libjpeg-turbo-1.2.1-tiff-ojpeg

[platform/upstream/libjpeg-turbo.git] / jdhuff.c

diff --git a/jdhuff.c b/jdhuff.c
index dba5f18..7894c84 100644 (file)
--- a/jdhuff.c
+++ b/jdhuff.c
@@ -807,3 +807,35 @@ jinit_huff_decoder (j_decompress_ptr cinfo)
     entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
   }
 }
+/*
+ * BEWARE OF KLUDGE:  This subroutine is a hack for decoding illegal JPEG-in-
+ *                    TIFF encapsulations produced by Microsoft's Wang Imaging
+ * for Windows application with the public-domain TIFF Library.  Based upon an
+ * examination of selected output files, this program apparently divides a JPEG
+ * bit-stream into consecutive horizontal TIFF "strips", such that the JPEG
+ * encoder's/decoder's DC coefficients for each image component are reset before
+ * each "strip".  Moreover, a "strip" is not necessarily encoded in a multiple
+ * of 8 bits, so one must sometimes discard 1-7 bits at the end of each "strip"
+ * for alignment to the next input-Byte storage boundary.  IJG JPEG Library
+ * decoder state is not normally exposed to client applications, so this sub-
+ * routine provides the TIFF Library with a "hook" to make these corrections.
+ * It should be called after "jpeg_start_decompress()" and before
+ * "jpeg_finish_decompress()", just before decoding each "strip" using
+ * "jpeg_read_raw_data()" or "jpeg_read_scanlines()".
+ *
+ * This kludge is not sanctioned or supported by the Independent JPEG Group, and
+ * future changes to the IJG JPEG Library might invalidate it.  Do not send bug
+ * reports about this code to IJG developers.  Instead, contact the author for
+ * advice: Scott B. Marovich <marovich@hpl.hp.com>, Hewlett-Packard Labs, 6/01.
+ */
+GLOBAL(void)
+jpeg_reset_huff_decode (register j_decompress_ptr cinfo,register float *refbw)
+{ register huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
+  register int ci = 0;
+
+  /* Re-initialize DC predictions */
+  do entropy->saved.last_dc_val[ci] = -refbw[ci << 1];
+  while (++ci < cinfo->comps_in_scan);
+  /* Discard encoded input bits, up to the next Byte boundary */
+  entropy->bitstate.bits_left &= ~7;
+}