praktikum-holons/src/holeg/ui/view/image/Import.java

package holeg.ui.view.image;

import java.awt.Image;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import javax.imageio.ImageIO;

import holeg.preferences.ImagePreference;

/**
 * 
 * @author TU-Darmstadt BP Gruppe 7 WS17/18 Centralized resource loading methods
 *         for improved performance and easier troubleshooting.
 */
public class Import {
	/*
	 * Save nothing: Reload every image whenever requested. Save external: Only save
	 * images that were found as external file. Save raw: Save all non-scaled
	 * images. Save everything: self-explanatory.
	 */
	private static HashMap<String, Image> imgStorage;
	private static Import xmp = new Import();// Used to load resources from the JAR.

	static {
		imgStorage = new HashMap<String, Image>();
	}

	/**
	 * The rawest function replacing the old method without any default parameters.
	 * Currently not used in HOLEG at all(aside form calls from the convenience
	 * methods).
	 * 
	 * @param url   Path to the image to be loaded.
	 * @param w     Width the loaded image should be scaled to.
	 * @param h     Height the loaded image should be scaled to.
	 * @param hints Hints for the scaling algorithm to be used. Same as the
	 *              parameter in the getScaledInstance function of Image.
	 * @return A loaded and scaled image from the requested path.
	 */
	static Image loadImage(String url, int w, int h, int hints) {
		String key = url + "?" + w + "?" + h + "?" + hints;
		if (imgStorage.containsKey(key))
			return (imgStorage.get(key));
		else {
			Image img = loadImage(url).getScaledInstance(w, h, hints);
			imgStorage.put(key, img);
			return img;
		}
	}

	/**
	 * Loads an image from the given path and scales it using the smooth algorithm.
	 * 
	 * @param url Path to the image to be loaded.
	 * @param w   Width the loaded image should be scaled to.
	 * @param h   Height the loaded image should be scaled to.
	 * @return A loaded and (smoothly) scaled image from the requested path.
	 */
	public static Image loadImage(String url, int w, int h) {
		return loadImage(url, w, h, Image.SCALE_SMOOTH);
	}

	/**
	 * Loads an image from the given path and scales it using the smooth algorithm.
	 * 
	 * @param url Path to the image to be loaded.
	 * @return An image loaded from the requested path.
	 */
	public static Image loadImage(String url) {
		if (imgStorage.containsKey(url))
			return imgStorage.get(url);
		else {
			Image img;
			try {
				img = ImageIO.read(loadStream(url));
			} catch (IOException e) {
				return new BufferedImage(0, 0,
						BufferedImage.TYPE_INT_RGB);
			}
			imgStorage.put(url, img);
			return img;
		}
	}

	/**
	 * Loads any resource with a given path, regardless of whether it is inside the
	 * jar or an external resource. Every loadImage() function uses this as a basis.
	 * 
	 * @param url The path (and file name) of the requested resource.
	 * @return An InputStream from the requested resource.
	 * @throws FileNotFoundException
	 */
	public static InputStream loadStream(String url) throws FileNotFoundException {
		InputStream o = xmp.getClass().getResourceAsStream(url);
		if (o != null)
			return o;
		else {
			boolean rootSymbol = switch (url.charAt(0)) { // So we can make sure to construct res/path correctly.
				case '/', '\\' -> true;
				default -> false; // Whether url starts with a / or \
			};
			File f = new File(url);
			if (!f.exists()) {
				url = "res" + (rootSymbol ? "" : "/") + url;
			}
			f = new File(url);// Possible bug with duplicate names.
			if (!f.exists()) {
				url = "res" + ImagePreference.Canvas.ImageNotFound;
			}
			return new FileInputStream(url);

		}
	}

	// Nobody needs an instance of this. I do, because I use it to load images from
	// inside the JAR.
	private Import() {
	}
}