Demonstrates different methods of scaling images in JavaFX and the effects of scaling with each.

ImageScaler.java

import javafx.application.*;
import javafx.geometry.HPos;
import javafx.geometry.Pos;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.image.*;
import javafx.scene.layout.*;
import javafx.stage.Stage;
 
public class ImageScaler extends Application {
  private static final String IMAGE_LOC = 
    "http://icons.iconarchive.com/icons/martin-berube/character/32/Robot-icon.png";
  
  private static final int SCALE_FACTOR = 6;
  
  private Image image;
  private int   scaledImageSize;
  
  @Override public void init() {
    image = new Image(
      IMAGE_LOC
    );
    
    scaledImageSize = (int) image.getWidth() * SCALE_FACTOR;
  }
  
  @Override public void start(Stage stage) {
    GridPane layout = new GridPane();
    layout.setHgap(10);
    layout.setVgap(10);
    
    ImageView originalImageView = new ImageView(image);
    StackPane originalImageViewStack = new StackPane();
    originalImageViewStack.getChildren().add(originalImageView);
    originalImageViewStack.setMinWidth(scaledImageSize);
    
    ImageView fittedImageView = new ImageView(image);
    fittedImageView.setSmooth(false);
    fittedImageView.setFitWidth(scaledImageSize);
    fittedImageView.setFitHeight(scaledImageSize);
    
    ImageView scaledImageView = new ImageView(image);
    scaledImageView.setSmooth(false);
    scaledImageView.setScaleX(SCALE_FACTOR);
    scaledImageView.setScaleY(SCALE_FACTOR);
    Group scaledImageViewGroup = new Group(scaledImageView);
    
    ImageView sizedImageInView = new ImageView(
      new Image(
        IMAGE_LOC, 
        scaledImageSize, 
        scaledImageSize, 
        false, 
        false
      )
    );

    ImageView resampledImageView = new ImageView(
      resample(
        image, 
        SCALE_FACTOR
      )
    );
    
    layout.addRow(
      0, 
        withTooltip(
          originalImageViewStack,
          "Unmodified image"
        ),
        withTooltip(
          sizedImageInView,
          "Image sized in Image constructor - Image smoothing false"
        ),
        withTooltip(
          fittedImageView,
          "Image fitted using ImageView fitWidth/fitHeight - ImageView smoothing false"
        ),
        withTooltip(
          scaledImageViewGroup,
          "ImageView scaled with Node scaleX/scaleY - ImageView smoothing false"
        ),
        withTooltip(
          resampledImageView,
          "Image manually recreated as a new WritableImage using a PixelWriter"
        )
    );
    
    layout.addRow(
      1, 
        centeredLabel("Original"),
        centeredLabel("Sized"),
        centeredLabel("Fitted"),
        centeredLabel("Scaled"),
        centeredLabel("Resampled")
    );
    layout.setAlignment(Pos.CENTER);
    
    layout.setStyle("-fx-background-color: cornsilk; -fx-padding: 10;");
    stage.setScene(
      new Scene(layout)
    );
    stage.show();
  }
  
  private Node withTooltip(Node node, String text) {
    Tooltip.install(node, new Tooltip(text));
    return node;
  }
  
  private Label centeredLabel(String text) {
    Label label = new Label(text);
    GridPane.setHalignment(label, HPos.CENTER);

    return label;
  }
  
  private Image resample(Image input, int scaleFactor) {
    final int W = (int) input.getWidth();
    final int H = (int) input.getHeight();
    final int S = scaleFactor;
    
    WritableImage output = new WritableImage(
      W * S,
      H * S
    );
    
    PixelReader reader = input.getPixelReader();
    PixelWriter writer = output.getPixelWriter();
    
    for (int y = 0; y < H; y++) {
      for (int x = 0; x < W; x++) {
        final int argb = reader.getArgb(x, y);
        for (int dy = 0; dy < S; dy++) {
          for (int dx = 0; dx < S; dx++) {
            writer.setArgb(x * S + dx, y * S + dy, argb);
          }
        }
      }
    }
    
    return output;
  }
  
  public static void main(String[] args) { Application.launch(args); }
}

Answer to StackOverflow question: JavaFX ImageView without any smoothing

Among these and the default one (i.e. the smoothing that JavaFX does), which one has the fastest rendering?

Still works 10 years later with OpenFX 17

https://openjfx.io/javadoc/17/javafx.graphics/javafx/scene/image/package-summary.html