diff --git a/src/codecs/encoders.ts b/src/codecs/encoders.ts
index 074d06cd..6c901fb0 100644
--- a/src/codecs/encoders.ts
+++ b/src/codecs/encoders.ts
@@ -10,6 +10,8 @@ import * as browserJP2 from './browser-jp2/encoder';
 import * as browserBMP from './browser-bmp/encoder';
 import * as browserPDF from './browser-pdf/encoder';
 
+import * as quantizer from './imagequant/quantizer';
+
 export interface EncoderSupportMap {
   [key: string]: boolean;
 }
@@ -26,6 +28,13 @@ export type EncoderOptions =
   browserPDF.EncodeOptions;
 export type EncoderType = keyof typeof encoderMap;
 
+export interface Enableable {
+  enabled: boolean;
+}
+export interface PreprocessorState {
+  quantizer: Enableable & quantizer.QuantizeOptions;
+}
+
 export const encoderMap = {
   [identity.type]: identity,
   [mozJPEG.type]: mozJPEG,
diff --git a/src/codecs/imagequant/options.tsx b/src/codecs/imagequant/options.tsx
index 6b22c8f0..5ea1c0fd 100644
--- a/src/codecs/imagequant/options.tsx
+++ b/src/codecs/imagequant/options.tsx
@@ -31,7 +31,7 @@ export default class QuantizerOptions extends Component<Props, {}> {
     return (
       <form>
         <label>
-          Pallette Color:
+          Pallette Colors:
           <input
             name="maxNumColors"
             type="range"
diff --git a/src/codecs/imagequant/quantizer.ts b/src/codecs/imagequant/quantizer.ts
index 7a14cac7..cb0bb2fc 100644
--- a/src/codecs/imagequant/quantizer.ts
+++ b/src/codecs/imagequant/quantizer.ts
@@ -11,7 +11,6 @@ export interface QuantizeOptions {
   dither: number;
 }
 
-// These come from struct WebPConfig in encode.h.
 export const defaultOptions: QuantizeOptions = {
   maxNumColors: 256,
   dither: 1.0,
diff --git a/src/components/App/index.tsx b/src/components/App/index.tsx
index 9a6215b5..fd153e6c 100644
--- a/src/components/App/index.tsx
+++ b/src/components/App/index.tsx
@@ -25,6 +25,7 @@ import {
     EncoderType,
     EncoderOptions,
     encoderMap,
+    PreprocessorState,
 } from '../../codecs/encoders';
 
 import { decodeImage } from '../../codecs/decoders';
@@ -33,12 +34,14 @@ interface SourceImage {
   file: File;
   bmp: ImageBitmap;
   data: ImageData;
+  preprocessed?: ImageData;
 }
 
 interface EncodedImage {
   bmp?: ImageBitmap;
   file?: File;
   downloadUrl?: string;
+  preprocessorState: PreprocessorState;
   encoderState: EncoderState;
   loading: boolean;
   /** Counter of the latest bmp currently encoding */
@@ -58,17 +61,26 @@ interface State {
 
 const filesize = partial({});
 
+async function preprocessImage(
+  source: SourceImage,
+  preprocessData: PreprocessorState,
+): Promise<ImageData> {
+  let result = source.data;
+  if (preprocessData.quantizer.enabled) {
+    result = await quantizer.quantize(result, preprocessData.quantizer);
+  }
+  return result;
+}
 async function compressImage(
   source: SourceImage,
-  quantizerOptions: quantizer.QuantizeOptions | null,
   encodeData: EncoderState,
 ): Promise<File> {
   // Special case for identity
   if (encodeData.type === identity.type) return source.file;
 
   let sourceData = source.data;
-  if (quantizerOptions) {
-    sourceData = await quantizer.quantize(sourceData, quantizerOptions);
+  if (source.preprocessed) {
+    sourceData = source.preprocessed;
   }
   const compressedData = await (() => {
     switch (encodeData.type) {
@@ -100,12 +112,24 @@ export default class App extends Component<Props, State> {
     loading: false,
     images: [
       {
+        preprocessorState: {
+          quantizer: {
+            enabled: false,
+            ...quantizer.defaultOptions,
+          },
+        },
         encoderState: { type: identity.type, options: identity.defaultOptions },
         loadingCounter: 0,
         loadedCounter: 0,
         loading: false,
       },
       {
+        preprocessorState: {
+          quantizer: {
+            enabled: false,
+            ...quantizer.defaultOptions,
+          },
+        },
         encoderState: { type: mozJPEG.type, options: mozJPEG.defaultOptions },
         loadingCounter: 0,
         loadedCounter: 0,
@@ -127,7 +151,12 @@ export default class App extends Component<Props, State> {
     }
   }
 
-  onEncoderChange(index: 0 | 1, type: EncoderType, options?: EncoderOptions): void {
+  onChange(
+    index: 0 | 1,
+    preprocessorState: PreprocessorState,
+    type: EncoderType,
+    options?: EncoderOptions,
+  ): void {
     const images = this.state.images.slice() as [EncodedImage, EncodedImage];
     const oldImage = images[index];
 
@@ -142,13 +171,32 @@ export default class App extends Component<Props, State> {
     images[index] = {
       ...oldImage,
       encoderState,
+      preprocessorState,
     };
 
     this.setState({ images });
   }
 
-  onOptionsChange(index: 0 | 1, options: EncoderOptions): void {
-    this.onEncoderChange(index, this.state.images[index].encoderState.type, options);
+  onEncoderTypeChange(index: 0 | 1, newType: EncoderType): void {
+    this.onChange(index, this.state.images[index].preprocessorState, newType);
+  }
+
+  onPreprocessorOptionsChange(index: 0 | 1, options: PreprocessorState): void {
+    this.onChange(
+      index,
+      options,
+      this.state.images[index].encoderState.type,
+      this.state.images[index].encoderState.options,
+    );
+  }
+
+  onEncoderOptionsChange(index: 0 | 1, options: EncoderOptions): void {
+    this.onChange(
+      index,
+      this.state.images[index].preprocessorState,
+      this.state.images[index].encoderState.type,
+      options,
+    );
   }
 
   componentDidUpdate(prevProps: Props, prevState: State): void {
@@ -218,10 +266,9 @@ export default class App extends Component<Props, State> {
     this.setState({ images });
 
     let file;
-
     try {
-      // FIXME (@surma): Somehow show a options window and get the values from there.
-      file = await compressImage(source, { maxNumColors: 8, dither: 0.5 }, image.encoderState);
+      source.preprocessed = await preprocessImage(source, image.preprocessorState);
+      file = await compressImage(source, image.encoderState);
     } catch (err) {
       this.setState({ error: `Encoding error (type=${image.encoderState.type}): ${err}` });
       throw err;
@@ -283,9 +330,11 @@ export default class App extends Component<Props, State> {
           {images.map((image, index) => (
             <Options
               class={index ? style.rightOptions : style.leftOptions}
+              preprocessorState={image.preprocessorState}
               encoderState={image.encoderState}
-              onTypeChange={this.onEncoderChange.bind(this, index)}
-              onOptionsChange={this.onOptionsChange.bind(this, index)}
+              onEncoderTypeChange={this.onEncoderTypeChange.bind(this, index)}
+              onEncoderOptionsChange={this.onEncoderOptionsChange.bind(this, index)}
+              onPreprocessorOptionsChange={this.onPreprocessorOptionsChange.bind(this, index)}
             />
           ))}
           {anyLoading && <span style={{ position: 'fixed', top: 0, left: 0 }}>Loading...</span>}
diff --git a/src/components/Options/index.tsx b/src/components/Options/index.tsx
index 377707c7..7ddf5427 100644
--- a/src/components/Options/index.tsx
+++ b/src/components/Options/index.tsx
@@ -6,6 +6,8 @@ import BrowserJPEGEncoderOptions from '../../codecs/browser-jpeg/options';
 import WebPEncoderOptions from '../../codecs/webp/options';
 import BrowserWebPEncoderOptions from '../../codecs/browser-webp/options';
 
+import QuantizerOptions from '../../codecs/imagequant/options';
+
 import * as identity from '../../codecs/identity/encoder';
 import * as mozJPEG from '../../codecs/mozjpeg/encoder';
 import * as webP from '../../codecs/webp/encoder';
@@ -24,6 +26,7 @@ import {
     encoders,
     encodersSupported,
     EncoderSupportMap,
+    PreprocessorState,
 } from '../../codecs/encoders';
 
 const encoderOptionsComponentMap = {
@@ -44,8 +47,10 @@ const encoderOptionsComponentMap = {
 interface Props {
   class?: string;
   encoderState: EncoderState;
-  onTypeChange(newType: EncoderType): void;
-  onOptionsChange(newOptions: EncoderOptions): void;
+  preprocessorState: PreprocessorState;
+  onEncoderTypeChange(newType: EncoderType): void;
+  onEncoderOptionsChange(newOptions: EncoderOptions): void;
+  onPreprocessorOptionsChange(newOptions: PreprocessorState): void;
 }
 
 interface State {
@@ -61,25 +66,64 @@ export default class Options extends Component<Props, State> {
   }
 
   @bind
-  onTypeChange(event: Event) {
+  onEncoderTypeChange(event: Event) {
     const el = event.currentTarget as HTMLSelectElement;
 
     // The select element only has values matching encoder types,
     // so 'as' is safe here.
     const type = el.value as EncoderType;
-    this.props.onTypeChange(type);
+    this.props.onEncoderTypeChange(type);
   }
 
-  render({ class: className, encoderState, onOptionsChange }: Props, { encoderSupportMap }: State) {
+  @bind
+  onPreprocessorEnabledChange(event: Event) {
+    const el = event.currentTarget as HTMLInputElement;
+
+    const preprocessorState = this.props.preprocessorState;
+    const preprocessor = el.name.split('.')[0] as keyof typeof preprocessorState;
+    preprocessorState[preprocessor].enabled = el.checked;
+    this.props.onPreprocessorOptionsChange(preprocessorState);
+  }
+
+  render(
+    { class: className, encoderState, preprocessorState, onEncoderOptionsChange }: Props,
+    { encoderSupportMap }: State,
+  ) {
     // tslint:disable variable-name
     const EncoderOptionComponent = encoderOptionsComponentMap[encoderState.type];
 
     return (
       <div class={`${style.options}${className ? (' ' + className) : ''}`}>
+        <p>Quantization</p>
+        <label>
+          <input
+            name="quantizer.enable"
+            type="checkbox"
+            checked={!!preprocessorState.quantizer.enabled}
+            onChange={this.onPreprocessorEnabledChange}
+          />
+          Enable
+        </label>
+        {preprocessorState.quantizer.enabled ? (
+          <QuantizerOptions
+            options={preprocessorState.quantizer}
+            // tslint:disable-next-line:jsx-no-lambda
+            onChange={quantizeOpts => this.props.onPreprocessorOptionsChange({
+              ...preprocessorState,
+              quantizer: {
+                ...quantizeOpts,
+                enabled: preprocessorState.quantizer.enabled,
+              },
+            })}
+          />
+        ) : (
+          <div/>
+        )}
+        <hr/>
         <label>
           Mode:
           {encoderSupportMap ?
-            <select value={encoderState.type} onChange={this.onTypeChange}>
+            <select value={encoderState.type} onChange={this.onEncoderTypeChange}>
               {encoders.filter(encoder => encoderSupportMap[encoder.type]).map(encoder => (
                 <option value={encoder.type}>{encoder.label}</option>
               ))}
@@ -95,7 +139,7 @@ export default class Options extends Component<Props, State> {
               // type, but typescript isn't smart enough.
               encoderState.options as typeof EncoderOptionComponent['prototype']['props']['options']
             }
-            onChange={onOptionsChange}
+            onChange={onEncoderOptionsChange}
           />
         }
       </div>