValues(l), 12)
-    mm_or_si128(mm_or_si128(i, j), mm_or_si128(k, l))
-
-  proc unpackAlphaValues*(v: M128i): M128i {.inline, raises: [].} =
-    ## Unpack the first 32 bits into 4 rgba(0, 0, 0, value)
-    result = mm_unpacklo_epi8(mm_setzero_si128(), v)
-    result = mm_unpacklo_epi8(mm_setzero_si128(), result)
+  export pack4xAlphaValues, unpackAlphaValues
 
 when defined(release):
   {.pop.}
diff --git a/src/pixie/masks.nim b/src/pixie/masks.nim
index 7644bba..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.
@@ -213,17 +234,15 @@ proc getValueSmooth*(mask: Mask, x, y: float32): uint8 {.raises: [].} =
 
 proc invert*(mask: Mask) {.raises: [].} =
   ## Inverts all of the values - creates a negative of the mask.
-  var i: int
-  when defined(amd64) and allowSimd:
-    let vec255 = mm_set1_epi8(255)
-    for _ in 0 ..< mask.data.len div 16:
-      var values = mm_loadu_si128(mask.data[i].addr)
-      values = mm_sub_epi8(vec255, values)
-      mm_storeu_si128(mask.data[i].addr, values)
-      i += 16
+  when allowSimd and compiles(invertImageSimd):
+    invertMaskSimd(
+      cast[ptr UncheckedArray[uint8]](mask.data[0].addr),
+      mask.data.len
+    )
+    return
 
-  for j in i ..< mask.data.len:
-    mask.data[j] = 255 - mask.data[j]
+  for i in 0 ..< mask.data.len:
+    mask.data[i] = 255 - mask.data[i]
 
 proc spread*(mask: Mask, spread: float32) {.raises: [PixieError].} =
   ## Grows the mask by spread.
@@ -288,21 +307,16 @@ proc spread*(mask: Mask, spread: float32) {.raises: [PixieError].} =
 
 proc ceil*(mask: Mask) {.raises: [].} =
   ## A value of 0 stays 0. Anything else turns into 255.
-  var i: int
-  when defined(amd64) and allowSimd:
-    let
-      zeroVec = mm_setzero_si128()
-      vec255 = mm_set1_epi8(255)
-    for _ in 0 ..< mask.data.len div 16:
-      var values = mm_loadu_si128(mask.data[i].addr)
-      values = mm_cmpeq_epi8(values, zeroVec)
-      values = mm_andnot_si128(values, vec255)
-      mm_storeu_si128(mask.data[i].addr, values)
-      i += 16
+  when allowSimd and compiles(invertImageSimd):
+    ceilMaskSimd(
+      cast[ptr UncheckedArray[uint8]](mask.data[0].addr),
+      mask.data.len
+    )
+    return
 
-  for j in i ..< mask.data.len:
-    if mask.data[j] != 0:
-      mask.data[j] = 255
+  for i in 0 ..< mask.data.len:
+    if mask.data[i] != 0:
+      mask.data[i] = 255
 
 proc blur*(mask: Mask, radius: float32, outOfBounds: uint8 = 0) {.raises: [PixieError].} =
   ## Applies Gaussian blur to the image given a radius.
diff --git a/src/pixie/paths.nim b/src/pixie/paths.nim
index ef0d6e2..4cb2fa5 100644
--- a/src/pixie/paths.nim
+++ b/src/pixie/paths.nim
@@ -1823,7 +1823,7 @@ proc fillHits(
 
 proc fillShapes(
   image: Image,
-  shapes: seq[Polygon],
+  shapes: var seq[Polygon],
   color: SomeColor,
   windingRule: WindingRule,
   blendMode: BlendMode
@@ -1852,8 +1852,10 @@ proc fillShapes(
   var
     partitions = partitionSegments(segments, startY, pathHeight - startY)
     partitionIndex: int
+    entryIndices = newSeq[int](partitions.maxEntryCount)
+    numEntryIndices: int
     coverages = newSeq[uint8](pathWidth)
-    hits = newSeq[(Fixed32, int16)](partitions.maxEntryCount)
+    hits = newSeq[(Fixed32, int16)](entryIndices.len)
     numHits: int
     aa: bool
 
@@ -1895,13 +1897,13 @@ proc fillShapes(
         y += partitionHeight
         continue
 
-    var
-      allEntriesInScanlineSpanIt = true
-      tmp: int
-      entryIndices: array[2, int]
+    var allEntriesInScanlineSpanIt = true
+    numEntryIndices = 0
+
     if partitions[partitionIndex].twoNonintersectingSpanningSegments:
-      tmp = 2
-      entryIndices = [0, 1]
+      numEntryIndices = 2
+      entryIndices[0] = 0
+      entryIndices[1] = 1
     else:
       for i in 0 ..< partitions[partitionIndex].entries.len:
         if partitions[partitionIndex].entries[i].segment.to.y < y.float32 or
@@ -1911,14 +1913,10 @@ proc fillShapes(
           partitions[partitionIndex].entries[i].segment.to.y < (y + 1).float32:
           allEntriesInScanlineSpanIt = false
           break
-        if tmp < 2:
-          entryIndices[tmp] = i
-          inc tmp
-        else:
-          tmp = 0
-          break
+        entryIndices[numEntryIndices] = i
+        inc numEntryIndices
 
-    if allEntriesInScanlineSpanIt and tmp == 2:
+    if allEntriesInScanlineSpanIt and numEntryIndices == 2:
       var
         left = partitions[partitionIndex].entries[entryIndices[0]]
         right = partitions[partitionIndex].entries[entryIndices[1]]
diff --git a/src/pixie/runtimechecked/avx.nim b/src/pixie/runtimechecked/avx.nim
index 2a3b9d2..cb6d8e0 100644
--- a/src/pixie/runtimechecked/avx.nim
+++ b/src/pixie/runtimechecked/avx.nim
@@ -7,28 +7,23 @@ when defined(release):
   {.push checks: off.}
 
 proc fillUnsafeAvx*(
-  data: var seq[ColorRGBX],
-  rgbx: ColorRGBX,
-  start, len: int
+  data: ptr UncheckedArray[ColorRGBX],
+  len: int,
+  rgbx: ColorRGBX
 ) =
-  var
-    i = start
-    p = cast[uint](data[i].addr)
-  # Align to 32 bytes
-  while i < (start + len) and (p and 31) != 0:
+  var i: int
+  while i < len and (cast[uint](data[i].addr) and 31) != 0: # Align to 32 bytes
     data[i] = rgbx
     inc i
-    p += 4
-  # When supported, SIMD fill until we run out of room
+
   let
-    iterations = (start + len - i) div 8
+    iterations = (len - i) div 8
     colorVec = mm256_set1_epi32(cast[int32](rgbx))
   for _ in 0 ..< iterations:
-    mm256_store_si256(cast[pointer](p), colorVec)
-    p += 32
-  i += iterations * 8
+    mm256_store_si256(data[i].addr, colorVec)
+    i += 8
   # Fill whatever is left the slow way
-  for i in i ..< start + len:
+  for i in i ..< len:
     data[i] = rgbx
 
 when defined(release):
diff --git a/src/pixie/runtimechecked/avx2.nim b/src/pixie/runtimechecked/avx2.nim
index 3f4a86d..da34dd4 100644
--- a/src/pixie/runtimechecked/avx2.nim
+++ b/src/pixie/runtimechecked/avx2.nim
@@ -6,108 +6,96 @@ when defined(gcc) or defined(clang):
 when defined(release):
   {.push checks: off.}
 
-proc isOneColorAvx2*(data: var seq[ColorRGBX], start, len: int): bool =
+proc isOneColorAvx2*(data: ptr UncheckedArray[ColorRGBX], len: int): bool =
   result = true
 
   let color = data[0]
 
-  var
-    i = start
-    p = cast[uint](data[i].addr)
-  # Align to 32 bytes
-  while i < (start + len) and (p and 31) != 0:
+  var i: int
+  while i < len and (cast[uint](data[i].addr) and 31) != 0: # Align to 32 bytes
     if data[i] != color:
       return false
     inc i
-    p += 4
 
   let
     colorVec = mm256_set1_epi32(cast[int32](color))
-    iterations = (start + len - i) div 16
+    iterations = (len - i) div 16
   for _ in 0 ..< iterations:
     let
-      values0 = mm256_load_si256(cast[pointer](p))
-      values1 = mm256_load_si256(cast[pointer](p + 32))
+      values0 = mm256_load_si256(data[i].addr)
+      values1 = mm256_load_si256(data[i + 8].addr)
       eq0 = mm256_cmpeq_epi8(values0, colorVec)
       eq1 = mm256_cmpeq_epi8(values1, colorVec)
       eq01 = mm256_and_si256(eq0, eq1)
     if mm256_movemask_epi8(eq01) != cast[int32](0xffffffff):
       return false
-    p += 64
-  i += 16 * iterations
+    i += 16
 
-  for i in i ..< start + len:
+  for i in i ..< len:
     if data[i] != color:
       return false
 
-proc isTransparentAvx2*(data: var seq[ColorRGBX], start, len: int): bool =
+proc isTransparentAvx2*(data: ptr UncheckedArray[ColorRGBX], len: int): bool =
   result = true
 
-  var
-    i = start
-    p = cast[uint](data[i].addr)
-  # Align to 32 bytes
-  while i < (start + len) and (p and 31) != 0:
+  var i: int
+  while i < len and (cast[uint](data[i].addr) and 31) != 0: # Align to 32 bytes
     if data[i].a != 0:
       return false
     inc i
-    p += 4
 
   let
     vecZero = mm256_setzero_si256()
-    iterations = (start + len - i) div 16
+    iterations = (len - i) div 16
   for _ in 0 ..< iterations:
     let
-      values0 = mm256_load_si256(cast[pointer](p))
-      values1 = mm256_load_si256(cast[pointer](p + 32))
+      values0 = mm256_load_si256(data[i].addr)
+      values1 = mm256_load_si256(data[i + 8].addr)
       values01 = mm256_or_si256(values0, values1)
       eq = mm256_cmpeq_epi8(values01, vecZero)
     if mm256_movemask_epi8(eq) != cast[int32](0xffffffff):
       return false
-    p += 64
-  i += 16 * iterations
+    i += 16
 
-  for i in i ..< start + len:
+  for i in i ..< len:
     if data[i].a != 0:
       return false
 
-proc isOpaqueAvx2*(data: var seq[ColorRGBX], start, len: int): bool =
+proc isOpaqueAvx2*(data: ptr UncheckedArray[ColorRGBX], len: int): bool =
   result = true
 
-  var
-    i = start
-    p = cast[uint](data[i].addr)
-  # Align to 32 bytes
-  while i < (start + len) and (p and 31) != 0:
+  var i: int
+  while i < len and (cast[uint](data[i].addr) and 31) != 0: # Align to 32 bytes
     if data[i].a != 255:
       return false
     inc i
-    p += 4
 
   let
     vec255 = mm256_set1_epi8(255)
-    iterations = (start + len - i) div 16
+    iterations = (len - i) div 16
   for _ in 0 ..< iterations:
     let
-      values0 = mm256_load_si256(cast[pointer](p))
-      values1 = mm256_load_si256(cast[pointer](p + 32))
+      values0 = mm256_load_si256(data[i].addr)
+      values1 = mm256_load_si256(data[i + 8].addr)
       values01 = mm256_and_si256(values0, values1)
       eq = mm256_cmpeq_epi8(values01, vec255)
     if (mm256_movemask_epi8(eq) and 0x88888888) != 0x88888888:
       return false
-    p += 64
-  i += 16 * iterations
+    i += 16
 
-  for i in i ..< start + len:
+  for i in i ..< len:
     if data[i].a != 255:
       return false
 
-proc toPremultipliedAlphaAvx2*(data: var seq[ColorRGBA | ColorRGBX]): int =
+proc toPremultipliedAlphaAvx2*(
+  data: ptr UncheckedArray[uint32],
+  len: int
+): int =
   let
     alphaMask = mm256_set1_epi32(cast[int32](0xff000000))
     oddMask = mm256_set1_epi16(cast[int16](0xff00))
     div255 = mm256_set1_epi16(cast[int16](0x8081))
-  for _ in 0 ..< data.len div 8:
+  for _ in 0 ..< len div 8:
     let
       values = mm256_loadu_si256(data[result].addr)
       alpha = mm256_and_si256(values, alphaMask)
diff --git a/src/pixie/simd.nim b/src/pixie/simd.nim
new file mode 100644
index 0000000..d789bdf
--- /dev/null
+++ b/src/pixie/simd.nim
@@ -0,0 +1,322 @@
+import chroma, vmath
+
+when defined(release):
+  {.push checks: off.}
+
+when defined(amd64):
+  import nimsimd/runtimecheck, nimsimd/sse2, runtimechecked/avx,
+      runtimechecked/avx2
+
+  let
+    cpuHasAvx* = checkInstructionSets({AVX})
+    cpuHasAvx2* = checkInstructionSets({AVX, AVX2})
+
+  proc packAlphaValues(v: M128i): M128i {.inline.} =
+    ## Shuffle the alpha values for these 4 colors to the first 4 bytes.
+    result = mm_srli_epi32(v, 24)
+    result = mm_packus_epi16(result, mm_setzero_si128())
+    result = mm_packus_epi16(result, mm_setzero_si128())
+
+  proc pack4xAlphaValues*(i, j, k, l: M128i): M128i {.inline.} =
+    let
+      i = packAlphaValues(i)
+      j = mm_slli_si128(packAlphaValues(j), 4)
+      k = mm_slli_si128(packAlphaValues(k), 8)
+      l = mm_slli_si128(packAlphaValues(l), 12)
+    mm_or_si128(mm_or_si128(i, j), mm_or_si128(k, l))
+
+  proc unpackAlphaValues*(v: M128i): M128i {.inline, raises: [].} =
+    ## Unpack the first 32 bits into 4 rgba(0, 0, 0, value).
+    result = mm_unpacklo_epi8(mm_setzero_si128(), v)
+    result = mm_unpacklo_epi8(mm_setzero_si128(), result)
+
+  proc fillUnsafeSimd*(
+    data: ptr UncheckedArray[ColorRGBX],
+    len: int,
+    rgbx: ColorRGBX
+  ) =
+    if cpuHasAvx and len >= 64:
+      fillUnsafeAvx(data, len, rgbx)
+    else:
+      var i: int
+      while i < len and (cast[uint](data[i].addr) and 15) != 0: # Align to 16 bytes
+        data[i] = rgbx
+        inc i
+
+      let
+        colorVec = mm_set1_epi32(cast[int32](rgbx))
+        iterations = (len - i) div 8
+      for _ in 0 ..< iterations:
+        mm_store_si128(data[i].addr, colorVec)
+        mm_store_si128(data[i + 4].addr, colorVec)
+        i += 8
+
+      for i in i ..< len:
+        data[i] = rgbx
+
+  proc isOneColorSimd*(data: ptr UncheckedArray[ColorRGBX], len: int): bool =
+    if cpuHasAvx2:
+      return isOneColorAvx2(data, len)
+
+    result = true
+
+    let color = data[0]
+
+    var i: int
+    while i < len and (cast[uint](data[i].addr) and 15) != 0: # Align to 16 bytes
+      if data[i] != color:
+        return false
+      inc i
+
+    let
+      colorVec = mm_set1_epi32(cast[int32](color))
+      iterations = (len - i) div 16
+    for _ in 0 ..< iterations:
+      let
+        values0 = mm_load_si128(data[i].addr)
+        values1 = mm_load_si128(data[i + 4].addr)
+        values2 = mm_load_si128(data[i + 8].addr)
+        values3 = mm_load_si128(data[i + 12].addr)
+        eq0 = mm_cmpeq_epi8(values0, colorVec)
+        eq1 = mm_cmpeq_epi8(values1, colorVec)
+        eq2 = mm_cmpeq_epi8(values2, colorVec)
+        eq3 = mm_cmpeq_epi8(values3, colorVec)
+        eq0123 = mm_and_si128(mm_and_si128(eq0, eq1), mm_and_si128(eq2, eq3))
+      if mm_movemask_epi8(eq0123) != 0xffff:
+        return false
+      i += 16
+
+    for i in i ..< len:
+      if data[i] != color:
+        return false
+
+  proc isTransparentSimd*(data: ptr UncheckedArray[ColorRGBX], len: int): bool =
+    if cpuHasAvx2:
+      return isTransparentAvx2(data, len)
+
+    var i: int
+    while i < len and (cast[uint](data[i].addr) and 15) != 0: # Align to 16 bytes
+      if data[i].a != 0:
+        return false
+      inc i
+
+    result = true
+
+    let
+      vecZero = mm_setzero_si128()
+      iterations = (len - i) div 16
+    for _ in 0 ..< iterations:
+      let
+        values0 = mm_load_si128(data[i].addr)
+        values1 = mm_load_si128(data[i + 4].addr)
+        values2 = mm_load_si128(data[i + 8].addr)
+        values3 = mm_load_si128(data[i + 12].addr)
+        values01 = mm_or_si128(values0, values1)
+        values23 = mm_or_si128(values2, values3)
+        values0123 = mm_or_si128(values01, values23)
+      if mm_movemask_epi8(mm_cmpeq_epi8(values0123, vecZero)) != 0xffff:
+        return false
+      i += 16
+
+    for i in i ..< len:
+      if data[i].a != 0:
+        return false
+
+  proc isOpaqueSimd*(data: ptr UncheckedArray[ColorRGBX], len: int): bool =
+    if cpuHasAvx2:
+      return isOpaqueAvx2(data, len)
+
+    result = true
+
+    var i: int
+    while i < len and (cast[uint](data[i].addr) and 15) != 0: # Align to 16 bytes
+      if data[i].a != 255:
+        return false
+      inc i
+
+    let
+      vec255 = mm_set1_epi8(255)
+      iterations = (len - i) div 16
+    for _ in 0 ..< iterations:
+      let
+        values0 = mm_load_si128(data[i].addr)
+        values1 = mm_load_si128(data[i + 4].addr)
+        values2 = mm_load_si128(data[i + 8].addr)
+        values3 = mm_load_si128(data[i + 12].addr)
+        values01 = mm_and_si128(values0, values1)
+        values23 = mm_and_si128(values2, values3)
+        values0123 = mm_and_si128(values01, values23)
+        eq = mm_cmpeq_epi8(values0123, vec255)
+      if (mm_movemask_epi8(eq) and 0x00008888) != 0x00008888:
+        return false
+      i += 16
+
+    for i in i ..< len:
+      if data[i].a != 255:
+        return false
+
+  proc toPremultipliedAlphaSimd*(data: ptr UncheckedArray[uint32], len: int) =
+    var i: int
+    if cpuHasAvx2:
+      i = toPremultipliedAlphaAvx2(data, len)
+    else:
+      let
+        alphaMask = mm_set1_epi32(cast[int32](0xff000000))
+        oddMask = mm_set1_epi16(cast[int16](0xff00))
+        div255 = mm_set1_epi16(cast[int16](0x8081))
+      for _ in 0 ..< len div 4:
+        let
+          values = mm_loadu_si128(data[i].addr)
+          alpha = mm_and_si128(values, alphaMask)
+          eq = mm_cmpeq_epi8(values, alphaMask)
+        if (mm_movemask_epi8(eq) and 0x00008888) != 0x00008888:
+          let
+            evenMultiplier = mm_or_si128(alpha, mm_srli_epi32(alpha, 16))
+            oddMultiplier = mm_or_si128(evenMultiplier, alphaMask)
+          var
+            colorsEven = mm_slli_epi16(values, 8)
+            colorsOdd = mm_and_si128(values, oddMask)
+          colorsEven = mm_mulhi_epu16(colorsEven, evenMultiplier)
+          colorsOdd = mm_mulhi_epu16(colorsOdd, oddMultiplier)
+          colorsEven = mm_srli_epi16(mm_mulhi_epu16(colorsEven, div255), 7)
+          colorsOdd = mm_srli_epi16(mm_mulhi_epu16(colorsOdd, div255), 7)
+          mm_storeu_si128(
+            data[i].addr,
+            mm_or_si128(colorsEven, mm_slli_epi16(colorsOdd, 8))
+          )
+        i += 4
+
+    for i in i ..< len:
+      var c: ColorRGBX
+      copyMem(c.addr, data[i].addr, 4)
+      c.r = ((c.r.uint32 * c.a) div 255).uint8
+      c.g = ((c.g.uint32 * c.a) div 255).uint8
+      c.b = ((c.b.uint32 * c.a) div 255).uint8
+      copyMem(data[i].addr, c.addr, 4)
+
+  proc newImageFromMaskSimd*(
+    dst: ptr UncheckedArray[ColorRGBX],
+    src: ptr UncheckedArray[uint8],
+    len: int
+  ) =
+    var i: int
+    for _ in 0 ..< len div 16:
+      var alphas = mm_loadu_si128(src[i].addr)
+      for j in 0 ..< 4:
+        var unpacked = unpackAlphaValues(alphas)
+        unpacked = mm_or_si128(unpacked, mm_srli_epi32(unpacked, 8))
+        unpacked = mm_or_si128(unpacked, mm_srli_epi32(unpacked, 16))
+        mm_storeu_si128(dst[i + j * 4].addr, unpacked)
+        alphas = mm_srli_si128(alphas, 4)
+      i += 16
+
+    for i in i ..< len:
+      let v = src[i]
+      dst[i] = rgbx(v, v, v, v)
+
+  proc newMaskFromImageSimd*(
+    dst: ptr UncheckedArray[uint8],
+    src: ptr UncheckedArray[ColorRGBX],
+    len: int
+  ) =
+    var i: int
+    for _ in 0 ..< len div 16:
+      let
+        a = mm_loadu_si128(src[i + 0].addr)
+        b = mm_loadu_si128(src[i + 4].addr)
+        c = mm_loadu_si128(src[i + 8].addr)
+        d = mm_loadu_si128(src[i + 12].addr)
+      mm_storeu_si128(
+        dst[i].addr,
+        pack4xAlphaValues(a, b, c, d)
+      )
+      i += 16
+
+    for i in i ..< len:
+      dst[i] = src[i].a
+
+  proc invertImageSimd*(data: ptr UncheckedArray[ColorRGBX], len: int) =
+    var i: int
+    let vec255 = mm_set1_epi8(cast[int8](255))
+    for _ in 0 ..< len div 16:
+      let
+        a = mm_loadu_si128(data[i + 0].addr)
+        b = mm_loadu_si128(data[i + 4].addr)
+        c = mm_loadu_si128(data[i + 8].addr)
+        d = mm_loadu_si128(data[i + 12].addr)
+      mm_storeu_si128(data[i + 0].addr, mm_sub_epi8(vec255, a))
+      mm_storeu_si128(data[i + 4].addr, mm_sub_epi8(vec255, b))
+      mm_storeu_si128(data[i + 8].addr, mm_sub_epi8(vec255, c))
+      mm_storeu_si128(data[i + 12].addr, mm_sub_epi8(vec255, d))
+      i += 16
+
+    for i in i ..< len:
+      var rgbx = data[i]
+      rgbx.r = 255 - rgbx.r
+      rgbx.g = 255 - rgbx.g
+      rgbx.b = 255 - rgbx.b
+      rgbx.a = 255 - rgbx.a
+      data[i] = rgbx
+
+    toPremultipliedAlphaSimd(cast[ptr UncheckedArray[uint32]](data), len)
+
+  proc invertMaskSimd*(data: ptr UncheckedArray[uint8], len: int) =
+    var i: int
+    let vec255 = mm_set1_epi8(255)
+    for _ in 0 ..< len div 16:
+      var values = mm_loadu_si128(data[i].addr)
+      values = mm_sub_epi8(vec255, values)
+      mm_storeu_si128(data[i].addr, values)
+      i += 16
+
+    for j in i ..< len:
+      data[j] = 255 - data[j]
+
+  proc ceilMaskSimd*(data: ptr UncheckedArray[uint8], len: int) =
+    var i: int
+    let
+      zeroVec = mm_setzero_si128()
+      vec255 = mm_set1_epi8(255)
+    for _ in 0 ..< len div 16:
+      var values = mm_loadu_si128(data[i].addr)
+      values = mm_cmpeq_epi8(values, zeroVec)
+      values = mm_andnot_si128(values, vec255)
+      mm_storeu_si128(data[i].addr, values)
+      i += 16
+
+    for i in i ..< len:
+      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.}