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Semester 1/Programming 1/Java/examples/projects/chapter13/imageviewer0-4/ImageFileManager.java

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+import java.awt.image.*;
+import javax.imageio.*;
+import javax.swing.*;
+import java.io.*;
+
+/**
+ * ImageFileManager is a small utility class with static methods to load
+ * and save images.
+ * 
+ * The files on disk can be in JPG or PNG image format. For files written
+ * by this class, the format is determined by the constant IMAGE_FORMAT.
+ * 
+ * @author Michael Kölling and David J. Barnes.
+ * @version 1.0
+ */
+public class ImageFileManager
+{
+    // A constant for the image format that this writer uses for writing.
+    // Available formats are "jpg" and "png".
+    private static final String IMAGE_FORMAT = "jpg";
+    private static JFileChooser fileChooser = new JFileChooser(System.getProperty("user.dir"));
+    
+    /**
+     * Open a file chooser and let the user select an image file in the file
+     * system. Then read an image file from disk and return it as an image. This method
+     * can read JPG and PNG file formats. In case of any problem (e.g the file does
+     * not exist, is in an undecodable format, or any other read error) this method
+     * returns null.
+     * 
+     * @return       The image object or null is it was not a valid image file.
+     */
+    public static OFImage getImage()
+    {
+        int returnVal = fileChooser.showOpenDialog(null);
+
+        if(returnVal != JFileChooser.APPROVE_OPTION) {
+            return null;  // cancelled
+        }
+        File selectedFile = fileChooser.getSelectedFile();
+        return loadImage(selectedFile);
+    }
+
+    /**
+     * Read an image file from disk and return it as a BufferedImage. This method
+     * can read JPG and PNG file formats. In case of any problem (e.g the file does
+     * not exist, is in an undecodable format, or any other read error) this method
+     * returns null.
+     * 
+     * @param imageFile  The image file to be loaded.
+     * @return           The image object or null if it was not a valid image file.
+     */
+    public static OFImage loadImage(File imageFile)
+    {
+        try {
+            BufferedImage image = ImageIO.read(imageFile);
+            if(image == null || (image.getWidth(null) < 0)) {
+                // we could not load the image - probably invalid file format
+                return null;
+            }
+            return new OFImage(image);
+        }
+        catch(IOException exc) {
+            return null;
+        }
+    }
+
+    /**
+     * Write an image file to disk. The file format is JPG. In case of any problem
+     * the method just silently returns.
+     * 
+     * @param image  The image to be saved.
+     * @param file   The file to save to.
+     */
+    public static void saveImage(OFImage image, File file)
+    {
+        try {
+            ImageIO.write(image, IMAGE_FORMAT, file);
+        }
+        catch(IOException exc) {
+            return;
+        }
+    }
+}