diff --git a/src/utils.js b/src/utils.js
new file mode 100644
index 0000000..206ea8c
--- /dev/null
+++ b/src/utils.js
@@ -0,0 +1,118 @@
+function copyImage(context, sX, sY, w, h, dX, dY, flipHorizontal) {
+	let imgData = context.getImageData(sX, sY, w, h);
+	if (flipHorizontal) {
+		for (let y = 0; y < h; y++) {
+			for (let x = 0; x < (w / 2); x++) {
+				let index = (x + y * w) * 4;
+				let index2 = ((w - x - 1) + y * w) * 4;
+				let pA1 = imgData.data[index];
+				let pA2 = imgData.data[index + 1];
+				let pA3 = imgData.data[index + 2];
+				let pA4 = imgData.data[index + 3];
+
+				let pB1 = imgData.data[index2];
+				let pB2 = imgData.data[index2 + 1];
+				let pB3 = imgData.data[index2 + 2];
+				let pB4 = imgData.data[index2 + 3];
+
+				imgData.data[index] = pB1;
+				imgData.data[index + 1] = pB2;
+				imgData.data[index + 2] = pB3;
+				imgData.data[index + 3] = pB4;
+
+				imgData.data[index2] = pA1;
+				imgData.data[index2 + 1] = pA2;
+				imgData.data[index2 + 2] = pA3;
+				imgData.data[index2 + 3] = pA4;
+			}
+		}
+	}
+	context.putImageData(imgData, dX, dY);
+}
+
+function hasTransparency(context, x0, y0, w, h) {
+	let imgData = context.getImageData(x0, y0, w, h);
+	for (let x = 0; x < w; x++) {
+		for (let y = 0; y < h; y++) {
+			let offset = (x + y * w) * 4;
+			if (imgData.data[offset + 3] !== 0xff) {
+				return true;
+			}
+		}
+	}
+	return false;
+}
+
+function computeSkinScale(width) {
+	return width / 64.0;
+}
+
+function convertSkinTo1_8(skinContext, width) {
+	let scale = computeSkinScale(width);
+	let copySkin = (sX, sY, w, h, dX, dY, flipHorizontal) => copyImage(skinContext, sX * scale, sY * scale, w * scale, h * scale, dX * scale, dY * scale, flipHorizontal);
+
+	copySkin(4, 16, 4, 4, 20, 48, true); // Top Leg
+	copySkin(8, 16, 4, 4, 24, 48, true); // Bottom Leg
+	copySkin(0, 20, 4, 12, 24, 52, true); // Outer Leg
+	copySkin(4, 20, 4, 12, 20, 52, true); // Front Leg
+	copySkin(8, 20, 4, 12, 16, 52, true); // Inner Leg
+	copySkin(12, 20, 4, 12, 28, 52, true); // Back Leg
+	copySkin(44, 16, 4, 4, 36, 48, true); // Top Arm
+	copySkin(48, 16, 4, 4, 40, 48, true); // Bottom Arm
+	copySkin(40, 20, 4, 12, 40, 52, true); // Outer Arm
+	copySkin(44, 20, 4, 12, 36, 52, true); // Front Arm
+	copySkin(48, 20, 4, 12, 32, 52, true); // Inner Arm
+	copySkin(52, 20, 4, 12, 44, 52, true); // Back Arm
+}
+
+function isSlimSkin(skinContext, width) {
+	// Detects whether the skin is default or slim.
+	//
+	// The right arm area of *default* skins:
+	// (44,16)->*-------*-------*
+	// (40,20)  |top    |bottom |
+	// \|/      |4x4    |4x4    |
+	//  *-------*-------*-------*-------*
+	//  |right  |front  |left   |back   |
+	//  |4x12   |4x12   |4x12   |4x12   |
+	//  *-------*-------*-------*-------*
+	// The right arm area of *slim* skins:
+	// (44,16)->*------*------*-*
+	// (40,20)  |top   |bottom| |<----[x0=50,y0=16,w=2,h=4]
+	// \|/      |3x4   |3x4   | |
+	//  *-------*------*------***-----*-*
+	//  |right  |front |left   |back  | |<----[x0=54,y0=20,w=2,h=12]
+	//  |4x12   |3x12  |4x12   |3x12  | |
+	//  *-------*------*-------*------*-*
+	// Compared with default right arms, slim right arms have 2 unused areas.
+	//
+	// The same is true for left arm:
+	// The left arm area of *default* skins:
+	// (36,48)->*-------*-------*
+	// (32,52)  |top    |bottom |
+	// \|/      |4x4    |4x4    |
+	//  *-------*-------*-------*-------*
+	//  |right  |front  |left   |back   |
+	//  |4x12   |4x12   |4x12   |4x12   |
+	//  *-------*-------*-------*-------*
+	// The left arm area of *slim* skins:
+	// (36,48)->*------*------*-*
+	// (32,52)  |top   |bottom| |<----[x0=42,y0=48,w=2,h=4]
+	// \|/      |3x4   |3x4   | |
+	//  *-------*------*------***-----*-*
+	//  |right  |front |left   |back  | |<----[x0=46,y0=52,w=2,h=12]
+	//  |4x12   |3x12  |4x12   |3x12  | |
+	//  *-------*------*-------*------*-*
+	//
+	// If there is a transparent pixel in any of the 4 unused areas, the skin must be slim,
+	// as transparent pixels are not allowed in the first layer.
+
+	let scale = computeSkinScale(width);
+	let checkArea = (x, y, w, h) => hasTransparency(skinContext, x * scale, y * scale, w * scale, h * scale);
+	return checkArea(50, 16, 2, 4) ||
+		checkArea(54, 20, 2, 12) ||
+		checkArea(42, 48, 2, 4) ||
+		checkArea(46, 52, 2, 12);
+}
+
+export { convertSkinTo1_8, isSlimSkin };
diff --git a/src/viewer.js b/src/viewer.js
index dbab733..b9062f5 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -1,123 +1,7 @@
 import * as THREE from "three";
 import { PlayerObject } from "./model";
 import { invokeAnimation } from "./animation";
-
-function copyImage(context, sX, sY, w, h, dX, dY, flipHorizontal) {
-	let imgData = context.getImageData(sX, sY, w, h);
-	if (flipHorizontal) {
-		for (let y = 0; y < h; y++) {
-			for (let x = 0; x < (w / 2); x++) {
-				let index = (x + y * w) * 4;
-				let index2 = ((w - x - 1) + y * w) * 4;
-				let pA1 = imgData.data[index];
-				let pA2 = imgData.data[index + 1];
-				let pA3 = imgData.data[index + 2];
-				let pA4 = imgData.data[index + 3];
-
-				let pB1 = imgData.data[index2];
-				let pB2 = imgData.data[index2 + 1];
-				let pB3 = imgData.data[index2 + 2];
-				let pB4 = imgData.data[index2 + 3];
-
-				imgData.data[index] = pB1;
-				imgData.data[index + 1] = pB2;
-				imgData.data[index + 2] = pB3;
-				imgData.data[index + 3] = pB4;
-
-				imgData.data[index2] = pA1;
-				imgData.data[index2 + 1] = pA2;
-				imgData.data[index2 + 2] = pA3;
-				imgData.data[index2 + 3] = pA4;
-			}
-		}
-	}
-	context.putImageData(imgData, dX, dY);
-}
-
-function hasTransparency(context, x0, y0, w, h) {
-	let imgData = context.getImageData(x0, y0, w, h);
-	for (let x = 0; x < w; x++) {
-		for (let y = 0; y < h; y++) {
-			let offset = (x + y * w) * 4;
-			if (imgData.data[offset + 3] !== 0xff) {
-				return true;
-			}
-		}
-	}
-	return false;
-}
-
-function computeSkinScale(width) {
-	return width / 64.0;
-}
-
-function convertSkinTo1_8(skinContext, width) {
-	let scale = computeSkinScale(width);
-	let copySkin = (sX, sY, w, h, dX, dY, flipHorizontal) => copyImage(skinContext, sX * scale, sY * scale, w * scale, h * scale, dX * scale, dY * scale, flipHorizontal);
-
-	copySkin(4, 16, 4, 4, 20, 48, true); // Top Leg
-	copySkin(8, 16, 4, 4, 24, 48, true); // Bottom Leg
-	copySkin(0, 20, 4, 12, 24, 52, true); // Outer Leg
-	copySkin(4, 20, 4, 12, 20, 52, true); // Front Leg
-	copySkin(8, 20, 4, 12, 16, 52, true); // Inner Leg
-	copySkin(12, 20, 4, 12, 28, 52, true); // Back Leg
-	copySkin(44, 16, 4, 4, 36, 48, true); // Top Arm
-	copySkin(48, 16, 4, 4, 40, 48, true); // Bottom Arm
-	copySkin(40, 20, 4, 12, 40, 52, true); // Outer Arm
-	copySkin(44, 20, 4, 12, 36, 52, true); // Front Arm
-	copySkin(48, 20, 4, 12, 32, 52, true); // Inner Arm
-	copySkin(52, 20, 4, 12, 44, 52, true); // Back Arm
-}
-
-function isSlimSkin(skinContext, width) {
-	// Detects whether the skin is default or slim.
-	//
-	// The right arm area of *default* skins:
-	// (44,16)->*-------*-------*
-	// (40,20)  |top    |bottom |
-	// \|/      |4x4    |4x4    |
-	//  *-------*-------*-------*-------*
-	//  |right  |front  |left   |back   |
-	//  |4x12   |4x12   |4x12   |4x12   |
-	//  *-------*-------*-------*-------*
-	// The right arm area of *slim* skins:
-	// (44,16)->*------*------*-*
-	// (40,20)  |top   |bottom| |<----[x0=50,y0=16,w=2,h=4]
-	// \|/      |3x4   |3x4   | |
-	//  *-------*------*------***-----*-*
-	//  |right  |front |left   |back  | |<----[x0=54,y0=20,w=2,h=12]
-	//  |4x12   |3x12  |4x12   |3x12  | |
-	//  *-------*------*-------*------*-*
-	// Compared with default right arms, slim right arms have 2 unused areas.
-	//
-	// The same is true for left arm:
-	// The left arm area of *default* skins:
-	// (36,48)->*-------*-------*
-	// (32,52)  |top    |bottom |
-	// \|/      |4x4    |4x4    |
-	//  *-------*-------*-------*-------*
-	//  |right  |front  |left   |back   |
-	//  |4x12   |4x12   |4x12   |4x12   |
-	//  *-------*-------*-------*-------*
-	// The left arm area of *slim* skins:
-	// (36,48)->*------*------*-*
-	// (32,52)  |top   |bottom| |<----[x0=42,y0=48,w=2,h=4]
-	// \|/      |3x4   |3x4   | |
-	//  *-------*------*------***-----*-*
-	//  |right  |front |left   |back  | |<----[x0=46,y0=52,w=2,h=12]
-	//  |4x12   |3x12  |4x12   |3x12  | |
-	//  *-------*------*-------*------*-*
-	//
-	// If there is a transparent pixel in any of the 4 unused areas, the skin must be slim,
-	// as transparent pixels are not allowed in the first layer.
-
-	let scale = computeSkinScale(width);
-	let checkArea = (x, y, w, h) => hasTransparency(skinContext, x * scale, y * scale, w * scale, h * scale);
-	return checkArea(50, 16, 2, 4) ||
-		checkArea(54, 20, 2, 12) ||
-		checkArea(42, 48, 2, 4) ||
-		checkArea(46, 52, 2, 12);
-}
+import { convertSkinTo1_8, isSlimSkin} from "./utils";
 
 class SkinViewer {
 	constructor(options) {