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The SBDSOFFSET field is a *signed* 5 bit integer, so we need to sign 
extend when reading the field to get the proper value. We now correctly
handle the 042_20.jb2 test stream.


git-svn-id: http://svn.ghostscript.com/jbig2dec/trunk@442 ded80894-8fb9-0310-811b-c03f3676ab4d

--- a/jbig2_text.c

+++ b/jbig2_text.c

@@ -494,6 +494,9 @@

     /* 7.4.3.1.1 */

     flags = jbig2_get_int16(segment_data + offset);

     offset += 2;

+

+    jbig2_error(ctx, JBIG2_SEVERITY_DEBUG, segment->number,

+	"text region header flags 0x%04x", flags);

     params.SBHUFF = flags & 0x0001;

     params.SBREFINE = flags & 0x0002;

@@ -503,8 +506,15 @@

     params.TRANSPOSED = flags & 0x0040;

     params.SBCOMBOP = (flags & 0x0180) >> 7;

     params.SBDEFPIXEL = flags & 0x0200;

+    /* SBDSOFFSET is a signed 5 bit integer */

     params.SBDSOFFSET = (flags & 0x7C00) >> 10;

+    if (params.SBDSOFFSET > 0x0f) params.SBDSOFFSET -= 0x20;

     params.SBRTEMPLATE = flags & 0x8000;

+

+    if (params.SBDSOFFSET) {

+      jbig2_error(ctx, JBIG2_SEVERITY_DEBUG, segment->number,

+	"text region has SBDSOFFSET %d", params.SBDSOFFSET);

+    }

     if (params.SBHUFF)	/* Huffman coding */

       {