Solving the quality problem when resizing. It costs a bit in CPU usage, but worth it.

photos/geiranger/.cvsignore

@@ -0,0 +1 @@
+cache.properties

src/org/forkalsrud/album/exif/Dimension.java

@@ -16,6 +16,11 @@ public class Dimension {
     int w;
     int h;
 
+    public Dimension(Dimension other) {
+    	this.w = other.w;
+    	this.h = other.h;
+    }
+
     public Dimension(int w, int h) {
         this.w = w;
         this.h = h;
@@ -28,6 +33,16 @@ public class Dimension {
     }
 
 
+    public Dimension doubled() {
+
+    	return new Dimension(w * 2, h * 2);
+    }
+
+    public Dimension halved() {
+
+    	return new Dimension(w / 2, h / 2);
+    }
+
     public Dimension scaled(int max) {
 
         return w > h ? scaleWidth(max) : scaleHeight(max);

src/org/forkalsrud/album/web/AlbumServlet.java

@@ -153,61 +153,69 @@ public class AlbumServlet
             outd = orig.scaled(worh);
         }
 
+        /* In order to make the quality as good as possible we follow the advice from
+         * http://today.java.net/pub/a/today/2007/04/03/perils-of-image-getscaledinstance.html
+         * and scale the image by a factor of 2 in intermediate steps, thereby getting a smoother
+         * end result.  The first scale will get to a size which is a multiple of the result size.
+         * the first scaling operation will also take care of any rotation that needs to happen.
+         */
+        Dimension intermediate = new Dimension(outd);
+        int targetWidth = orig.getWidth() / 2;
+        while (intermediate.getWidth() < targetWidth) {
+        	intermediate = intermediate.doubled();
+        }
+
         Iterator<ImageReader> readers = ImageIO.getImageReadersByFormatName("jpg");
         ImageReader reader = readers.next();
         ImageInputStream iis = ImageIO.createImageInputStream(file);
         reader.setInput(iis, true);
         ImageReadParam param = reader.getDefaultReadParam();
-//        param.setDestinationType(ImageTypeSpecifier.createFromBufferedImageType(BufferedImage.TYPE_INT_ARGB));
-        if (false /* subsampling */) {
-            double subSampleScale = (double)outd.getWidth() / orig.getWidth();
-            int subSampling = (int)Math.floor(0.25d/subSampleScale);
-            if (subSampling > 1) {
-                param.setSourceSubsampling(subSampling, subSampling, 0, 0);
-            }
-        }
         BufferedImage img = reader.read(0, param);
         
         // Recalculate scale after sub-sampling was applied
         double scale;
         AffineTransform xform;
         if (thumbnail.getOrientation() == 6) {
-            xform = AffineTransform.getTranslateInstance(outd.getWidth() / 2d, outd.getHeight() / 2d);
+            xform = AffineTransform.getTranslateInstance(intermediate.getWidth() / 2d, intermediate.getHeight() / 2d);
             xform.rotate(Math.PI / 2);
-            scale = (double)outd.getHeight() / img.getWidth();
+            scale = (double)intermediate.getHeight() / img.getWidth();
             xform.scale(scale, scale);
             xform.translate(-img.getWidth() / 2d, -img.getHeight() / 2d);
             
         } else {
-            scale = (double)outd.getWidth() / img.getWidth();
+            scale = (double)intermediate.getWidth() / img.getWidth();
             xform = AffineTransform.getScaleInstance(scale, scale);
         }
-//        AffineTransformOp operation = new AffineTransformOp(xform, AffineTransformOp.TYPE_BICUBIC);
-//        BufferedImage buf2 = operation.createCompatibleDestImage(img, img.getColorModel());
-        BufferedImage buf2 = new BufferedImage(outd.getWidth(), outd.getHeight(), img.getType());
-
-//        operation.filter(img, buf2);
 
+        BufferedImage buf2 = new BufferedImage(intermediate.getWidth(), intermediate.getHeight(), img.getType());
         Graphics2D g2 = buf2.createGraphics();
-        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
+        g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
-        g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BICUBIC);
-        g2.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
-        g2.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
 
         g2.transform(xform);
         g2.drawImage(img, 0, 0, null);
 
+        while (intermediate.getWidth() > outd.getWidth()) {
+
+        	BufferedImage buf3 = buf2;
+        	intermediate = intermediate.halved();
+            buf2 = new BufferedImage(intermediate.getWidth(), intermediate.getHeight(), img.getType());
+            Graphics2D g3 = buf2.createGraphics();
+            g3.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
+            g3.drawImage(buf3, 0, 0, intermediate.getWidth(), intermediate.getHeight(), null);
+        }
+
         //        g2.drawImage(img, operation, 0, 0);
 
 
         Iterator<ImageWriter> writers = ImageIO.getImageWritersByFormatName("jpg");
         ImageWriter writer = writers.next();
-        ImageWriteParam wParam = writer.getDefaultWriteParam();
+//        ImageWriteParam wParam = writer.getDefaultWriteParam();
-        wParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
+//        wParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
-        wParam.setCompressionQuality(1.0f);
+//        wParam.setCompressionQuality(1.0f);
         ImageOutputStream ios = ImageIO.createImageOutputStream(res.getOutputStream());
         writer.setOutput(ios);
-        writer.write(null, new IIOImage(buf2, null, null), wParam);
+//        writer.write(null, new IIOImage(buf2, null, null), wParam);
+        writer.write(buf2);
     }