33 lines
1.8 KiB
C
33 lines
1.8 KiB
C
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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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/* 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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