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 #if defined(__cplusplus) || defined(c_plusplus)
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 wrk, int src_width, int src_height,
42 uint8_t* const dst,
43 int dst_width, int dst_height, int dst_stride,
44 int num_channels,
45 int x_add, int x_sub,
46 int y_add, int y_sub,
47 int32_t* const work);
48
49 // Import a row of data and save its contribution in the rescaler.
50 // 'channel' denotes the channel number to be imported.
51 void WebPRescalerImportRow(WebPRescaler* const rescaler,
52 const uint8_t* const src, int channel);
53
54 // Import multiple rows over all channels, until at least one row is ready to
55 // be exported. Returns the actual number of lines that were imported.
56 int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows,
57 const uint8_t* src, int src_stride);
58
59 // Return true if there is pending output rows ready.
60 static WEBP_INLINE
WebPRescalerHasPendingOutput(const WebPRescaler * const rescaler)61 int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) {
62 return (rescaler->y_accum <= 0);
63 }
64
65 // Export one row from rescaler. Returns the pointer where output was written,
66 // or NULL if no row was pending.
67 uint8_t* WebPRescalerExportRow(WebPRescaler* const wrk);
68
69 // Export as many rows as possible. Return the numbers of rows written.
70 int WebPRescalerExport(WebPRescaler* const wrk);
71
72 //------------------------------------------------------------------------------
73
74 #if defined(__cplusplus) || defined(c_plusplus)
75 } // extern "C"
76 #endif
77
78 #endif /* WEBP_UTILS_RESCALER_H_ */
79