diff --git a/Sources/geometrize/Bitmap.swift b/Sources/geometrize/Bitmap.swift
index 8f39eb6..3de0877 100644
--- a/Sources/geometrize/Bitmap.swift
+++ b/Sources/geometrize/Bitmap.swift
@@ -52,7 +52,7 @@ public struct Bitmap {
                 for y in 0..<height {
                     for x in 0..<width {
                         let offset = (width * y + x) * 4
-                        let rgba = Rgba(r: data[offset + 0], g: data[offset + 1], b: data[offset + 2], a: data[offset + 3]).blending(background: background)
+                        let rgba = Rgba(data[offset..<offset+4]).blending(background: background)
                         buffer[offset + 0] = rgba.r
                         buffer[offset + 1] = rgba.g
                         buffer[offset + 2] = rgba.b
@@ -132,7 +132,7 @@ public struct Bitmap {
         get {
             backing.withUnsafeBufferPointer {
                 let offset = offset(x: x, y: y)
-                return Rgba(r: $0[offset], g: $0[offset + 1], b: $0[offset + 2], a: $0[offset + 3])
+                return Rgba($0[offset..<offset + 4])
             }
         }
         set {
diff --git a/Sources/geometrize/Rgba.swift b/Sources/geometrize/Rgba.swift
index c26b024..0f556c1 100644
--- a/Sources/geometrize/Rgba.swift
+++ b/Sources/geometrize/Rgba.swift
@@ -15,6 +15,38 @@ public struct Rgba {
         self.a = a
     }
 
+    public init(_ array: [UInt8]) {
+        assert(array.count == 4)
+        self.r = array[0]
+        self.g = array[1]
+        self.b = array[2]
+        self.a = array[3]
+    }
+
+    public init(_ slice: ArraySlice<UInt8>) {
+        assert(slice.count == 4)
+        self.r = slice[slice.startIndex]
+        self.g = slice[slice.startIndex + 1]
+        self.b = slice[slice.startIndex + 2]
+        self.a = slice[slice.startIndex + 3]
+    }
+
+    public init(_ buffer: UnsafeBufferPointer<UInt8>) {
+        assert(buffer.count == 4)
+        self.r = buffer[0]
+        self.g = buffer[1]
+        self.b = buffer[2]
+        self.a = buffer[3]
+    }
+
+    public init(_ slice: Slice<UnsafeBufferPointer<UInt8>>) {
+        assert(slice.count == 4)
+        self.r = slice[slice.startIndex]
+        self.g = slice[slice.startIndex + 1]
+        self.b = slice[slice.startIndex + 2]
+        self.a = slice[slice.startIndex + 3]
+    }
+
     public func withAlphaComponent(_ alpha: UInt8) -> Rgba {
         Rgba(r: r, g: g, b: b, a: alpha)
     }