Add capability to decode only a subset of all components of an image.

This adds a opj_set_decoded_components(opj_codec_t *p_codec,
OPJ_UINT32 numcomps, const OPJ_UINT32* comps_indices) function,
and equivalent "opj_decompress -c compno[,compno]*" option.

When specified, neither the MCT transform nor JP2 channel transformations
will be applied.

Tests added for various combinations of whole image vs tiled-based decoding,
full or reduced resolution, use of decode area or not.

1 files changed, 19 insertions, 0 deletions

diff --git a/src/lib/openjp2/j2k.h b/src/lib/openjp2/j2k.h
index c9308f7d..b5fa5143 100644
--- a/src/lib/openjp2/j2k.h
+++ b/src/lib/openjp2/j2k.h
@@ -480,6 +480,10 @@ typedef struct opj_j2k_dec {
      * SOD reader function. FIXME NOT USED for the moment
      */
     OPJ_BOOL   m_last_tile_part;
+
+    OPJ_UINT32   m_numcomps_to_decode;
+    OPJ_UINT32  *m_comps_indices_to_decode;
+
     /** to tell that a tile can be decoded. */
     OPJ_BITFIELD m_can_decode : 1;
     OPJ_BITFIELD m_discard_tiles : 1;
@@ -705,6 +709,21 @@ OPJ_BOOL opj_j2k_read_tile_header(opj_j2k_t * p_j2k,
                                   opj_event_mgr_t * p_manager);
 
 
+/** Sets the indices of the components to decode.
+ *
+ * @param p_j2k         the jpeg2000 codec.
+ * @param numcomps      Number of components to decode.
+ * @param comps_indices Array of num_compts indices (numbering starting at 0)
+ *                      corresponding to the components to decode.
+ * @param p_manager     Event manager
+ *
+ * @return OPJ_TRUE in case of success.
+ */
+OPJ_BOOL opj_j2k_set_decoded_components(opj_j2k_t *p_j2k,
+                                        OPJ_UINT32 numcomps,
+                                        const OPJ_UINT32* comps_indices,
+                                        opj_event_mgr_t * p_manager);
+
 /**
  * Sets the given area to be decoded. This function should be called right after opj_read_header and before any tile header reading.
  *