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pixdesc.h
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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 "attributes.h"
28 #include "pixfmt.h"
29 
30 typedef struct AVComponentDescriptor {
31  /**
32  * Which of the 4 planes contains the component.
33  */
34  uint16_t plane : 2;
35 
36  /**
37  * Number of elements between 2 horizontally consecutive pixels minus 1.
38  * Elements are bits for bitstream formats, bytes otherwise.
39  */
40  uint16_t step_minus1 : 3;
41 
42  /**
43  * Number of elements before the component of the first pixel plus 1.
44  * Elements are bits for bitstream formats, bytes otherwise.
45  */
46  uint16_t offset_plus1 : 3;
47 
48  /**
49  * Number of least significant bits that must be shifted away
50  * to get the value.
51  */
52  uint16_t shift : 3;
53 
54  /**
55  * Number of bits in the component minus 1.
56  */
57  uint16_t depth_minus1 : 4;
59 
60 /**
61  * Descriptor that unambiguously describes how the bits of a pixel are
62  * stored in the up to 4 data planes of an image. It also stores the
63  * subsampling factors and number of components.
64  *
65  * @note This is separate of the colorspace (RGB, YCbCr, YPbPr, JPEG-style YUV
66  * and all the YUV variants) AVPixFmtDescriptor just stores how values
67  * are stored not what these values represent.
68  */
69 typedef struct AVPixFmtDescriptor {
70  const char *name;
71  uint8_t nb_components; ///< The number of components each pixel has, (1-4)
72 
73  /**
74  * Amount to shift the luma width right to find the chroma width.
75  * For YV12 this is 1 for example.
76  * chroma_width = -((-luma_width) >> log2_chroma_w)
77  * The note above is needed to ensure rounding up.
78  * This value only refers to the chroma components.
79  */
80  uint8_t log2_chroma_w; ///< chroma_width = -((-luma_width )>>log2_chroma_w)
81 
82  /**
83  * Amount to shift the luma height right to find the chroma height.
84  * For YV12 this is 1 for example.
85  * chroma_height= -((-luma_height) >> log2_chroma_h)
86  * The note above is needed to ensure rounding up.
87  * This value only refers to the chroma components.
88  */
91 
92  /**
93  * Parameters that describe how pixels are packed.
94  * If the format has 2 or 4 components, then alpha is last.
95  * If the format has 1 or 2 components, then luma is 0.
96  * If the format has 3 or 4 components,
97  * if the RGB flag is set then 0 is red, 1 is green and 2 is blue;
98  * otherwise 0 is luma, 1 is chroma-U and 2 is chroma-V.
99  */
101 
102  /**
103  * Alternative comma-separated names.
104  */
105  const char *alias;
107 
108 /**
109  * Pixel format is big-endian.
110  */
111 #define AV_PIX_FMT_FLAG_BE (1 << 0)
112 /**
113  * Pixel format has a palette in data[1], values are indexes in this palette.
114  */
115 #define AV_PIX_FMT_FLAG_PAL (1 << 1)
116 /**
117  * All values of a component are bit-wise packed end to end.
118  */
119 #define AV_PIX_FMT_FLAG_BITSTREAM (1 << 2)
120 /**
121  * Pixel format is an HW accelerated format.
122  */
123 #define AV_PIX_FMT_FLAG_HWACCEL (1 << 3)
124 /**
125  * At least one pixel component is not in the first data plane.
126  */
127 #define AV_PIX_FMT_FLAG_PLANAR (1 << 4)
128 /**
129  * The pixel format contains RGB-like data (as opposed to YUV/grayscale).
130  */
131 #define AV_PIX_FMT_FLAG_RGB (1 << 5)
132 /**
133  * The pixel format is "pseudo-paletted". This means that FFmpeg treats it as
134  * paletted internally, but the palette is generated by the decoder and is not
135  * stored in the file.
136  */
137 #define AV_PIX_FMT_FLAG_PSEUDOPAL (1 << 6)
138 /**
139  * The pixel format has an alpha channel.
140  */
141 #define AV_PIX_FMT_FLAG_ALPHA (1 << 7)
142 
143 #if FF_API_PIX_FMT
144 /**
145  * @deprecated use the AV_PIX_FMT_FLAG_* flags
146  */
147 #define PIX_FMT_BE AV_PIX_FMT_FLAG_BE
148 #define PIX_FMT_PAL AV_PIX_FMT_FLAG_PAL
149 #define PIX_FMT_BITSTREAM AV_PIX_FMT_FLAG_BITSTREAM
150 #define PIX_FMT_HWACCEL AV_PIX_FMT_FLAG_HWACCEL
151 #define PIX_FMT_PLANAR AV_PIX_FMT_FLAG_PLANAR
152 #define PIX_FMT_RGB AV_PIX_FMT_FLAG_RGB
153 #define PIX_FMT_PSEUDOPAL AV_PIX_FMT_FLAG_PSEUDOPAL
154 #define PIX_FMT_ALPHA AV_PIX_FMT_FLAG_ALPHA
155 #endif
156 
157 #if FF_API_PIX_FMT_DESC
158 /**
159  * The array of all the pixel format descriptors.
160  */
162 #endif
163 
164 /**
165  * Read a line from an image, and write the values of the
166  * pixel format component c to dst.
167  *
168  * @param data the array containing the pointers to the planes of the image
169  * @param linesize the array containing the linesizes of the image
170  * @param desc the pixel format descriptor for the image
171  * @param x the horizontal coordinate of the first pixel to read
172  * @param y the vertical coordinate of the first pixel to read
173  * @param w the width of the line to read, that is the number of
174  * values to write to dst
175  * @param read_pal_component if not zero and the format is a paletted
176  * format writes the values corresponding to the palette
177  * component c in data[1] to dst, rather than the palette indexes in
178  * data[0]. The behavior is undefined if the format is not paletted.
179  */
180 void av_read_image_line(uint16_t *dst, const uint8_t *data[4],
181  const int linesize[4], const AVPixFmtDescriptor *desc,
182  int x, int y, int c, int w, int read_pal_component);
183 
184 /**
185  * Write the values from src to the pixel format component c of an
186  * image line.
187  *
188  * @param src array containing the values to write
189  * @param data the array containing the pointers to the planes of the
190  * image to write into. It is supposed to be zeroed.
191  * @param linesize the array containing the linesizes of the image
192  * @param desc the pixel format descriptor for the image
193  * @param x the horizontal coordinate of the first pixel to write
194  * @param y the vertical coordinate of the first pixel to write
195  * @param w the width of the line to write, that is the number of
196  * values to write to the image line
197  */
198 void av_write_image_line(const uint16_t *src, uint8_t *data[4],
199  const int linesize[4], const AVPixFmtDescriptor *desc,
200  int x, int y, int c, int w);
201 
202 /**
203  * Return the pixel format corresponding to name.
204  *
205  * If there is no pixel format with name name, then looks for a
206  * pixel format with the name corresponding to the native endian
207  * format of name.
208  * For example in a little-endian system, first looks for "gray16",
209  * then for "gray16le".
210  *
211  * Finally if no pixel format has been found, returns AV_PIX_FMT_NONE.
212  */
213 enum AVPixelFormat av_get_pix_fmt(const char *name);
214 
215 /**
216  * Return the short name for a pixel format, NULL in case pix_fmt is
217  * unknown.
218  *
219  * @see av_get_pix_fmt(), av_get_pix_fmt_string()
220  */
221 const char *av_get_pix_fmt_name(enum AVPixelFormat pix_fmt);
222 
223 /**
224  * Print in buf the string corresponding to the pixel format with
225  * number pix_fmt, or a header if pix_fmt is negative.
226  *
227  * @param buf the buffer where to write the string
228  * @param buf_size the size of buf
229  * @param pix_fmt the number of the pixel format to print the
230  * corresponding info string, or a negative value to print the
231  * corresponding header.
232  */
233 char *av_get_pix_fmt_string(char *buf, int buf_size,
234  enum AVPixelFormat pix_fmt);
235 
236 /**
237  * Return the number of bits per pixel used by the pixel format
238  * described by pixdesc. Note that this is not the same as the number
239  * of bits per sample.
240  *
241  * The returned number of bits refers to the number of bits actually
242  * used for storing the pixel information, that is padding bits are
243  * not counted.
244  */
245 int av_get_bits_per_pixel(const AVPixFmtDescriptor *pixdesc);
246 
247 /**
248  * Return the number of bits per pixel for the pixel format
249  * described by pixdesc, including any padding or unused bits.
250  */
252 
253 /**
254  * @return a pixel format descriptor for provided pixel format or NULL if
255  * this pixel format is unknown.
256  */
258 
259 /**
260  * Iterate over all pixel format descriptors known to libavutil.
261  *
262  * @param prev previous descriptor. NULL to get the first descriptor.
263  *
264  * @return next descriptor or NULL after the last descriptor
265  */
267 
268 /**
269  * @return an AVPixelFormat id described by desc, or AV_PIX_FMT_NONE if desc
270  * is not a valid pointer to a pixel format descriptor.
271  */
273 
274 /**
275  * Utility function to access log2_chroma_w log2_chroma_h from
276  * the pixel format AVPixFmtDescriptor.
277  *
278  * See av_get_chroma_sub_sample() for a function that asserts a
279  * valid pixel format instead of returning an error code.
280  * Its recommended that you use avcodec_get_chroma_sub_sample unless
281  * you do check the return code!
282  *
283  * @param[in] pix_fmt the pixel format
284  * @param[out] h_shift store log2_chroma_w
285  * @param[out] v_shift store log2_chroma_h
286  *
287  * @return 0 on success, AVERROR(ENOSYS) on invalid or unknown pixel format
288  */
290  int *h_shift, int *v_shift);
291 
292 /**
293  * @return number of planes in pix_fmt, a negative AVERROR if pix_fmt is not a
294  * valid pixel format.
295  */
297 
298 void ff_check_pixfmt_descriptors(void);
299 
300 /**
301  * Utility function to swap the endianness of a pixel format.
302  *
303  * @param[in] pix_fmt the pixel format
304  *
305  * @return pixel format with swapped endianness if it exists,
306  * otherwise AV_PIX_FMT_NONE
307  */
309 
310 #define FF_LOSS_RESOLUTION 0x0001 /**< loss due to resolution change */
311 #define FF_LOSS_DEPTH 0x0002 /**< loss due to color depth change */
312 #define FF_LOSS_COLORSPACE 0x0004 /**< loss due to color space conversion */
313 #define FF_LOSS_ALPHA 0x0008 /**< loss of alpha bits */
314 #define FF_LOSS_COLORQUANT 0x0010 /**< loss due to color quantization */
315 #define FF_LOSS_CHROMA 0x0020 /**< loss of chroma (e.g. RGB to gray conversion) */
316 
317 /**
318  * Compute what kind of losses will occur when converting from one specific
319  * pixel format to another.
320  * When converting from one pixel format to another, information loss may occur.
321  * For example, when converting from RGB24 to GRAY, the color information will
322  * be lost. Similarly, other losses occur when converting from some formats to
323  * other formats. These losses can involve loss of chroma, but also loss of
324  * resolution, loss of color depth, loss due to the color space conversion, loss
325  * of the alpha bits or loss due to color quantization.
326  * av_get_fix_fmt_loss() informs you about the various types of losses
327  * which will occur when converting from one pixel format to another.
328  *
329  * @param[in] dst_pix_fmt destination pixel format
330  * @param[in] src_pix_fmt source pixel format
331  * @param[in] has_alpha Whether the source pixel format alpha channel is used.
332  * @return Combination of flags informing you what kind of losses will occur
333  * (maximum loss for an invalid dst_pix_fmt).
334  */
335 int av_get_pix_fmt_loss(enum AVPixelFormat dst_pix_fmt,
336  enum AVPixelFormat src_pix_fmt,
337  int has_alpha);
338 
339 /**
340  * Compute what kind of losses will occur when converting from one specific
341  * pixel format to another.
342  * When converting from one pixel format to another, information loss may occur.
343  * For example, when converting from RGB24 to GRAY, the color information will
344  * be lost. Similarly, other losses occur when converting from some formats to
345  * other formats. These losses can involve loss of chroma, but also loss of
346  * resolution, loss of color depth, loss due to the color space conversion, loss
347  * of the alpha bits or loss due to color quantization.
348  * av_get_fix_fmt_loss() informs you about the various types of losses
349  * which will occur when converting from one pixel format to another.
350  *
351  * @param[in] dst_pix_fmt destination pixel format
352  * @param[in] src_pix_fmt source pixel format
353  * @param[in] has_alpha Whether the source pixel format alpha channel is used.
354  * @return Combination of flags informing you what kind of losses will occur
355  * (maximum loss for an invalid dst_pix_fmt).
356  */
357 enum AVPixelFormat av_find_best_pix_fmt_of_2(enum AVPixelFormat dst_pix_fmt1, enum AVPixelFormat dst_pix_fmt2,
358  enum AVPixelFormat src_pix_fmt, int has_alpha, int *loss_ptr);
359 #endif /* AVUTIL_PIXDESC_H */