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_UTILS_H_ |
15 | #define WEBP_UTILS_RESCALER_UTILS_H_ |
16 | |
17 | #ifdef __cplusplus |
18 | extern "C" { |
19 | #endif |
20 | |
21 | #include "src/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 |
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 |
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 |
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_UTILS_H_ |
102 | |