1// Copyright 2012 Google Inc. All Rights Reserved.
2//
3// This code is licensed under the same terms as WebM:
4//  Software License Agreement:  http://www.webmproject.org/license/software/
5//  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
6// -----------------------------------------------------------------------------
7//
8// Rescaling functions
9//
10// Author: Skal (pascal.massimino@gmail.com)
11
12#include <assert.h>
13#include <stdlib.h>
14#include "./rescaler.h"
15
16//------------------------------------------------------------------------------
17
18#if defined(__cplusplus) || defined(c_plusplus)
19extern "C" {
20#endif
21
22#define RFIX 30
23#define MULT_FIX(x,y) (((int64_t)(x) * (y) + (1 << (RFIX - 1))) >> RFIX)
24
25void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height,
26                      uint8_t* const dst, int dst_width, int dst_height,
27                      int dst_stride, int num_channels, int x_add, int x_sub,
28                      int y_add, int y_sub, int32_t* const work) {
29  wrk->x_expand = (src_width < dst_width);
30  wrk->src_width = src_width;
31  wrk->src_height = src_height;
32  wrk->dst_width = dst_width;
33  wrk->dst_height = dst_height;
34  wrk->dst = dst;
35  wrk->dst_stride = dst_stride;
36  wrk->num_channels = num_channels;
37  // for 'x_expand', we use bilinear interpolation
38  wrk->x_add = wrk->x_expand ? (x_sub - 1) : x_add - x_sub;
39  wrk->x_sub = wrk->x_expand ? (x_add - 1) : x_sub;
40  wrk->y_accum = y_add;
41  wrk->y_add = y_add;
42  wrk->y_sub = y_sub;
43  wrk->fx_scale = (1 << RFIX) / x_sub;
44  wrk->fy_scale = (1 << RFIX) / y_sub;
45  wrk->fxy_scale = wrk->x_expand ?
46      ((int64_t)dst_height << RFIX) / (x_sub * src_height) :
47      ((int64_t)dst_height << RFIX) / (x_add * src_height);
48  wrk->irow = work;
49  wrk->frow = work + num_channels * dst_width;
50}
51
52void WebPRescalerImportRow(WebPRescaler* const wrk,
53                           const uint8_t* const src, int channel) {
54  const int x_stride = wrk->num_channels;
55  const int x_out_max = wrk->dst_width * wrk->num_channels;
56  int x_in = channel;
57  int x_out;
58  int accum = 0;
59  if (!wrk->x_expand) {
60    int sum = 0;
61    for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
62      accum += wrk->x_add;
63      for (; accum > 0; accum -= wrk->x_sub) {
64        sum += src[x_in];
65        x_in += x_stride;
66      }
67      {        // Emit next horizontal pixel.
68        const int32_t base = src[x_in];
69        const int32_t frac = base * (-accum);
70        x_in += x_stride;
71        wrk->frow[x_out] = (sum + base) * wrk->x_sub - frac;
72        // fresh fractional start for next pixel
73        sum = (int)MULT_FIX(frac, wrk->fx_scale);
74      }
75    }
76  } else {        // simple bilinear interpolation
77    int left = src[channel], right = src[channel];
78    for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
79      if (accum < 0) {
80        left = right;
81        x_in += x_stride;
82        right = src[x_in];
83        accum += wrk->x_add;
84      }
85      wrk->frow[x_out] = right * wrk->x_add + (left - right) * accum;
86      accum -= wrk->x_sub;
87    }
88  }
89  // Accumulate the new row's contribution
90  for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
91    wrk->irow[x_out] += wrk->frow[x_out];
92  }
93}
94
95uint8_t* WebPRescalerExportRow(WebPRescaler* const wrk) {
96  if (wrk->y_accum <= 0) {
97    int x_out;
98    uint8_t* const dst = wrk->dst;
99    int32_t* const irow = wrk->irow;
100    const int32_t* const frow = wrk->frow;
101    const int yscale = wrk->fy_scale * (-wrk->y_accum);
102    const int x_out_max = wrk->dst_width * wrk->num_channels;
103
104    for (x_out = 0; x_out < x_out_max; ++x_out) {
105      const int frac = (int)MULT_FIX(frow[x_out], yscale);
106      const int v = (int)MULT_FIX(irow[x_out] - frac, wrk->fxy_scale);
107      dst[x_out] = (!(v & ~0xff)) ? v : (v < 0) ? 0 : 255;
108      irow[x_out] = frac;   // new fractional start
109    }
110    wrk->y_accum += wrk->y_add;
111    wrk->dst += wrk->dst_stride;
112    return dst;
113  } else {
114    return NULL;
115  }
116}
117
118#undef MULT_FIX
119#undef RFIX
120
121//------------------------------------------------------------------------------
122// all-in-one calls
123
124int WebPRescalerImport(WebPRescaler* const wrk, int num_lines,
125                       const uint8_t* src, int src_stride) {
126  int total_imported = 0;
127  while (total_imported < num_lines && wrk->y_accum > 0) {
128    int channel;
129    for (channel = 0; channel < wrk->num_channels; ++channel) {
130      WebPRescalerImportRow(wrk, src, channel);
131    }
132    src += src_stride;
133    ++total_imported;
134    wrk->y_accum -= wrk->y_sub;
135  }
136  return total_imported;
137}
138
139int WebPRescalerExport(WebPRescaler* const rescaler) {
140  int total_exported = 0;
141  while (WebPRescalerHasPendingOutput(rescaler)) {
142    WebPRescalerExportRow(rescaler);
143    ++total_exported;
144  }
145  return total_exported;
146}
147
148//------------------------------------------------------------------------------
149
150#if defined(__cplusplus) || defined(c_plusplus)
151}    // extern "C"
152#endif
153