libavcodec/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 AVCODEC_PIXDESC_H
  23 #define AVCODEC_PIXDESC_H
  24
  25 #include <inttypes.h>
  26
  27 #include "libavutil/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_channels;        ///< 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      */
  66     uint8_t log2_chroma_w;      ///< chroma_width = -((-luma_width )>>log2_chroma_w)
  67
  68     /**
  69      * Amount to shift the luma height right to find the chroma height.
  70      * For YV12 this is 1 for example.
  71      * chroma_height= -((-luma_height) >> log2_chroma_h)
  72      * The note above is needed to ensure rounding up.
  73      */
  74     uint8_t log2_chroma_h;
  75     uint8_t flags;
  76     AVComponentDescriptor comp[4]; ///< parameters that describe how pixels are packed
  77 }AVPixFmtDescriptor;
  78
  79 #define PIX_FMT_BE        1 ///< big-endian
  80 #define PIX_FMT_PAL       2 ///< Pixel format has a palette in data[1], values are indexes in this palette.
  81 #define PIX_FMT_BITSTREAM 4 ///< All values of a component are bit-wise packed end to end.
  82
  83 /**
  84  * The array of all the pixel format descriptors.
  85  */
  86 extern const AVPixFmtDescriptor av_pix_fmt_descriptors[];
  87
  88 /**
  89  * Reads a line from an image, and writes to dst the values of the
  90  * pixel format component c.
  91  *
  92  * @param data the array containing the pointers to the planes of the image
  93  * @param linesizes the array containing the linesizes of the image
  94  * @param desc the pixel format descriptor for the image
  95  * @param x the horizontal coordinate of the first pixel to read
  96  * @param y the vertical coordinate of the first pixel to read
  97  * @param w the width of the line to read, that is the number of
  98  * values to write to dst
  99  * @param read_pal_component if not zero and the format is a paletted
 100  * format writes to dst the values corresponding to the palette
 101  * component c in data[1], rather than the palette indexes in
 102  * data[0]. The behavior is undefined if the format is not paletted.
 103  */
 104 static inline void read_line(uint16_t *dst, const uint8_t *data[4], const int linesize[4],
 105                              const AVPixFmtDescriptor *desc, int x, int y, int c, int w, int read_pal_component)
 106 {
 107     AVComponentDescriptor comp= desc->comp[c];
 108     int plane= comp.plane;
 109     int depth= comp.depth_minus1+1;
 110     int mask = (1<<depth)-1;
 111     int shift= comp.shift;
 112     int step = comp.step_minus1+1;
 113     int flags= desc->flags;
 114
 115     if (flags & PIX_FMT_BITSTREAM){
 116         int skip = x*step + comp.offset_plus1-1;
 117         const uint8_t *p = data[plane] + y*linesize[plane] + (skip>>3);
 118         int shift = 8 - depth - (skip&7);
 119
 120         while(w--){
 121             int val = (*p >> shift) & mask;
 122             if(read_pal_component)
 123                 val= data[1][4*val + c];
 124             shift -= step;
 125             p -= shift>>3;
 126             shift &= 7;
 127             *dst++= val;
 128         }
 129     } else {
 130         const uint8_t *p = data[plane]+ y*linesize[plane] + x*step + comp.offset_plus1-1;
 131
 132         while(w--){
 133             int val;
 134             if(flags & PIX_FMT_BE) val= AV_RB16(p);
 135             else                   val= AV_RL16(p);
 136             val = (val>>shift) & mask;
 137             if(read_pal_component)
 138                 val= data[1][4*val + c];
 139             p+= step;
 140             *dst++= val;
 141         }
 142     }
 143 }
 144
 145 /**
 146  * Writes the values from src to the pixel format component c of an
 147  * image line.
 148  *
 149  * @param src array containing the values to write
 150  * @param data the array containing the pointers to the planes of the
 151  * image to write into. It is supposed to be zeroed.
 152  * @param linesizes the array containing the linesizes of the image
 153  * @param desc the pixel format descriptor for the image
 154  * @param x the horizontal coordinate of the first pixel to write
 155  * @param y the vertical coordinate of the first pixel to write
 156  * @param w the width of the line to write, that is the number of
 157  * values to write to the image line
 158  */
 159 static inline void write_line(const uint16_t *src, uint8_t *data[4], const int linesize[4],
 160                               const AVPixFmtDescriptor *desc, int x, int y, int c, int w)
 161 {
 162     AVComponentDescriptor comp = desc->comp[c];
 163     int plane = comp.plane;
 164     int depth = comp.depth_minus1+1;
 165     int step  = comp.step_minus1+1;
 166     int flags = desc->flags;
 167
 168     if (flags & PIX_FMT_BITSTREAM) {
 169         int skip = x*step + comp.offset_plus1-1;
 170         uint8_t *p = data[plane] + y*linesize[plane] + (skip>>3);
 171         int shift = 8 - depth - (skip&7);
 172
 173         while (w--) {
 174             *p |= *src++ << shift;
 175             shift -= step;
 176             p -= shift>>3;
 177             shift &= 7;
 178         }
 179     } else {
 180         int shift = comp.shift;
 181         uint8_t *p = data[plane]+ y*linesize[plane] + x*step + comp.offset_plus1-1;
 182
 183         while (w--) {
 184             if (flags & PIX_FMT_BE) {
 185                 uint16_t val = AV_RB16(p) | (*src++<<shift);
 186                 AV_WB16(p, val);
 187             } else {
 188                 uint16_t val = AV_RL16(p) | (*src++<<shift);
 189                 AV_WL16(p, val);
 190             }
 191             p+= step;
 192         }
 193     }
 194 }
 195
 196 /**
 197  * Returns the number of bits per pixel used by the pixel format
 198  * described by pixdesc.
 199  *
 200  * The returned number of bits refers to the number of bits actually
 201  * used for storing the pixel information, that is padding bits are
 202  * not counted.
 203  */
 204 int av_get_bits_per_pixel(const AVPixFmtDescriptor *pixdesc);
 205
 206 #endif /* AVCODEC_PIXDESC_H */