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* High quality image resampling with polyphase filters
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* Copyright (c) 2001 Gerard Lantau.
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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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
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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#include "fastmemcpy.h"
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#define NB_COMPONENTS 3
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#define NB_PHASES (1 << PHASE_BITS)
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#define FCENTER 1 /* index of the center of the filter */
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#define POS_FRAC_BITS 16
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#define POS_FRAC (1 << POS_FRAC_BITS)
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/* 6 bits precision is needed for MMX */
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#define LINE_BUF_HEIGHT (NB_TAPS * 4)
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struct ImgReSampleContext {
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int iwidth, iheight, owidth, oheight;
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INT16 h_filters[NB_PHASES][NB_TAPS] __align8; /* horizontal filters */
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INT16 v_filters[NB_PHASES][NB_TAPS] __align8; /* vertical filters */
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static inline int get_phase(int pos)
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return ((pos) >> (POS_FRAC_BITS - PHASE_BITS)) & ((1 << PHASE_BITS) - 1);
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/* This function must be optimized */
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static void h_resample_fast(UINT8 *dst, int dst_width, UINT8 *src, int src_width,
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int src_start, int src_incr, INT16 *filters)
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int src_pos, phase, sum, i;
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for(i=0;i<dst_width;i++) {
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if ((src_pos >> POS_FRAC_BITS) < 0 ||
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(src_pos >> POS_FRAC_BITS) > (src_width - NB_TAPS))
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s = src + (src_pos >> POS_FRAC_BITS);
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phase = get_phase(src_pos);
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filter = filters + phase * NB_TAPS;
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sum = s[0] * filter[0] +
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for(j=0;j<NB_TAPS;j++)
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sum += s[j] * filter[j];
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sum = sum >> FILTER_BITS;
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/* This function must be optimized */
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static void v_resample(UINT8 *dst, int dst_width, UINT8 *src, int wrap,
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for(i=0;i<dst_width;i++) {
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sum = s[0 * wrap] * filter[0] +
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s[1 * wrap] * filter[1] +
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s[2 * wrap] * filter[2] +
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s[3 * wrap] * filter[3];
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for(j=0;j<NB_TAPS;j++) {
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sum += s1[0] * filter[j];
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sum = sum >> FILTER_BITS;
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#include "i386/mmx.h"
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#define FILTER4(reg) \
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s = src + (src_pos >> POS_FRAC_BITS);\
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phase = get_phase(src_pos);\
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filter = filters + phase * NB_TAPS;\
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punpcklbw_r2r(mm7, reg);\
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movq_m2r(*filter, mm6);\
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pmaddwd_r2r(reg, mm6);\
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paddd_r2r(mm6, reg);\
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psrad_i2r(FILTER_BITS, reg);\
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src_pos += src_incr;\
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#define DUMP(reg) movq_r2m(reg, tmp); printf(#reg "=%016Lx\n", tmp.uq);
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/* XXX: do four pixels at a time */
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static void h_resample_fast4_mmx(UINT8 *dst, int dst_width, UINT8 *src, int src_width,
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int src_start, int src_incr, INT16 *filters)
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while (dst_width >= 4) {
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packuswb_r2r(mm7, mm0);
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packuswb_r2r(mm7, mm1);
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packuswb_r2r(mm7, mm3);
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packuswb_r2r(mm7, mm2);
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while (dst_width > 0) {
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packuswb_r2r(mm7, mm0);
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static void v_resample4_mmx(UINT8 *dst, int dst_width, UINT8 *src, int wrap,
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while (dst_width >= 4) {
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movq_m2r(s[0 * wrap], mm0);
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punpcklbw_r2r(mm7, mm0);
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movq_m2r(s[1 * wrap], mm1);
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punpcklbw_r2r(mm7, mm1);
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movq_m2r(s[2 * wrap], mm2);
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punpcklbw_r2r(mm7, mm2);
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movq_m2r(s[3 * wrap], mm3);
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punpcklbw_r2r(mm7, mm3);
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pmullw_m2r(coefs[0], mm0);
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pmullw_m2r(coefs[1], mm1);
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pmullw_m2r(coefs[2], mm2);
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pmullw_m2r(coefs[3], mm3);
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psraw_i2r(FILTER_BITS, mm0);
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packuswb_r2r(mm7, mm0);
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*(UINT32 *)dst = tmp.ud[0];
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while (dst_width > 0) {
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sum = s[0 * wrap] * filter[0] +
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s[1 * wrap] * filter[1] +
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s[2 * wrap] * filter[2] +
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s[3 * wrap] * filter[3];
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sum = sum >> FILTER_BITS;
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/* slow version to handle limit cases. Does not need optimisation */
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static void h_resample_slow(UINT8 *dst, int dst_width, UINT8 *src, int src_width,
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int src_start, int src_incr, INT16 *filters)
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int src_pos, phase, sum, j, v, i;
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src_end = src + src_width;
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for(i=0;i<dst_width;i++) {
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s = src + (src_pos >> POS_FRAC_BITS);
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phase = get_phase(src_pos);
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filter = filters + phase * NB_TAPS;
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for(j=0;j<NB_TAPS;j++) {
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else if (s >= src_end)
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sum += v * filter[j];
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sum = sum >> FILTER_BITS;
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static void h_resample(UINT8 *dst, int dst_width, UINT8 *src, int src_width,
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int src_start, int src_incr, INT16 *filters)
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n = (0 - src_start + src_incr - 1) / src_incr;
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h_resample_slow(dst, n, src, src_width, src_start, src_incr, filters);
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src_start += n * src_incr;
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src_end = src_start + dst_width * src_incr;
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if (src_end > ((src_width - NB_TAPS) << POS_FRAC_BITS)) {
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n = (((src_width - NB_TAPS + 1) << POS_FRAC_BITS) - 1 - src_start) /
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if ((mm_flags & MM_MMX) && NB_TAPS == 4)
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h_resample_fast4_mmx(dst, n,
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src, src_width, src_start, src_incr, filters);
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h_resample_fast(dst, n,
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src, src_width, src_start, src_incr, filters);
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src_start += n * src_incr;
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h_resample_slow(dst, dst_width,
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src, src_width, src_start, src_incr, filters);
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static void component_resample(ImgReSampleContext *s,
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UINT8 *output, int owrap, int owidth, int oheight,
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UINT8 *input, int iwrap, int iwidth, int iheight)
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int src_y, src_y1, last_src_y, ring_y, phase_y, y1, y;
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UINT8 *new_line, *src_line;
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last_src_y = - FCENTER - 1;
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/* position of the bottom of the filter in the source image */
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src_y = (last_src_y + NB_TAPS) * POS_FRAC;
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ring_y = NB_TAPS; /* position in ring buffer */
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for(y=0;y<oheight;y++) {
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/* apply horizontal filter on new lines from input if needed */
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src_y1 = src_y >> POS_FRAC_BITS;
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while (last_src_y < src_y1) {
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if (++ring_y >= LINE_BUF_HEIGHT + NB_TAPS)
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/* handle limit conditions : replicate line (slighly
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inefficient because we filter multiple times */
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} else if (y1 >= iheight) {
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src_line = input + y1 * iwrap;
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new_line = s->line_buf + ring_y * owidth;
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/* apply filter and handle limit cases correctly */
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h_resample(new_line, owidth,
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src_line, iwidth, - FCENTER * POS_FRAC, s->h_incr,
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&s->h_filters[0][0]);
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/* handle ring buffer wraping */
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if (ring_y >= LINE_BUF_HEIGHT) {
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memcpy(s->line_buf + (ring_y - LINE_BUF_HEIGHT) * owidth,
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/* apply vertical filter */
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phase_y = get_phase(src_y);
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/* desactivated MMX because loss of precision */
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if ((mm_flags & MM_MMX) && NB_TAPS == 4 && 0)
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v_resample4_mmx(output, owidth,
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s->line_buf + (ring_y - NB_TAPS + 1) * owidth, owidth,
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&s->v_filters[phase_y][0]);
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v_resample(output, owidth,
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s->line_buf + (ring_y - NB_TAPS + 1) * owidth, owidth,
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&s->v_filters[phase_y][0]);
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/* XXX: the following filter is quite naive, but it seems to suffice
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static void build_filter(INT16 *filter, float factor)
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float x, y, tab[NB_TAPS], norm, mult;
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/* if upsampling, only need to interpolate, no filter */
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for(ph=0;ph<NB_PHASES;ph++) {
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for(i=0;i<NB_TAPS;i++) {
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x = M_PI * ((float)(i - FCENTER) - (float)ph / NB_PHASES) * factor;
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/* normalize so that an uniform color remains the same */
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mult = (float)(1 << FILTER_BITS) / norm;
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for(i=0;i<NB_TAPS;i++) {
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v = (int)(tab[i] * mult);
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filter[ph * NB_TAPS + i] = v;
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ImgReSampleContext *img_resample_init(int owidth, int oheight,
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int iwidth, int iheight)
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ImgReSampleContext *s;
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s = av_mallocz(sizeof(ImgReSampleContext));
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s->line_buf = av_mallocz(owidth * (LINE_BUF_HEIGHT + NB_TAPS));
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s->oheight = oheight;
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s->iheight = iheight;
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s->h_incr = (iwidth * POS_FRAC) / owidth;
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s->v_incr = (iheight * POS_FRAC) / oheight;
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build_filter(&s->h_filters[0][0], (float)owidth / (float)iwidth);
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build_filter(&s->v_filters[0][0], (float)oheight / (float)iheight);
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void img_resample(ImgReSampleContext *s,
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AVPicture *output, AVPicture *input)
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shift = (i == 0) ? 0 : 1;
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component_resample(s, output->data[i], output->linesize[i],
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s->owidth >> shift, s->oheight >> shift,
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input->data[i], input->linesize[i],
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s->iwidth >> shift, s->iheight >> shift);
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void img_resample_close(ImgReSampleContext *s)
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void *av_mallocz(int size)
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memset(ptr, 0, size);
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UINT8 img[XSIZE * YSIZE];
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UINT8 img1[XSIZE1 * YSIZE1];
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UINT8 img2[XSIZE1 * YSIZE1];
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void save_pgm(const char *filename, UINT8 *img, int xsize, int ysize)
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f=fopen(filename,"w");
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fprintf(f,"P5\n%d %d\n%d\n", xsize, ysize, 255);
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fwrite(img,1, xsize * ysize,f);
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static void dump_filter(INT16 *filter)
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for(ph=0;ph<NB_PHASES;ph++) {
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for(i=0;i<NB_TAPS;i++) {
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printf(" %5.2f", filter[ph * NB_TAPS + i] / 256.0);
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int main(int argc, char **argv)
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int x, y, v, i, xsize, ysize;
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ImgReSampleContext *s;
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float fact, factors[] = { 1/2.0, 3.0/4.0, 1.0, 4.0/3.0, 16.0/9.0, 2.0 };
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/* build test image */
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for(y=0;y<YSIZE;y++) {
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for(x=0;x<XSIZE;x++) {
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if (x < XSIZE/2 && y < YSIZE/2) {
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if (x < XSIZE/4 && y < YSIZE/4) {
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} else if (x < XSIZE/4) {
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} else if (y < XSIZE/4) {
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if (((x+3) % 4) <= 1 &&
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} else if (x < XSIZE/2) {
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v = ((x - (XSIZE/2)) * 255) / (XSIZE/2);
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} else if (y < XSIZE/2) {
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v = ((y - (XSIZE/2)) * 255) / (XSIZE/2);
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v = ((x + y - XSIZE) * 255) / XSIZE;
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img[y * XSIZE + x] = v;
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save_pgm("/tmp/in.pgm", img, XSIZE, YSIZE);
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for(i=0;i<sizeof(factors)/sizeof(float);i++) {
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xsize = (int)(XSIZE * fact);
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ysize = (int)(YSIZE * fact);
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s = img_resample_init(xsize, ysize, XSIZE, YSIZE);
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printf("Factor=%0.2f\n", fact);
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dump_filter(&s->h_filters[0][0]);
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component_resample(s, img1, xsize, xsize, ysize,
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img, XSIZE, XSIZE, YSIZE);
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img_resample_close(s);
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sprintf(buf, "/tmp/out%d.pgm", i);
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save_pgm(buf, img1, xsize, ysize);
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printf("MMX test\n");
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xsize = (int)(XSIZE * fact);
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ysize = (int)(YSIZE * fact);
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s = img_resample_init(xsize, ysize, XSIZE, YSIZE);
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component_resample(s, img1, xsize, xsize, ysize,
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img, XSIZE, XSIZE, YSIZE);
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s = img_resample_init(xsize, ysize, XSIZE, YSIZE);
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component_resample(s, img2, xsize, xsize, ysize,
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img, XSIZE, XSIZE, YSIZE);
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if (memcmp(img1, img2, xsize * ysize) != 0) {
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fprintf(stderr, "mmx error\n");