diff --git a/README.md b/README.md
index cf92560..febfba4 100644
--- a/README.md
+++ b/README.md
@@ -21,7 +21,6 @@ Three.js powered Minecraft skin viewer.
 <script>
 	let skinViewer = new skinview3d.SkinViewer({
 		domElement: document.getElementById("skin_container"),
-		slim: true,
 		width: 600,
 		height: 600,
 		skinUrl: "img/skin.png",
diff --git a/examples/index.html b/examples/index.html
index f1043b0..14da4d3 100644
--- a/examples/index.html
+++ b/examples/index.html
@@ -16,12 +16,15 @@
 	<script>
 		let skinViewer = new skinview3d.SkinViewer({
 			domElement: document.getElementById("skin_container"),
-			slim: true,
 			width: 400,
 			height: 400,
 			skinUrl: "./1_8_texturemap_redux.png"
 		});
 
+		// By default, the skin model is automatically detected. You can turn it off in this way:
+		// skinViewer.detectModel = false;
+		// skinViewer.playerObject.skin.slim = true;
+
 		let control = new skinview3d.createOrbitControls(skinViewer);
 		skinViewer.animation = new skinview3d.CompositeAnimation();
 
diff --git a/src/skinview3d.js b/src/skinview3d.js
index f4069d9..5e4a698 100644
--- a/src/skinview3d.js
+++ b/src/skinview3d.js
@@ -1,6 +1,18 @@
-export { SkinObject, CapeObject, PlayerObject } from "./model";
-export { SkinViewer } from "./viewer";
-export { OrbitControls, createOrbitControls } from "./orbit_controls";
+export {
+	SkinObject,
+	CapeObject,
+	PlayerObject
+} from "./model";
+
+export {
+	SkinViewer
+} from "./viewer";
+
+export {
+	OrbitControls,
+	createOrbitControls
+} from "./orbit_controls";
+
 export {
 	invokeAnimation,
 	CompositeAnimation,
@@ -8,3 +20,7 @@ export {
 	RunningAnimation,
 	RotatingAnimation
 } from "./animation";
+
+export {
+	isSlimSkin
+} from "./utils";
diff --git a/src/utils.js b/src/utils.js
new file mode 100644
index 0000000..b24dc81
--- /dev/null
+++ b/src/utils.js
@@ -0,0 +1,179 @@
+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(context, width) {
+	let scale = computeSkinScale(width);
+	let copySkin = (sX, sY, w, h, dX, dY, flipHorizontal) => copyImage(context, 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 loadSkinToCanvas(canvas, image) {
+	let isOldFormat = false;
+	if (image.width !== image.height) {
+		if (image.width === 2 * image.height) {
+			isOldFormat = true;
+		} else {
+			throw `Bad skin size: ${image.width}x${image.height}`;
+		}
+	}
+
+	let context = canvas.getContext("2d");
+	if (isOldFormat) {
+		let sideLength = image.width;
+		canvas.width = sideLength;
+		canvas.height = sideLength;
+		context.clearRect(0, 0, sideLength, sideLength);
+		context.drawImage(image, 0, 0, sideLength, sideLength / 2.0);
+		convertSkinTo1_8(context, sideLength);
+	} else {
+		canvas.width = image.width;
+		canvas.height = image.height;
+		context.clearRect(0, 0, image.width, image.height);
+		context.drawImage(image, 0, 0, canvas.width, canvas.height);
+	}
+}
+
+function loadCapeToCanvas(canvas, image) {
+	let isOldFormat = false;
+	if (image.width !== 2 * image.height) {
+		if (image.width * 17 == image.height * 22) {
+			// width/height = 22/17
+			isOldFormat = true;
+		} else {
+			throw `Bad cape size: ${image.width}x${image.height}`;
+		}
+	}
+
+	let context = canvas.getContext("2d");
+	if (isOldFormat) {
+		let width = image.width * 64 / 22;
+		canvas.width = width;
+		canvas.height = width / 2;
+	} else {
+		canvas.width = image.width;
+		canvas.height = image.height;
+	}
+	context.clearRect(0, 0, canvas.width, canvas.height);
+	context.drawImage(image, 0, 0, image.width, image.height);
+}
+
+function isSlimSkin(canvasOrImage) {
+	// 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.
+
+	if (canvasOrImage instanceof HTMLCanvasElement) {
+		let canvas = canvasOrImage;
+		let scale = computeSkinScale(canvas.width);
+		let context = canvas.getContext("2d");
+		let checkArea = (x, y, w, h) => hasTransparency(context, 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);
+	} else if (canvasOrImage instanceof HTMLImageElement) {
+		let image = canvasOrImage;
+		let canvas = document.createElement("canvas");
+		loadSkinToCanvas(canvas, image);
+		return isSlimSkin(canvas);
+	} else {
+		throw `Illegal argument: ${canvasOrImage}`;
+	}
+}
+
+export { isSlimSkin, loadSkinToCanvas, loadCapeToCanvas };
diff --git a/src/viewer.js b/src/viewer.js
index fd30c8c..6676933 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -1,61 +1,13 @@
 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 convertSkinTo1_8(context, width) {
-	let scale = width / 64.0;
-	let copySkin = (context, sX, sY, w, h, dX, dY, flipHorizontal) => copyImage(context, sX * scale, sY * scale, w * scale, h * scale, dX * scale, dY * scale, flipHorizontal);
-
-	copySkin(context, 4, 16, 4, 4, 20, 48, true); // Top Leg
-	copySkin(context, 8, 16, 4, 4, 24, 48, true); // Bottom Leg
-	copySkin(context, 0, 20, 4, 12, 24, 52, true); // Outer Leg
-	copySkin(context, 4, 20, 4, 12, 20, 52, true); // Front Leg
-	copySkin(context, 8, 20, 4, 12, 16, 52, true); // Inner Leg
-	copySkin(context, 12, 20, 4, 12, 28, 52, true); // Back Leg
-	copySkin(context, 44, 16, 4, 4, 36, 48, true); // Top Arm
-	copySkin(context, 48, 16, 4, 4, 40, 48, true); // Bottom Arm
-	copySkin(context, 40, 20, 4, 12, 40, 52, true); // Outer Arm
-	copySkin(context, 44, 20, 4, 12, 36, 52, true); // Front Arm
-	copySkin(context, 48, 20, 4, 12, 32, 52, true); // Inner Arm
-	copySkin(context, 52, 20, 4, 12, 44, 52, true); // Back Arm
-}
+import { loadSkinToCanvas,loadCapeToCanvas, isSlimSkin } from "./utils";
 
 class SkinViewer {
 	constructor(options) {
 		this.domElement = options.domElement;
 		this.animation = options.animation || null;
+		this.detectModel = options.animation !== false; // true by default
 		this.animationPaused = false;
 		this.animationTime = 0;
 		this.disposed = false;
@@ -91,36 +43,16 @@ class SkinViewer {
 		this.domElement.appendChild(this.renderer.domElement);
 
 		this.playerObject = new PlayerObject(this.layer1Material, this.layer2Material, this.capeMaterial);
-		this.playerObject.skin.slim = options.slim === true;
 		this.scene.add(this.playerObject);
 
 		// texture loading
 		this.skinImg.crossOrigin = "anonymous";
 		this.skinImg.onerror = () => console.error("Failed loading " + this.skinImg.src);
 		this.skinImg.onload = () => {
-			let isOldFormat = false;
-			if (this.skinImg.width !== this.skinImg.height) {
-				if (this.skinImg.width === 2 * this.skinImg.height) {
-					isOldFormat = true;
-				} else {
-					console.error("Bad skin size");
-					return;
-				}
-			}
+			loadSkinToCanvas(this.skinCanvas, this.skinImg);
 
-			let skinContext = this.skinCanvas.getContext("2d");
-			if (isOldFormat) {
-				let width = this.skinImg.width;
-				this.skinCanvas.width = width;
-				this.skinCanvas.height = width;
-				skinContext.clearRect(0, 0, width, width);
-				skinContext.drawImage(this.skinImg, 0, 0, width, width / 2.0);
-				convertSkinTo1_8(skinContext, width);
-			} else {
-				this.skinCanvas.width = this.skinImg.width;
-				this.skinCanvas.height = this.skinImg.height;
-				skinContext.clearRect(0, 0, this.skinCanvas.width, this.skinCanvas.height);
-				skinContext.drawImage(this.skinImg, 0, 0, this.skinCanvas.width, this.skinCanvas.height);
+			if (this.detectModel) {
+				this.playerObject.skin.slim = isSlimSkin(this.skinCanvas);
 			}
 
 			this.skinTexture.needsUpdate = true;
@@ -133,28 +65,7 @@ class SkinViewer {
 		this.capeImg.crossOrigin = "anonymous";
 		this.capeImg.onerror = () => console.error("Failed loading " + this.capeImg.src);
 		this.capeImg.onload = () => {
-			let isOldFormat = false;
-			if (this.capeImg.width !== 2 * this.capeImg.height) {
-				if (this.capeImg.width * 17 == this.capeImg.height * 22) {
-					// width/height = 22/17
-					isOldFormat = true;
-				} else {
-					console.error("Bad cape size");
-					return;
-				}
-			}
-
-			let capeContext = this.capeCanvas.getContext("2d");
-			if (isOldFormat) {
-				let width = this.capeImg.width * 64 / 22;
-				this.capeCanvas.width = width;
-				this.capeCanvas.height = width / 2;
-			} else {
-				this.capeCanvas.width = this.capeImg.width;
-				this.capeCanvas.height = this.capeImg.height;
-			}
-			capeContext.clearRect(0, 0, this.capeCanvas.width, this.capeCanvas.height);
-			capeContext.drawImage(this.capeImg, 0, 0, this.capeImg.width, this.capeImg.height);
+			loadCapeToCanvas(this.capeCanvas, this.capeImg);
 
 			this.capeTexture.needsUpdate = true;
 			this.capeMaterial.needsUpdate = true;
diff --git a/types/skinview3d.d.ts b/types/skinview3d.d.ts
index befec93..8d093fc 100644
--- a/types/skinview3d.d.ts
+++ b/types/skinview3d.d.ts
@@ -2,3 +2,4 @@ export * from "./model";
 export * from "./animation";
 export * from "./viewer";
 export * from "./orbit_controls";
+export * from "./utils";
diff --git a/types/utils.d.ts b/types/utils.d.ts
new file mode 100644
index 0000000..26be80c
--- /dev/null
+++ b/types/utils.d.ts
@@ -0,0 +1 @@
+export function isSlimSkin(skinImage: HTMLImageElement): boolean;
diff --git a/types/viewer.d.ts b/types/viewer.d.ts
index 6259cbb..a5182c9 100644
--- a/types/viewer.d.ts
+++ b/types/viewer.d.ts
@@ -5,11 +5,11 @@ import { PlayerObject } from "./model";
 export interface SkinViewerOptions {
 	domElement: Node;
 	animation?: Animation;
-	slim?: boolean;
 	skinUrl?: string;
 	capeUrl?: string;
 	width?: number;
 	height?: number;
+	detectModel?: boolean;
 }
 
 export class SkinViewer {
@@ -22,6 +22,7 @@ export class SkinViewer {
 	public animation: Animation;
 	public animationPaused: boolean;
 	public animationTime: number;
+	public detectModel: boolean;
 	public readonly playerObject: PlayerObject;
 	public readonly scene: THREE.Scene;
 	public readonly camera: THREE.PerspectiveCamera;