compress example: --transformation argument

Note that the examples must not be called from the project root, because
then the root's blosc2_openhtj2k will be picked up, instead of the one
installed.

examples/compress.py

@@ -11,8 +11,14 @@
 # This is done once.
 blosc2.register_codec("openhtj2k", 244)
 
-def compress(im, urlpath=None):
-    """This function gets a PIL image and returns a blosc2 array.
+def compress(im, urlpath=None, **kwargs):
+    """
+    This function gets a PIL image and returns a Blosc2 array.
+
+    If the optional argument urlpath is given, the Blosc2 array will be saved to that
+    location.
+
+    Other keyword arguments are passed to blosc2_openhtj2k.set_params_defaults(...)
     """
     # Convert the image to a numpy array
     np_array = np.asarray(im)
@@ -28,9 +34,7 @@ def compress(im, urlpath=None):
     np_array = np_array.astype('uint32')
 
     # Set the parameters that will be used by the codec
-    blosc2_openhtj2k.set_params_defaults(
-        transformation=0,   # 0:lossy 1:lossless (default is 1)
-    )
+    blosc2_openhtj2k.set_params_defaults(**kwargs)
 
     # Multithreading is not supported, so we must set the number of threads to 1
     nthreads = 1
@@ -68,8 +72,11 @@ def compress(im, urlpath=None):
     )
     parser.add_argument('inputfile')
     parser.add_argument('outputfile')
+    parser.add_argument('--transformation', type=int, help='0:lossy 1:lossless (default is 1)')
     args = parser.parse_args()
 
+    kwargs = {k: v for k, v in args._get_kwargs() if k in blosc2_openhtj2k.params_defaults}
+
     im = Image.open(args.inputfile)
     Path(args.outputfile).unlink(missing_ok=True)
-    compress(im, args.outputfile)
+    compress(im, args.outputfile, **kwargs)

src/blosc2_htj2k.cpp

@@ -278,8 +278,6 @@ int blosc2_openhtj2k_decoder(
 }
 
 
-
-
 int set_params_defaults(
   uint8_t qfactor,
   bool isJPH,

src/test_j2k.c

@@ -27,8 +27,8 @@
 #include "utils.h"
 
 #define BLOSC_CODEC_OPENHTJ2K 244
-#define IFNAME "examples/teapot.ppm"
-#define OFNAME "examples/teapot2.ppm"
+#define IFNAME "teapot.ppm"
+#define OFNAME "/tmp/teapot2.ppm"
 
 /* Helper function to register the codec */
 void openhtj2k_register(blosc2_codec *codec) {