Reduce the color bit depth used within a JavaFX Image

ImagePaletteReducer.java

import javafx.application.Application;
import javafx.event.*;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.image.*;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

// displays a button with a 64 color image palette and a full color palette when pressed.
public class ImagePaletteReducer extends Application {
  @Override public void start(final Stage stage) throws Exception {
    final Label response = new Label("");
    final Image originalImage = new Image("http://icons.iconarchive.com/icons/eponas-deeway/colobrush/128/heart-2-icon.png");
    final Image resampledImage = resample(originalImage);
    final ImageView imageView = new ImageView(resampledImage);
    final Button button = new Button("I love you", imageView);
    button.setStyle("-fx-base: coral;");
    button.setContentDisplay(ContentDisplay.TOP);
    button.setOnAction(new EventHandler<ActionEvent>() {
      @Override public void handle(ActionEvent event) {
        if ("".equals(response.getText())) {
          response.setText("I love you too!");
          imageView.setImage(originalImage);
        } else {
          response.setText("");
          imageView.setImage(resampledImage);
        } 
      }
    });

    final VBox layout = new VBox(10);
    layout.setAlignment(Pos.CENTER);
    layout.getChildren().addAll(button, response);
    layout.setStyle("-fx-background-color: cornsilk; -fx-padding: 10; -fx-font-size: 20;");
    stage.setTitle("Heart");
    stage.getIcons().add(originalImage);
    stage.setScene(new Scene(layout));
    stage.show();
  }
  public static void main(String[] args) { launch(args); }

  // downsamples an image to a 64 color palette by only 
  // using the 2 most significant bits of color to represent
  // each of the image's pixels.
  private Image resample(Image inputImage) {
    int W = (int) inputImage.getWidth();
    int H = (int) inputImage.getHeight();
    WritableImage outputImage = new WritableImage(W, H);
    PixelReader reader = inputImage.getPixelReader();
    PixelWriter writer = outputImage.getPixelWriter();
    for (int y = 0; y < H; y++) {
      for (int x = 0; x < W; x++) {
        int argb = reader.getArgb(x, y);
        int a = (argb >> 24) & 0xFF;
        int r = (argb >> 16) & 0xFF;
        int g = (argb >>  8) & 0xFF;
        int b =  argb        & 0xFF;

        r = r & 0xC0;
        g = g & 0xC0;
        b = b & 0xC0;

        argb = (a << 24) | (r << 16) | (g << 8) | b;
        writer.setArgb(x, y, argb);
      }
    }

    return outputImage;
  }
}
// icon license: (creative commons with attribution) http://creativecommons.org/licenses/by-nc-nd/3.0/
// icon artist attribution page: (eponas-deeway) http://eponas-deeway.deviantart.com/gallery/#/d1s7uih

Answer to the StackOverflow question: Reduce number of colors and get color of a single pixel.

Uses the concept of ColorDepth.