Question

I am making an image editing like program, and when I want to edit large images it really starts to slow down. What is a good way to edit large image quickly? This example adjusts the image’s brightness, it works, but when I get large images such as 3456×2304 its really slow.

I have a slider, which calls this function every time it moves.

// Slider in a dialog box
private void sldBrightnessStateChanged(javax.swing.event.ChangeEvent evt) {
    // Get the position of the slider
    int val = sldBrightness.getValue();
    // Set the text in the textbox
    txtBrightness.setText("" + val);
    // New Brightness class (see below)
    Brightness adjustment = new Brightness();
    adjustment.amount(val);
    adjustment.applyFilter();
    // get the result built by applyFilter();
    Canvas.preview = Preview.getImage();
    // Update main program
    this.getParent().repaint();
}

Then the filter:

package pocketshop.graphics.adjustments;

import java.awt.image.BufferedImage;
import pocketshop.Canvas;
import pocketshop.graphics.Colors;
import pocketshop.graphics.Preview;

public class Brightness{

    protected int amount = 0;

    public void amount(int amount){
        this.amount = amount;
    }

    public void applyFilter(){
        int width = Canvas.image.getWidth();
        int height = Canvas.image.getHeight();
        int[] pixels = new int[width * height];

        Canvas.image.getRGB(0, 0, width, height, pixels, 0, width);
        for(int i = 0; i < pixels.length; i++){
            int pixel = pixels[i];
            //int pixel = Canvas.image.getRGB(x, y);
            int red = Colors.red(pixel);
            int green = Colors.green(pixel);
            int blue = Colors.blue(pixel);

            red += amount;
            if(red > 255){
                red = 255;
            }else if(red < 0){
                red = 0;
            }

            green += amount;
            if(green > 255){
                green = 255;
            }else if(green < 0){
                green = 0;
            }

            blue += amount;
            if(blue > 255){
                blue = 255;
            }else if(blue < 0){
                blue = 0;
            }
            pixels[i] = Colors.rgba(red, green, blue);
        }
        //BrightnessContrastDialog.preview.setRGB(0, 0, width, height, pixels, 0, width);
        BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
        img.setRGB(0, 0, width, height, pixels, 0, width);
        Preview.setImage(img);
    }
}

Answer 1

As I understand the picture is presented for user in order to give immediate feedback of changes that are made, what you can do us display downsampled version of picture and perform the brightness change to it while slider is moving which will be fast. Once user is satisfied with the value she selected using slider you can apply the change to original image. You can add apply button or something