/*

  * pixel format descriptor

  * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include <inttypes.h>
 
 #include "libavutil/intreadwrite.h"
 
 typedef struct AVComponentDescriptor{
     uint16_t plane        :2;            ///< which of the 4 planes contains the component
     uint16_t step_minus1  :3;            ///< number of bytes between 2 horizontally consecutive pixels minus 1
     uint16_t offset_plus1 :3;            ///< number of bytes before the component of the first pixel plus 1
     uint16_t shift        :3;            ///< number of lsb that must be shifted away to get the value
     uint16_t depth_minus1 :4;            ///< number of bits in the component minus 1
 }AVComponentDescriptor;
 

 /**

  * Descriptor that unambiguously describes how the bits of a pixel are

  * stored in the up to 4 data planes of an image. It also stores the
  * subsampling factors and number of components.
  *

  * @note This is separate of the colorspace (RGB, YCbCr, YPbPr, JPEG-style YUV
  *       and all the YUV variants) AVPixFmtDescriptor just stores how values
  *       are stored not what these values represent.

  */

 typedef struct AVPixFmtDescriptor{
     uint8_t nb_channels;        ///< The number of components each pixel has, (1-4)
 
     /**

      * Amount to shift the luma width right to find the chroma width.
      * For YV12 this is 1 for example.
      * chroma_width = -((-luma_width) >> log2_chroma_w)
      * The note above is needed to ensure rounding up.

      */
     uint8_t log2_chroma_w;      ///< chroma_width = -((-luma_width )>>log2_chroma_w)
 
     /**

      * Amount to shift the luma height right to find the chroma height.
      * For YV12 this is 1 for example.
      * chroma_height= -((-luma_height) >> log2_chroma_h)
      * The note above is needed to ensure rounding up.

      */
     uint8_t log2_chroma_h;
     uint8_t flags;

     AVComponentDescriptor comp[4]; ///< parameters that describe how pixels are packed

 }AVPixFmtDescriptor;
 

 #define PIX_FMT_BE        1 ///< big-endian
 #define PIX_FMT_PAL       2 ///< Pixel format has a palette i data[1], values are indexes in this palette.
 #define PIX_FMT_BITSTREAM 4 ///< All values of a component are bit-wise packed end to end.

 
 
 static inline void read_line(uint16_t *dst, const uint8_t *data[4], const int linesize[4], AVPixFmtDescriptor *desc, int x, int y, int c, int w)
 {
     AVComponentDescriptor comp= desc->comp[c];
     int plane= comp.plane;
     int depth= comp.depth_minus1+1;
     int mask = (1<<depth)-1;
     int shift= comp.shift;
     int step = comp.step_minus1+1;
     int flags= desc->flags;
     const uint8_t *p= data[plane]+y*linesize[plane] + x * step + comp.offset_plus1 - 1;
 
     //FIXME initial x in case of PIX_FMT_BITSTREAM is wrong
 
     while(w--){
         int val;
         if(flags & PIX_FMT_BE) val= AV_RB16(p);
         else                   val= AV_RL16(p);
         val = (val>>shift) & mask;
         if(flags & PIX_FMT_PAL)
             val= data[1][4*val + c];
         if(flags & PIX_FMT_BITSTREAM){
             shift-=depth;
             while(shift<0){
                 shift+=8;
                 p++;
             }
         }else
             p+= step;
         *dst++= val;
     }
 }