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 #define WEBP_RESCALER_RFIX 32 // fixed-point precision for multiplies
24 #define WEBP_RESCALER_ONE (1ull << WEBP_RESCALER_RFIX)
25 #define WEBP_RESCALER_FRAC(x, y) \
26 ((uint32_t)(((uint64_t)(x) << WEBP_RESCALER_RFIX) / (y)))
27
28 // Structure used for on-the-fly rescaling
29 typedef uint32_t rescaler_t; // type for side-buffer
30 typedef struct WebPRescaler WebPRescaler;
31 struct WebPRescaler {
32 int x_expand; // true if we're expanding in the x direction
33 int y_expand; // true if we're expanding in the y direction
34 int num_channels; // bytes to jump between pixels
35 uint32_t fx_scale; // fixed-point scaling factors
36 uint32_t fy_scale; // ''
37 uint32_t fxy_scale; // ''
38 int y_accum; // vertical accumulator
39 int y_add, y_sub; // vertical increments
40 int x_add, x_sub; // horizontal increments
41 int src_width, src_height; // source dimensions
42 int dst_width, dst_height; // destination dimensions
43 int src_y, dst_y; // row counters for input and output
44 uint8_t* dst;
45 int dst_stride;
46 rescaler_t* irow, *frow; // work buffer
47 };
48
49 // Initialize a rescaler given scratch area 'work' and dimensions of src & dst.
50 void WebPRescalerInit(WebPRescaler* const rescaler,
51 int src_width, int src_height,
52 uint8_t* const dst,
53 int dst_width, int dst_height, int dst_stride,
54 int num_channels,
55 rescaler_t* const work);
56
57 // If either 'scaled_width' or 'scaled_height' (but not both) is 0 the value
58 // will be calculated preserving the aspect ratio, otherwise the values are
59 // left unmodified. Returns true on success, false if either value is 0 after
60 // performing the scaling calculation.
61 int WebPRescalerGetScaledDimensions(int src_width, int src_height,
62 int* const scaled_width,
63 int* const scaled_height);
64
65 // Returns the number of input lines needed next to produce one output line,
66 // considering that the maximum available input lines are 'max_num_lines'.
67 int WebPRescaleNeededLines(const WebPRescaler* const rescaler,
68 int max_num_lines);
69
70 // Import multiple rows over all channels, until at least one row is ready to
71 // be exported. Returns the actual number of lines that were imported.
72 int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows,
73 const uint8_t* src, int src_stride);
74
75 // Export as many rows as possible. Return the numbers of rows written.
76 int WebPRescalerExport(WebPRescaler* const rescaler);
77
78 // Return true if input is finished
79 static WEBP_INLINE
WebPRescalerInputDone(const WebPRescaler * const rescaler)80 int WebPRescalerInputDone(const WebPRescaler* const rescaler) {
81 return (rescaler->src_y >= rescaler->src_height);
82 }
83 // Return true if output is finished
84 static WEBP_INLINE
WebPRescalerOutputDone(const WebPRescaler * const rescaler)85 int WebPRescalerOutputDone(const WebPRescaler* const rescaler) {
86 return (rescaler->dst_y >= rescaler->dst_height);
87 }
88
89 // Return true if there are pending output rows ready.
90 static WEBP_INLINE
WebPRescalerHasPendingOutput(const WebPRescaler * const rescaler)91 int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) {
92 return !WebPRescalerOutputDone(rescaler) && (rescaler->y_accum <= 0);
93 }
94
95 //------------------------------------------------------------------------------
96
97 #ifdef __cplusplus
98 } // extern "C"
99 #endif
100
101 #endif /* WEBP_UTILS_RESCALER_H_ */
102