diff --git a/src/pixie/blends.nim b/src/pixie/blends.nim
index 6a3d2e0..fac4e03 100644
--- a/src/pixie/blends.nim
+++ b/src/pixie/blends.nim
@@ -609,7 +609,7 @@ when defined(amd64) and not defined(pixieNoSimd):
     sourceEven = mm_srli_epi16(sourceEven, 8)
     sourceOdd = mm_srli_epi16(sourceOdd, 8)
 
-    var
+    let
       blendedEven = mm_add_epi16(sourceEven, backdropEven)
       blendedOdd = mm_add_epi16(sourceOdd, backdropOdd)
 
diff --git a/src/pixie/common.nim b/src/pixie/common.nim
index e596169..4e11656 100644
--- a/src/pixie/common.nim
+++ b/src/pixie/common.nim
@@ -3,12 +3,12 @@ import bumpy, chroma, vmath
 type
   PixieError* = object of ValueError ## Raised if an operation fails.
 
-proc lerp*(a, b: uint8, t: float32): uint8 {.inline, raises: [].} =
+proc mix*(a, b: uint8, t: float32): uint8 {.inline, raises: [].} =
   ## Linearly interpolate between a and b using t.
   let t = round(t * 255).uint32
   ((a * (255 - t) + b * t) div 255).uint8
 
-proc lerp*(a, b: ColorRGBX, t: float32): ColorRGBX {.inline, raises: [].} =
+proc mix*(a, b: ColorRGBX, t: float32): ColorRGBX {.inline, raises: [].} =
   ## Linearly interpolate between a and b using t.
   let x = round(t * 255).uint32
   result.r = ((a.r.uint32 * (255 - x) + b.r.uint32 * x) div 255).uint8
@@ -16,13 +16,6 @@ proc lerp*(a, b: ColorRGBX, t: float32): ColorRGBX {.inline, raises: [].} =
   result.b = ((a.b.uint32 * (255 - x) + b.b.uint32 * x) div 255).uint8
   result.a = ((a.a.uint32 * (255 - x) + b.a.uint32 * x) div 255).uint8
 
-proc lerp*(a, b: Color, v: float32): Color {.inline, raises: [].} =
-  ## Linearly interpolate between a and b using t.
-  result.r = lerp(a.r, b.r, v)
-  result.g = lerp(a.g, b.g, v)
-  result.b = lerp(a.b, b.b, v)
-  result.a = lerp(a.a, b.a, v)
-
 proc snapToPixels*(rect: Rect): Rect {.raises: [].} =
   let
     xMin = rect.x
diff --git a/src/pixie/fonts.nim b/src/pixie/fonts.nim
index 59687fb..f2d019a 100644
--- a/src/pixie/fonts.nim
+++ b/src/pixie/fonts.nim
@@ -478,7 +478,7 @@ proc textUber(
     for runeIndex in start .. stop:
       let position = arrangement.positions[runeIndex]
 
-      var path = font.typeface.getGlyphPath(arrangement.runes[runeIndex])
+      let path = font.typeface.getGlyphPath(arrangement.runes[runeIndex])
       path.transform(
         translate(position) *
         scale(vec2(font.scale))
diff --git a/src/pixie/images.nim b/src/pixie/images.nim
index e4e7339..aecc670 100644
--- a/src/pixie/images.nim
+++ b/src/pixie/images.nim
@@ -368,7 +368,7 @@ proc applyOpacity*(target: Image | Mask, opacity: float32) {.raises: [].} =
       else:
         let index = i
 
-      var values = mm_loadu_si128(target.data[index].addr)
+      let values = mm_loadu_si128(target.data[index].addr)
 
       let eqZero = mm_cmpeq_epi16(values, mm_setzero_si128())
       if mm_movemask_epi8(eqZero) != 0xffff:
@@ -571,14 +571,14 @@ proc getRgbaSmooth*(
 
   var topMix = x0y0
   if xFractional > 0 and x0y0 != x1y0:
-    topMix = lerp(x0y0, x1y0, xFractional)
+    topMix = mix(x0y0, x1y0, xFractional)
 
   var bottomMix = x0y1
   if xFractional > 0 and x0y1 != x1y1:
-    bottomMix = lerp(x0y1, x1y1, xFractional)
+    bottomMix = mix(x0y1, x1y1, xFractional)
 
   if yFractional != 0 and topMix != bottomMix:
-    lerp(topMix, bottomMix, yFractional)
+    mix(topMix, bottomMix, yFractional)
   else:
     topMix
 
diff --git a/src/pixie/masks.nim b/src/pixie/masks.nim
index 00b27fb..847f4d4 100644
--- a/src/pixie/masks.nim
+++ b/src/pixie/masks.nim
@@ -181,14 +181,14 @@ proc getValueSmooth*(mask: Mask, x, y: float32): uint8 {.raises: [].} =
 
   var topMix = x0y0
   if xFractional > 0 and x0y0 != x1y0:
-    topMix = lerp(x0y0, x1y0, xFractional)
+    topMix = mix(x0y0, x1y0, xFractional)
 
   var bottomMix = x0y1
   if xFractional > 0 and x0y1 != x1y1:
-    bottomMix = lerp(x0y1, x1y1, xFractional)
+    bottomMix = mix(x0y1, x1y1, xFractional)
 
   if yFractional != 0 and topMix != bottomMix:
-    lerp(topMix, bottomMix, yFractional)
+    mix(topMix, bottomMix, yFractional)
   else:
     topMix
 
diff --git a/src/pixie/paints.nim b/src/pixie/paints.nim
index 9baeda7..9b6ee64 100644
--- a/src/pixie/paints.nim
+++ b/src/pixie/paints.nim
@@ -95,7 +95,7 @@ proc gradientPut(
     let
       gs1 = stops[index]
       gs2 = stops[index + 1]
-    color = lerp(
+    color = mix(
       gs1.color,
       gs2.color,
       (t - gs1.position) / (gs2.position - gs1.position)
diff --git a/tests/benchmark_png.nim b/tests/benchmark_png.nim
index e2257d8..137977d 100644
--- a/tests/benchmark_png.nim
+++ b/tests/benchmark_png.nim
@@ -6,9 +6,16 @@ let
   data = readFile(filePath)
 
 timeIt "pixie decode":
-  keep decodePng(data)
+  keep decodePngRaw(data)
 
 timeIt "pixie encode":
+  let decoded = decodePngRaw(data)
+  keep encodePng(decoded).len
+
+timeIt "pixie decode + alpha":
+  keep decodePng(data)
+
+timeIt "pixie encode + alpha":
   let decoded = decodePng(data)
   keep encodePng(decoded).len