tjGetScaledSize() would never be able to accommodate scaling factors > 1, so replace it with a function that returns a list of fractional scaling factors that TurboJPEG supports.

java/org/libjpegturbo/turbojpeg/TJ.java

@@ -30,6 +30,11 @@ package org.libjpegturbo.turbojpeg;
 
 final public class TJ {
 
+  final public class ScalingFactor {
+    public int num = 1;
+    public int denom = 1;
+  };
+
   // Chrominance subsampling options
   final public static int
     NUMSAMPOPT = 4,
@@ -105,6 +110,9 @@ final public class TJ {
     int subsamp)
     throws Exception;
 
+  public native final static ScalingFactor [] getScalingFactors()
+    throws Exception;
+
   static {
     System.loadLibrary("turbojpeg");
   }