75dfa6a6fb
Add packJPG filter for Jpeg files (not active yet). Directory format changes for clarity.
54 lines
1.6 KiB
C
54 lines
1.6 KiB
C
/*
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* This file is a part of Pcompress, a chunked parallel multi-
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* algorithm lossless compression and decompression program.
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*
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* Copyright (C) 2012-2013 Moinak Ghosh. All rights reserved.
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* Use is subject to license terms.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 3 of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program.
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* If not, see <http://www.gnu.org/licenses/>.
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*
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* moinakg@belenix.org, http://moinakg.wordpress.com/
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*/
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#include "transpose.h"
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/*
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* Perform a simple matrix transpose of the given buffer in "from".
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* If the buffer contains tables of numbers or structured data a
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* transpose can potentially help improve compression ratio by
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* bringing repeating values in columns into row ordering.
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*/
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void
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transpose(unsigned char *from, unsigned char *to, uint64_t buflen, uint64_t stride, rowcol_t rc)
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{
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uint64_t rows, cols, i, j, k, l;
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if (rc == ROW) {
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rows = buflen / stride;
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cols = stride;
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} else {
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cols = buflen / stride;
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rows = stride;
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}
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k = 0;
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for (j = 0; j < rows; j++) {
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l = 0;
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for (i = 0; i < cols; i++) {
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to[j + l] = from[i + k];
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l += rows;
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}
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k += cols;
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}
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}
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