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, 20 insertions, 0 deletions

diff --git a/src/lib/openjp2/jp2.c b/src/lib/openjp2/jp2.c
index 84d39327..81d03480 100644
--- a/src/lib/openjp2/jp2.c
+++ b/src/lib/openjp2/jp2.c
@@ -1607,6 +1607,11 @@ OPJ_BOOL opj_jp2_decode(opj_jp2_t *jp2,
         return OPJ_FALSE;
     }
 
+    if (jp2->j2k->m_specific_param.m_decoder.m_numcomps_to_decode) {
+        /* Bypass all JP2 component transforms */
+        return OPJ_TRUE;
+    }
+
     if (!jp2->ignore_pclr_cmap_cdef) {
         if (!opj_jp2_check_color(p_image, &(jp2->color), p_manager)) {
             return OPJ_FALSE;
@@ -3069,6 +3074,16 @@ void opj_jp2_destroy(opj_jp2_t *jp2)
     }
 }
 
+OPJ_BOOL opj_jp2_set_decoded_components(opj_jp2_t *p_jp2,
+                                        OPJ_UINT32 numcomps,
+                                        const OPJ_UINT32* comps_indices,
+                                        opj_event_mgr_t * p_manager)
+{
+    return opj_j2k_set_decoded_components(p_jp2->j2k,
+                                          numcomps, comps_indices,
+                                          p_manager);
+}
+
 OPJ_BOOL opj_jp2_set_decode_area(opj_jp2_t *p_jp2,
                                  opj_image_t* p_image,
                                  OPJ_INT32 p_start_x, OPJ_INT32 p_start_y,
@@ -3100,6 +3115,11 @@ OPJ_BOOL opj_jp2_get_tile(opj_jp2_t *p_jp2,
         return OPJ_FALSE;
     }
 
+    if (p_jp2->j2k->m_specific_param.m_decoder.m_numcomps_to_decode) {
+        /* Bypass all JP2 component transforms */
+        return OPJ_TRUE;
+    }
+
     if (!opj_jp2_check_color(p_image, &(p_jp2->color), p_manager)) {
         return OPJ_FALSE;
     }