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 */