39 lines
1.9 KiB
Diff
39 lines
1.9 KiB
Diff
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--- a/jdhuff.c
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+++ b/jdhuff.c
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@@ -649,3 +649,35 @@
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entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
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}
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}
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+/*
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+ * BEWARE OF KLUDGE: This subroutine is a hack for decoding illegal JPEG-in-
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+ * TIFF encapsulations produced by Microsoft's Wang Imaging
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+ * for Windows application with the public-domain TIFF Library. Based upon an
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+ * examination of selected output files, this program apparently divides a JPEG
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+ * bit-stream into consecutive horizontal TIFF "strips", such that the JPEG
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+ * encoder's/decoder's DC coefficients for each image component are reset before
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+ * each "strip". Moreover, a "strip" is not necessarily encoded in a multiple
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+ * of 8 bits, so one must sometimes discard 1-7 bits at the end of each "strip"
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+ * for alignment to the next input-Byte storage boundary. IJG JPEG Library
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+ * decoder state is not normally exposed to client applications, so this sub-
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+ * routine provides the TIFF Library with a "hook" to make these corrections.
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+ * It should be called after "jpeg_start_decompress()" and before
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+ * "jpeg_finish_decompress()", just before decoding each "strip" using
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+ * "jpeg_read_raw_data()" or "jpeg_read_scanlines()".
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+ *
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+ * This kludge is not sanctioned or supported by the Independent JPEG Group, and
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+ * future changes to the IJG JPEG Library might invalidate it. Do not send bug
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+ * reports about this code to IJG developers. Instead, contact the author for
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+ * advice: Scott B. Marovich <marovich@hpl.hp.com>, Hewlett-Packard Labs, 6/01.
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+ */
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+GLOBAL(void)
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+jpeg_reset_huff_decode (register j_decompress_ptr cinfo,register float *refbw)
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+{ register huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
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+ register int ci = 0;
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+
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+ /* Re-initialize DC predictions */
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+ do entropy->saved.last_dc_val[ci] = -refbw[ci << 1];
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+ while (++ci < cinfo->comps_in_scan);
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+ /* Discard encoded input bits, up to the next Byte boundary */
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+ entropy->bitstate.bits_left &= ~7;
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+}
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