Improve javaFx processing performance - image-processing

Question

I'm working on Image processing with javaFx. I think that my code is not enouth efficient (With HD images, refresh is very slow). Because I do a for on each pixel of my image everytime I have to refresh it. But I don't know how to do differently.
So I need help to improve the performance of my processing.
This is my code :
import javafx.application.Application;
import javafx.beans.InvalidationListener;
import javafx.beans.Observable;
import javafx.beans.property.DoubleProperty;
import javafx.scene.Scene;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.Slider;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.image.PixelReader;
import javafx.scene.image.PixelWriter;
import javafx.scene.image.WritableImage;
import javafx.scene.layout.AnchorPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
public class Example extends Application {
private Image src;
private WritableImage dest;
private int width;
private int height;
int value = 0;
#Override
public void start(Stage stage) {
AnchorPane root = new AnchorPane();
initImage(root);
Scene scene = new Scene(root);
stage.setTitle("Demo processing");
stage.setResizable(false);
stage.setScene(scene);
stage.show();
}
private void initImage(AnchorPane root) {
src = new Image(
"http://mikecann.co.uk/wp-content/uploads/2009/12/ScreenHunter_02-Dec.-10-19.41-1024x484.jpg");
width = (int) src.getWidth();
height = (int) src.getHeight();
root.setPrefSize(800, 800 + 50);
ScrollPane scrollPane = new ScrollPane();
scrollPane.setPrefHeight(600);
scrollPane.setPrefWidth(1000);
dest = new WritableImage(width, height);
ImageView destView = new ImageView(dest);
scrollPane.setContent(destView);
root.getChildren().add(scrollPane);
AnchorPane.setTopAnchor(scrollPane, 0.0);
Slider slider = new Slider(0, 255, 1);
slider.setPrefSize(800, 50);
slider.setShowTickLabels(true);
slider.setShowTickMarks(true);
slider.setSnapToTicks(true);
slider.setMajorTickUnit(1.0);
slider.setMinorTickCount(0);
slider.setLayoutY(700);
slider.valueProperty().addListener(new InvalidationListener() {
#Override
public void invalidated(Observable o) {
value = (int) ((DoubleProperty) o).get();
color();
}
});
root.getChildren().add(slider);
color();
}
private void color() {
PixelReader reader = src.getPixelReader();
PixelWriter writer = dest.getPixelWriter();
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
Color color = reader.getColor(x, y);
double red = (double) value * x * y / (width * height) / 255;
double green = color.getGreen();
double blue = (double) value * ((width * height) - x * y)
/ (width * height) / 255;
writer.setColor(x, y, Color.color(red, green, blue));
}
}
}
public static void main(String[] args) {
launch(args);
}
}
And this is with a full HD image :
src = new Image(
"http://www.freedomwallpaper.com//nature-wallpaper-hd/hd_sunshine_hd.jpg");

Answer 1

Getitng color of each pixel in loop is too slow. So, get entire pixels first, and change colors, finally wirte changed colors with PixelWriter.
Like this
private void color() {
PixelReader reader = src.getPixelReader();
WritablePixelFormat<IntBuffer> format = WritablePixelFormat.getIntArgbInstance();
int[] pixels = new int[width * height]; // Buffer for all pixels
reader.getPixels(0, 0, width, height, format, pixels, 0, width); // get all pixels by argb format
int alpha = 0xFF << 24;
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
int index = x + y * width;
int argb = pixels[index];
int red = value * x * y / (width * height);
int green = (argb >> 8) & 0xFF;
int blue = value * ((width * height) - x * y)
/ (width * height);
int newArgb = alpha | (red << 16) | (green << 8) | blue;
pixels[index] = newArgb;
}
}
PixelWriter writer = dest.getPixelWriter();
writer.setPixels(0, 0, width, height, format, pixels, 0, width); // write entire image
}