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_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 #define PIX_FMT_HWACCEL   8 ///< Pixel format is an HW accelerated format.
  83
  84 /**
  85  * The array of all the pixel format descriptors.
  86  */
  87 extern const AVPixFmtDescriptor av_pix_fmt_descriptors[];
  88
  89 /**
  90  * Reads a line from an image, and writes to dst the values of the
  91  * pixel format component c.
  92  *
  93  * @param data the array containing the pointers to the planes of the image
  94  * @param linesizes the array containing the linesizes of the image
  95  * @param desc the pixel format descriptor for the image
  96  * @param x the horizontal coordinate of the first pixel to read
  97  * @param y the vertical coordinate of the first pixel to read
  98  * @param w the width of the line to read, that is the number of
  99  * values to write to dst
 100  * @param read_pal_component if not zero and the format is a paletted
 101  * format writes to dst the values corresponding to the palette
 102  * component c in data[1], rather than the palette indexes in
 103  * data[0]. The behavior is undefined if the format is not paletted.
 104  */
 105 static inline void read_line(uint16_t *dst, const uint8_t *data[4], const int linesize[4],
 106                              const AVPixFmtDescriptor *desc, int x, int y, int c, int w, int read_pal_component)
 107 {
 108     AVComponentDescriptor comp= desc->comp[c];
 109     int plane= comp.plane;
 110     int depth= comp.depth_minus1+1;
 111     int mask = (1<<depth)-1;
 112     int shift= comp.shift;
 113     int step = comp.step_minus1+1;
 114     int flags= desc->flags;
 115
 116     if (flags & PIX_FMT_BITSTREAM){
 117         int skip = x*step + comp.offset_plus1-1;
 118         const uint8_t *p = data[plane] + y*linesize[plane] + (skip>>3);
 119         int shift = 8 - depth - (skip&7);
 120
 121         while(w--){
 122             int val = (*p >> shift) & mask;
 123             if(read_pal_component)
 124                 val= data[1][4*val + c];
 125             shift -= step;
 126             p -= shift>>3;
 127             shift &= 7;
 128             *dst++= val;
 129         }
 130     } else {
 131         const uint8_t *p = data[plane]+ y*linesize[plane] + x*step + comp.offset_plus1-1;
 132
 133         while(w--){
 134             int val;
 135             if(flags & PIX_FMT_BE) val= AV_RB16(p);
 136             else                   val= AV_RL16(p);
 137             val = (val>>shift) & mask;
 138             if(read_pal_component)
 139                 val= data[1][4*val + c];
 140             p+= step;
 141             *dst++= val;
 142         }
 143     }
 144 }
 145
 146 /**
 147  * Writes the values from src to the pixel format component c of an
 148  * image line.
 149  *
 150  * @param src array containing the values to write
 151  * @param data the array containing the pointers to the planes of the
 152  * image to write into. It is supposed to be zeroed.
 153  * @param linesizes the array containing the linesizes of the image
 154  * @param desc the pixel format descriptor for the image
 155  * @param x the horizontal coordinate of the first pixel to write
 156  * @param y the vertical coordinate of the first pixel to write
 157  * @param w the width of the line to write, that is the number of
 158  * values to write to the image line
 159  */
 160 static inline void write_line(const uint16_t *src, uint8_t *data[4], const int linesize[4],
 161                               const AVPixFmtDescriptor *desc, int x, int y, int c, int w)
 162 {
 163     AVComponentDescriptor comp = desc->comp[c];
 164     int plane = comp.plane;
 165     int depth = comp.depth_minus1+1;
 166     int step  = comp.step_minus1+1;
 167     int flags = desc->flags;
 168
 169     if (flags & PIX_FMT_BITSTREAM) {
 170         int skip = x*step + comp.offset_plus1-1;
 171         uint8_t *p = data[plane] + y*linesize[plane] + (skip>>3);
 172         int shift = 8 - depth - (skip&7);
 173
 174         while (w--) {
 175             *p |= *src++ << shift;
 176             shift -= step;
 177             p -= shift>>3;
 178             shift &= 7;
 179         }
 180     } else {
 181         int shift = comp.shift;
 182         uint8_t *p = data[plane]+ y*linesize[plane] + x*step + comp.offset_plus1-1;
 183
 184         while (w--) {
 185             if (flags & PIX_FMT_BE) {
 186                 uint16_t val = AV_RB16(p) | (*src++<<shift);
 187                 AV_WB16(p, val);
 188             } else {
 189                 uint16_t val = AV_RL16(p) | (*src++<<shift);
 190                 AV_WL16(p, val);
 191             }
 192             p+= step;
 193         }
 194     }
 195 }
 196
 197 /**
 198  * Returns the number of bits per pixel used by the pixel format
 199  * described by pixdesc.
 200  *
 201  * The returned number of bits refers to the number of bits actually
 202  * used for storing the pixel information, that is padding bits are
 203  * not counted.
 204  */
 205 int av_get_bits_per_pixel(const AVPixFmtDescriptor *pixdesc);
 206
 207 #endif /* AVUTIL_PIXDESC_H */