1 // Copyright 2012 Google Inc. All Rights Reserved.
2 //
3 // Use of this source code is governed by a BSD-style license
4 // that can be found in the COPYING file in the root of the source
5 // tree. An additional intellectual property rights grant can be found
6 // in the file PATENTS. All contributing project authors may
7 // be found in the AUTHORS file in the root of the source tree.
8 // -----------------------------------------------------------------------------
9 //
10 // Rescaling functions
11 //
12 // Author: Skal (pascal.massimino@gmail.com)
13
14 #include <assert.h>
15 #include <stdlib.h>
16 #include <string.h>
17 #include "src/dsp/dsp.h"
18 #include "src/utils/rescaler_utils.h"
19
20 //------------------------------------------------------------------------------
21
WebPRescalerInit(WebPRescaler * const wrk,int src_width,int src_height,uint8_t * const dst,int dst_width,int dst_height,int dst_stride,int num_channels,rescaler_t * const work)22 void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height,
23 uint8_t* const dst,
24 int dst_width, int dst_height, int dst_stride,
25 int num_channels, rescaler_t* const work) {
26 const int x_add = src_width, x_sub = dst_width;
27 const int y_add = src_height, y_sub = dst_height;
28 wrk->x_expand = (src_width < dst_width);
29 wrk->y_expand = (src_height < dst_height);
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->src_y = 0;
35 wrk->dst_y = 0;
36 wrk->dst = dst;
37 wrk->dst_stride = dst_stride;
38 wrk->num_channels = num_channels;
39
40 // for 'x_expand', we use bilinear interpolation
41 wrk->x_add = wrk->x_expand ? (x_sub - 1) : x_add;
42 wrk->x_sub = wrk->x_expand ? (x_add - 1) : x_sub;
43 if (!wrk->x_expand) { // fx_scale is not used otherwise
44 wrk->fx_scale = WEBP_RESCALER_FRAC(1, wrk->x_sub);
45 }
46 // vertical scaling parameters
47 wrk->y_add = wrk->y_expand ? y_add - 1 : y_add;
48 wrk->y_sub = wrk->y_expand ? y_sub - 1 : y_sub;
49 wrk->y_accum = wrk->y_expand ? wrk->y_sub : wrk->y_add;
50 if (!wrk->y_expand) {
51 // This is WEBP_RESCALER_FRAC(dst_height, x_add * y_add) without the cast.
52 // Its value is <= WEBP_RESCALER_ONE, because dst_height <= wrk->y_add, and
53 // wrk->x_add >= 1;
54 const uint64_t ratio =
55 (uint64_t)dst_height * WEBP_RESCALER_ONE / (wrk->x_add * wrk->y_add);
56 if (ratio != (uint32_t)ratio) {
57 // When ratio == WEBP_RESCALER_ONE, we can't represent the ratio with the
58 // current fixed-point precision. This happens when src_height ==
59 // wrk->y_add (which == src_height), and wrk->x_add == 1.
60 // => We special-case fxy_scale = 0, in WebPRescalerExportRow().
61 wrk->fxy_scale = 0;
62 } else {
63 wrk->fxy_scale = (uint32_t)ratio;
64 }
65 wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->y_sub);
66 } else {
67 wrk->fy_scale = WEBP_RESCALER_FRAC(1, wrk->x_add);
68 // wrk->fxy_scale is unused here.
69 }
70 wrk->irow = work;
71 wrk->frow = work + num_channels * dst_width;
72 memset(work, 0, 2 * dst_width * num_channels * sizeof(*work));
73
74 WebPRescalerDspInit();
75 }
76
WebPRescalerGetScaledDimensions(int src_width,int src_height,int * const scaled_width,int * const scaled_height)77 int WebPRescalerGetScaledDimensions(int src_width, int src_height,
78 int* const scaled_width,
79 int* const scaled_height) {
80 assert(scaled_width != NULL);
81 assert(scaled_height != NULL);
82 {
83 int width = *scaled_width;
84 int height = *scaled_height;
85
86 // if width is unspecified, scale original proportionally to height ratio.
87 if (width == 0 && src_height > 0) {
88 width =
89 (int)(((uint64_t)src_width * height + src_height - 1) / src_height);
90 }
91 // if height is unspecified, scale original proportionally to width ratio.
92 if (height == 0 && src_width > 0) {
93 height =
94 (int)(((uint64_t)src_height * width + src_width - 1) / src_width);
95 }
96 // Check if the overall dimensions still make sense.
97 if (width <= 0 || height <= 0) {
98 return 0;
99 }
100
101 *scaled_width = width;
102 *scaled_height = height;
103 return 1;
104 }
105 }
106
107 //------------------------------------------------------------------------------
108 // all-in-one calls
109
WebPRescaleNeededLines(const WebPRescaler * const wrk,int max_num_lines)110 int WebPRescaleNeededLines(const WebPRescaler* const wrk, int max_num_lines) {
111 const int num_lines = (wrk->y_accum + wrk->y_sub - 1) / wrk->y_sub;
112 return (num_lines > max_num_lines) ? max_num_lines : num_lines;
113 }
114
WebPRescalerImport(WebPRescaler * const wrk,int num_lines,const uint8_t * src,int src_stride)115 int WebPRescalerImport(WebPRescaler* const wrk, int num_lines,
116 const uint8_t* src, int src_stride) {
117 int total_imported = 0;
118 while (total_imported < num_lines && !WebPRescalerHasPendingOutput(wrk)) {
119 if (wrk->y_expand) {
120 rescaler_t* const tmp = wrk->irow;
121 wrk->irow = wrk->frow;
122 wrk->frow = tmp;
123 }
124 WebPRescalerImportRow(wrk, src);
125 if (!wrk->y_expand) { // Accumulate the contribution of the new row.
126 int x;
127 for (x = 0; x < wrk->num_channels * wrk->dst_width; ++x) {
128 wrk->irow[x] += wrk->frow[x];
129 }
130 }
131 ++wrk->src_y;
132 src += src_stride;
133 ++total_imported;
134 wrk->y_accum -= wrk->y_sub;
135 }
136 return total_imported;
137 }
138
WebPRescalerExport(WebPRescaler * const rescaler)139 int 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