Fix grammar: write to DST THING -> write THING to DST.
[libav.git] / libavutil / pixdesc.h
1 /*
2 * pixel format descriptor
3 * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 #ifndef AVUTIL_PIXDESC_H
23 #define AVUTIL_PIXDESC_H
24
25 #include <inttypes.h>
26
27 #include "intreadwrite.h"
28
29 typedef struct AVComponentDescriptor{
30 uint16_t plane :2; ///< which of the 4 planes contains the component
31
32 /**
33 * Number of elements between 2 horizontally consecutive pixels minus 1.
34 * Elements are bits for bitstream formats, bytes otherwise.
35 */
36 uint16_t step_minus1 :3;
37
38 /**
39 * Number of elements before the component of the first pixel plus 1.
40 * Elements are bits for bitstream formats, bytes otherwise.
41 */
42 uint16_t offset_plus1 :3;
43 uint16_t shift :3; ///< number of least significant bits that must be shifted away to get the value
44 uint16_t depth_minus1 :4; ///< number of bits in the component minus 1
45 }AVComponentDescriptor;
46
47 /**
48 * Descriptor that unambiguously describes how the bits of a pixel are
49 * stored in the up to 4 data planes of an image. It also stores the
50 * subsampling factors and number of components.
51 *
52 * @note This is separate of the colorspace (RGB, YCbCr, YPbPr, JPEG-style YUV
53 * and all the YUV variants) AVPixFmtDescriptor just stores how values
54 * are stored not what these values represent.
55 */
56 typedef struct AVPixFmtDescriptor{
57 const char *name;
58 uint8_t nb_components; ///< The number of components each pixel has, (1-4)
59
60 /**
61 * Amount to shift the luma width right to find the chroma width.
62 * For YV12 this is 1 for example.
63 * chroma_width = -((-luma_width) >> log2_chroma_w)
64 * The note above is needed to ensure rounding up.
65 * This value only refers to the chroma components.
66 */
67 uint8_t log2_chroma_w; ///< chroma_width = -((-luma_width )>>log2_chroma_w)
68
69 /**
70 * Amount to shift the luma height right to find the chroma height.
71 * For YV12 this is 1 for example.
72 * chroma_height= -((-luma_height) >> log2_chroma_h)
73 * The note above is needed to ensure rounding up.
74 * This value only refers to the chroma components.
75 */
76 uint8_t log2_chroma_h;
77 uint8_t flags;
78
79 /**
80 * Parameters that describe how pixels are packed. If the format
81 * has chroma components, they must be stored in comp[1] and
82 * comp[2].
83 */
84 AVComponentDescriptor comp[4];
85 }AVPixFmtDescriptor;
86
87 #define PIX_FMT_BE 1 ///< Pixel format is big-endian.
88 #define PIX_FMT_PAL 2 ///< Pixel format has a palette in data[1], values are indexes in this palette.
89 #define PIX_FMT_BITSTREAM 4 ///< All values of a component are bit-wise packed end to end.
90 #define PIX_FMT_HWACCEL 8 ///< Pixel format is an HW accelerated format.
91
92 /**
93 * The array of all the pixel format descriptors.
94 */
95 extern const AVPixFmtDescriptor av_pix_fmt_descriptors[];
96
97 /**
98 * Reads a line from an image, and writes the values of the
99 * pixel format component c to dst.
100 *
101 * @param data the array containing the pointers to the planes of the image
102 * @param linesizes the array containing the linesizes of the image
103 * @param desc the pixel format descriptor for the image
104 * @param x the horizontal coordinate of the first pixel to read
105 * @param y the vertical coordinate of the first pixel to read
106 * @param w the width of the line to read, that is the number of
107 * values to write to dst
108 * @param read_pal_component if not zero and the format is a paletted
109 * format writes the values corresponding to the palette
110 * component c in data[1] to dst, rather than the palette indexes in
111 * data[0]. The behavior is undefined if the format is not paletted.
112 */
113 static inline void read_line(uint16_t *dst, const uint8_t *data[4], const int linesize[4],
114 const AVPixFmtDescriptor *desc, int x, int y, int c, int w, int read_pal_component)
115 {
116 AVComponentDescriptor comp= desc->comp[c];
117 int plane= comp.plane;
118 int depth= comp.depth_minus1+1;
119 int mask = (1<<depth)-1;
120 int shift= comp.shift;
121 int step = comp.step_minus1+1;
122 int flags= desc->flags;
123
124 if (flags & PIX_FMT_BITSTREAM){
125 int skip = x*step + comp.offset_plus1-1;
126 const uint8_t *p = data[plane] + y*linesize[plane] + (skip>>3);
127 int shift = 8 - depth - (skip&7);
128
129 while(w--){
130 int val = (*p >> shift) & mask;
131 if(read_pal_component)
132 val= data[1][4*val + c];
133 shift -= step;
134 p -= shift>>3;
135 shift &= 7;
136 *dst++= val;
137 }
138 } else {
139 const uint8_t *p = data[plane]+ y*linesize[plane] + x*step + comp.offset_plus1-1;
140
141 while(w--){
142 int val;
143 if(flags & PIX_FMT_BE) val= AV_RB16(p);
144 else val= AV_RL16(p);
145 val = (val>>shift) & mask;
146 if(read_pal_component)
147 val= data[1][4*val + c];
148 p+= step;
149 *dst++= val;
150 }
151 }
152 }
153
154 /**
155 * Writes the values from src to the pixel format component c of an
156 * image line.
157 *
158 * @param src array containing the values to write
159 * @param data the array containing the pointers to the planes of the
160 * image to write into. It is supposed to be zeroed.
161 * @param linesizes the array containing the linesizes of the image
162 * @param desc the pixel format descriptor for the image
163 * @param x the horizontal coordinate of the first pixel to write
164 * @param y the vertical coordinate of the first pixel to write
165 * @param w the width of the line to write, that is the number of
166 * values to write to the image line
167 */
168 static inline void write_line(const uint16_t *src, uint8_t *data[4], const int linesize[4],
169 const AVPixFmtDescriptor *desc, int x, int y, int c, int w)
170 {
171 AVComponentDescriptor comp = desc->comp[c];
172 int plane = comp.plane;
173 int depth = comp.depth_minus1+1;
174 int step = comp.step_minus1+1;
175 int flags = desc->flags;
176
177 if (flags & PIX_FMT_BITSTREAM) {
178 int skip = x*step + comp.offset_plus1-1;
179 uint8_t *p = data[plane] + y*linesize[plane] + (skip>>3);
180 int shift = 8 - depth - (skip&7);
181
182 while (w--) {
183 *p |= *src++ << shift;
184 shift -= step;
185 p -= shift>>3;
186 shift &= 7;
187 }
188 } else {
189 int shift = comp.shift;
190 uint8_t *p = data[plane]+ y*linesize[plane] + x*step + comp.offset_plus1-1;
191
192 while (w--) {
193 if (flags & PIX_FMT_BE) {
194 uint16_t val = AV_RB16(p) | (*src++<<shift);
195 AV_WB16(p, val);
196 } else {
197 uint16_t val = AV_RL16(p) | (*src++<<shift);
198 AV_WL16(p, val);
199 }
200 p+= step;
201 }
202 }
203 }
204
205 /**
206 * Returns the pixel format corresponding to name.
207 *
208 * If there is no pixel format with name name, then looks for a
209 * pixel format with the name corresponding to the native endian
210 * format of name.
211 * For example in a little-endian system, first looks for "gray16",
212 * then for "gray16le".
213 *
214 * Finally if no pixel format has been found, returns PIX_FMT_NONE.
215 */
216 enum PixelFormat av_get_pix_fmt(const char *name);
217
218 /**
219 * Returns the number of bits per pixel used by the pixel format
220 * described by pixdesc.
221 *
222 * The returned number of bits refers to the number of bits actually
223 * used for storing the pixel information, that is padding bits are
224 * not counted.
225 */
226 int av_get_bits_per_pixel(const AVPixFmtDescriptor *pixdesc);
227
228 #endif /* AVUTIL_PIXDESC_H */