Back-port code from jpeg-8 that removes unpopulated (and unneeded) tables for AC and DC coefficients when generating progressive JPEG files with arithmetic coding. This should make such files bitwise compatible with jpeg-8, barring any other mathematical differences listed in README-turbo.txt. Add regression tests for progressive+arithmetic JPEG files.

git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.3.x@1080 632fc199-4ca6-4c93-a231-07263d6284db

1 files changed, 35 insertions, 42 deletions

diff --git a/jcmarker.c b/jcmarker.c
index 57c247c..4fbece4 100644
--- a/jcmarker.c
+++ b/jcmarker.c
@@ -239,26 +239,32 @@ emit_dac (j_compress_ptr cinfo)
 
   for (i = 0; i < cinfo->comps_in_scan; i++) {
     compptr = cinfo->cur_comp_info[i];
-    dc_in_use[compptr->dc_tbl_no] = 1;
-    ac_in_use[compptr->ac_tbl_no] = 1;
+    /* DC needs no table for refinement scan */
+    if (cinfo->Ss == 0 && cinfo->Ah == 0)
+      dc_in_use[compptr->dc_tbl_no] = 1;
+    /* AC needs no table when not present */
+    if (cinfo->Se)
+      ac_in_use[compptr->ac_tbl_no] = 1;
   }
 
   length = 0;
   for (i = 0; i < NUM_ARITH_TBLS; i++)
     length += dc_in_use[i] + ac_in_use[i];
-  
-  emit_marker(cinfo, M_DAC);
-  
-  emit_2bytes(cinfo, length*2 + 2);
-  
-  for (i = 0; i < NUM_ARITH_TBLS; i++) {
-    if (dc_in_use[i]) {
-      emit_byte(cinfo, i);
-      emit_byte(cinfo, cinfo->arith_dc_L[i] + (cinfo->arith_dc_U[i]<<4));
-    }
-    if (ac_in_use[i]) {
-      emit_byte(cinfo, i + 0x10);
-      emit_byte(cinfo, cinfo->arith_ac_K[i]);
+
+  if (length) {
+    emit_marker(cinfo, M_DAC);
+
+    emit_2bytes(cinfo, length*2 + 2);
+
+    for (i = 0; i < NUM_ARITH_TBLS; i++) {
+      if (dc_in_use[i]) {
+	emit_byte(cinfo, i);
+	emit_byte(cinfo, cinfo->arith_dc_L[i] + (cinfo->arith_dc_U[i]<<4));
+      }
+      if (ac_in_use[i]) {
+	emit_byte(cinfo, i + 0x10);
+	emit_byte(cinfo, cinfo->arith_ac_K[i]);
+      }
     }
   }
 #endif /* C_ARITH_CODING_SUPPORTED */
@@ -324,22 +330,16 @@ emit_sos (j_compress_ptr cinfo)
   for (i = 0; i < cinfo->comps_in_scan; i++) {
     compptr = cinfo->cur_comp_info[i];
     emit_byte(cinfo, compptr->component_id);
-    td = compptr->dc_tbl_no;
-    ta = compptr->ac_tbl_no;
-    if (cinfo->progressive_mode) {
-      /* Progressive mode: only DC or only AC tables are used in one scan;
-       * furthermore, Huffman coding of DC refinement uses no table at all.
-       * We emit 0 for unused field(s); this is recommended by the P&M text
-       * but does not seem to be specified in the standard.
-       */
-      if (cinfo->Ss == 0) {
-	ta = 0;			/* DC scan */
-	if (cinfo->Ah != 0 && !cinfo->arith_code)
-	  td = 0;		/* no DC table either */
-      } else {
-	td = 0;			/* AC scan */
-      }
-    }
+
+    /* We emit 0 for unused field(s); this is recommended by the P&M text
+     * but does not seem to be specified in the standard.
+     */
+
+    /* DC needs no table for refinement scan */
+    td = cinfo->Ss == 0 && cinfo->Ah == 0 ? compptr->dc_tbl_no : 0;
+    /* AC needs no table when not present */
+    ta = cinfo->Se ? compptr->ac_tbl_no : 0;
+
     emit_byte(cinfo, (td << 4) + ta);
   }
 
@@ -573,19 +573,12 @@ write_scan_header (j_compress_ptr cinfo)
      */
     for (i = 0; i < cinfo->comps_in_scan; i++) {
       compptr = cinfo->cur_comp_info[i];
-      if (cinfo->progressive_mode) {
-	/* Progressive mode: only DC or only AC tables are used in one scan */
-	if (cinfo->Ss == 0) {
-	  if (cinfo->Ah == 0)	/* DC needs no table for refinement scan */
-	    emit_dht(cinfo, compptr->dc_tbl_no, FALSE);
-	} else {
-	  emit_dht(cinfo, compptr->ac_tbl_no, TRUE);
-	}
-      } else {
-	/* Sequential mode: need both DC and AC tables */
+      /* DC needs no table for refinement scan */
+      if (cinfo->Ss == 0 && cinfo->Ah == 0)
 	emit_dht(cinfo, compptr->dc_tbl_no, FALSE);
+      /* AC needs no table when not present */
+      if (cinfo->Se)
 	emit_dht(cinfo, compptr->ac_tbl_no, TRUE);
-      }
     }
   }