Fixed Issue 196: Utility method to create thumbnails

Incorporated excellent patch from Romain Guy for creating high-quality
thumbnails.


git-svn-id: file:///usr/local/projects/SUN/JOGL/git-svn/svn-server-sync/jogl/trunk@565 232f8b59-042b-4e1e-8c03-345bb8c30851

1 files changed, 62 insertions, 0 deletions

diff --git a/src/classes/com/sun/opengl/util/ImageUtil.java b/src/classes/com/sun/opengl/util/ImageUtil.java
index 1ce77fecf..f8981bd36 100755
--- a/src/classes/com/sun/opengl/util/ImageUtil.java
+++ b/src/classes/com/sun/opengl/util/ImageUtil.java
@@ -39,6 +39,7 @@
 
 package com.sun.opengl.util;
 
+import java.awt.*;
 import java.awt.image.*;
 
 /** Utilities for dealing with images. */
@@ -61,4 +62,65 @@ public class ImageUtil {
       raster.setDataElements(0, image.getHeight() - i - 1, image.getWidth(), 1, scanline1);
     }
   }
+
+  /**
+   * Creates a <code>BufferedImage</code> with a pixel format compatible with the graphics
+   * environment. The returned image can thus benefit from hardware accelerated operations
+   * in Java2D API.
+   *
+   * @param width The width of the image to be created
+   * @param height The height of the image to be created
+   *
+   * @return A instance of <code>BufferedImage</code> with a type compatible with the graphics card.
+   */
+  public static BufferedImage createCompatibleImage(int width, int height) {
+    GraphicsConfiguration configuration =
+      GraphicsEnvironment.getLocalGraphicsEnvironment().
+      getDefaultScreenDevice().getDefaultConfiguration();
+    return configuration.createCompatibleImage(width, height);
+  }
+
+  /**
+   * Creates a thumbnail from an image. A thumbnail is a scaled down version of the original picture.
+   * This method will retain the width to height ratio of the original picture and return a new
+   * instance of <code>BufferedImage</code>. The original picture is not modified.
+   *
+   * @param image The original image to sample down
+   * @param thumbWidth The width of the thumbnail to be created
+   *
+   * @throws IllegalArgumentException If thumbWidth is greater than image.getWidth()
+   *
+   * @return A thumbnail with the requested width or the original picture if thumbWidth = image.getWidth()
+   */
+  public static BufferedImage createThumbnail(BufferedImage image, int thumbWidth) {
+    // Thanks to Romain Guy for this utility
+    if (thumbWidth > image.getWidth()) {
+      throw new IllegalArgumentException("Thumbnail width must be greater than image width");
+    }
+   
+    if (thumbWidth == image.getWidth()) {
+      return image;
+    }
+ 
+    float ratio = (float) image.getWidth() / (float) image.getHeight();
+    int width = image.getWidth();
+    BufferedImage thumb = image;
+   
+    do {
+      width /= 2;
+      if (width < thumbWidth) {
+        width = thumbWidth;
+      }
+     
+      BufferedImage temp = createCompatibleImage(width, (int) (width / ratio));
+      Graphics2D g2 = temp.createGraphics();
+      g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
+                          RenderingHints.VALUE_INTERPOLATION_BILINEAR);
+      g2.drawImage(thumb, 0, 0, temp.getWidth(), temp.getHeight(), null);
+      g2.dispose();
+      thumb = temp;
+    } while (width != thumbWidth);
+   
+    return thumb;
+  }
 }