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 #ifndef WEBP_UTILS_RESCALER_H_
15 #define WEBP_UTILS_RESCALER_H_
16
17 #ifdef __cplusplus
18 extern "C" {
19 #endif
20
21 #include "webp/types.h"
22
23 // Structure used for on-the-fly rescaling
24 typedef struct {
25 int x_expand; // true if we're expanding in the x direction
26 int num_channels; // bytes to jump between pixels
27 int fy_scale, fx_scale; // fixed-point scaling factor
28 int64_t fxy_scale; // ''
29 // we need hpel-precise add/sub increments, for the downsampled U/V planes.
30 int y_accum; // vertical accumulator
31 int y_add, y_sub; // vertical increments (add ~= src, sub ~= dst)
32 int x_add, x_sub; // horizontal increments (add ~= src, sub ~= dst)
33 int src_width, src_height; // source dimensions
34 int dst_width, dst_height; // destination dimensions
35 uint8_t* dst;
36 int dst_stride;
37 int32_t* irow, *frow; // work buffer
38 } WebPRescaler;
39
40 // Initialize a rescaler given scratch area 'work' and dimensions of src & dst.
41 void WebPRescalerInit(WebPRescaler* const rescaler,
42 int src_width, int src_height,
43 uint8_t* const dst,
44 int dst_width, int dst_height, int dst_stride,
45 int num_channels,
46 int x_add, int x_sub,
47 int y_add, int y_sub,
48 int32_t* const work);
49
50 // Returns the number of input lines needed next to produce one output line,
51 // considering that the maximum available input lines are 'max_num_lines'.
52 int WebPRescaleNeededLines(const WebPRescaler* const rescaler,
53 int max_num_lines);
54
55 // Import multiple rows over all channels, until at least one row is ready to
56 // be exported. Returns the actual number of lines that were imported.
57 int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows,
58 const uint8_t* src, int src_stride);
59
60 // Import a row of data and save its contribution in the rescaler.
61 // 'channel' denotes the channel number to be imported.
62 extern void (*WebPRescalerImportRow)(WebPRescaler* const wrk,
63 const uint8_t* const src, int channel);
64 // Export one row (starting at x_out position) from rescaler.
65 extern void (*WebPRescalerExportRow)(WebPRescaler* const wrk, int x_out);
66
67 // Return true if there is pending output rows ready.
68 static WEBP_INLINE
WebPRescalerHasPendingOutput(const WebPRescaler * const rescaler)69 int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) {
70 return (rescaler->y_accum <= 0);
71 }
72
73 // Export as many rows as possible. Return the numbers of rows written.
74 int WebPRescalerExport(WebPRescaler* const rescaler);
75
76 //------------------------------------------------------------------------------
77
78 #ifdef __cplusplus
79 } // extern "C"
80 #endif
81
82 #endif /* WEBP_UTILS_RESCALER_H_ */
83