TJCompressor.compress(int): Fix YUV-to-JPEG error

Due to an oversight, the TJCompressor.compress(int) method did not
handle YUV source images.

Fixes #413

ChangeLog.md

@@ -8,6 +8,11 @@ in the MIPS DSPr2 SIMD extensions are now disabled until/unless they can be
 fixed, and other functions that are incompatible with big endian MIPS CPUs are
 disabled when building libjpeg-turbo for such CPUs.
 
+2. Fixed an oversight in the `TJCompressor.compress(int)` method in the
+TurboJPEG Java API that caused an error ("java.lang.IllegalStateException: No
+source image is associated with this instance") when attempting to use that
+method to compress a YUV image.
+
 
 2.0.4
 =====

java/org/libjpegturbo/turbojpeg/TJCompressor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (C)2011-2015, 2018 D. R. Commander.  All Rights Reserved.
+ * Copyright (C)2011-2015, 2018, 2020 D. R. Commander.  All Rights Reserved.
  * Copyright (C)2015 Viktor Szathmáry.  All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -377,8 +377,15 @@ public class TJCompressor implements Closeable {
    * #getCompressedSize} to obtain the size of the JPEG image.
    */
   public byte[] compress(int flags) throws TJException {
-    checkSourceImage();
-    byte[] buf = new byte[TJ.bufSize(srcWidth, srcHeight, subsamp)];
+    byte[] buf;
+    if (srcYUVImage != null) {
+      buf = new byte[TJ.bufSize(srcYUVImage.getWidth(),
+                                srcYUVImage.getHeight(),
+                                srcYUVImage.getSubsamp())];
+    } else {
+      checkSourceImage();
+      buf = new byte[TJ.bufSize(srcWidth, srcHeight, subsamp)];
+    }
     compress(buf, flags);
     return buf;
   }