media/libjpeg/jdcoefct.h

   1 /*
   2  * jdcoefct.h
   3  *
   4  * This file was part of the Independent JPEG Group's software:
   5  * Copyright (C) 1994-1997, Thomas G. Lane.
   6  * libjpeg-turbo Modifications:
   7  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
   8  * For conditions of distribution and use, see the accompanying README.ijg
   9  * file.
  10  */
  11
  12 #define JPEG_INTERNALS
  13 #include "jpeglib.h"
  14
  15
  16 /* Block smoothing is only applicable for progressive JPEG, so: */
  17 #ifndef D_PROGRESSIVE_SUPPORTED
  18 #undef BLOCK_SMOOTHING_SUPPORTED
  19 #endif
  20
  21
  22 /* Private buffer controller object */
  23
  24 typedef struct {
  25   struct jpeg_d_coef_controller pub; /* public fields */
  26
  27   /* These variables keep track of the current location of the input side. */
  28   /* cinfo->input_iMCU_row is also used for this. */
  29   JDIMENSION MCU_ctr;           /* counts MCUs processed in current row */
  30   int MCU_vert_offset;          /* counts MCU rows within iMCU row */
  31   int MCU_rows_per_iMCU_row;    /* number of such rows needed */
  32
  33   /* The output side's location is represented by cinfo->output_iMCU_row. */
  34
  35   /* In single-pass modes, it's sufficient to buffer just one MCU.
  36    * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
  37    * and let the entropy decoder write into that workspace each time.
  38    * In multi-pass modes, this array points to the current MCU's blocks
  39    * within the virtual arrays; it is used only by the input side.
  40    */
  41   JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];
  42
  43   /* Temporary workspace for one MCU */
  44   JCOEF *workspace;
  45
  46 #ifdef D_MULTISCAN_FILES_SUPPORTED
  47   /* In multi-pass modes, we need a virtual block array for each component. */
  48   jvirt_barray_ptr whole_image[MAX_COMPONENTS];
  49 #endif
  50
  51 #ifdef BLOCK_SMOOTHING_SUPPORTED
  52   /* When doing block smoothing, we latch coefficient Al values here */
  53   int *coef_bits_latch;
  54 #define SAVED_COEFS  6          /* we save coef_bits[0..5] */
  55 #endif
  56 } my_coef_controller;
  57
  58 typedef my_coef_controller *my_coef_ptr;
  59
  60
  61 LOCAL(void)
  62 start_iMCU_row(j_decompress_ptr cinfo)
  63 /* Reset within-iMCU-row counters for a new row (input side) */
  64 {
  65   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
  66
  67   /* In an interleaved scan, an MCU row is the same as an iMCU row.
  68    * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
  69    * But at the bottom of the image, process only what's left.
  70    */
  71   if (cinfo->comps_in_scan > 1) {
  72     coef->MCU_rows_per_iMCU_row = 1;
  73   } else {
  74     if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows - 1))
  75       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
  76     else
  77       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
  78   }
  79
  80   coef->MCU_ctr = 0;
  81   coef->MCU_vert_offset = 0;
  82 }