jpeg2000: Compute corrections of sub-band coordinates

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavcodec/jpeg2000.c

@@ -335,9 +335,8 @@ int ff_jpeg2000_init_component(Jpeg2000Component *comp,
                 for (i = 0; i < 2; i++)
                     for (j = 0; j < 2; j++)
                         band->coord[i][j] =
-                            ff_jpeg2000_ceildivpow2(comp->coord_o[i][j],
+                            ff_jpeg2000_ceildivpow2(comp->coord_o[i][j] - comp->coord_o[i][0],
                                                     declvl - 1);
-
                 log2_band_prec_width  = reslevel->log2_prec_width;
                 log2_band_prec_height = reslevel->log2_prec_height;
                 /* see ISO/IEC 15444-1:2002 eq. B-17 and eq. B-15 */
@@ -352,7 +351,7 @@ int ff_jpeg2000_init_component(Jpeg2000Component *comp,
                     for (j = 0; j < 2; j++)
                         /* Formula example for tbx_0 = ceildiv((tcx_0 - 2 ^ (declvl - 1) * x0_b) / declvl) */
                         band->coord[i][j] =
-                            ff_jpeg2000_ceildivpow2(comp->coord_o[i][j] -
+                            ff_jpeg2000_ceildivpow2(comp->coord_o[i][j] - comp->coord_o[i][0] -
                                                     (((bandno + 1 >> i) & 1) << declvl - 1),
                                                     declvl);
                 /* TODO: Manage case of 3 band offsets here or
@@ -368,6 +367,11 @@ int ff_jpeg2000_init_component(Jpeg2000Component *comp,
                 log2_band_prec_height = reslevel->log2_prec_height - 1;
             }
 
+            for (j = 0; j < 2; j++)
+                band->coord[0][j] = ff_jpeg2000_ceildiv(band->coord[0][j], dx);
+            for (j = 0; j < 2; j++)
+                band->coord[1][j] = ff_jpeg2000_ceildiv(band->coord[1][j], dy);
+
             band->prec = av_malloc_array(reslevel->num_precincts_x *
                                          reslevel->num_precincts_y,
                                          sizeof(*band->prec));