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  * Copyright (C) 2020, Google, Inc.
   9  * For conditions of distribution and use, see the accompanying README.ijg
  10  * file.
  11  */
  12
  13 #define JPEG_INTERNALS
  14 #include "jpeglib.h"
  15
  16
  17 /* Block smoothing is only applicable for progressive JPEG, so: */
  18 #ifndef D_PROGRESSIVE_SUPPORTED
  19 #undef BLOCK_SMOOTHING_SUPPORTED
  20 #endif
  21
  22
  23 /* Private buffer controller object */
  24
  25 typedef struct {
  26   struct jpeg_d_coef_controller pub; /* public fields */
  27
  28   /* These variables keep track of the current location of the input side. */
  29   /* cinfo->input_iMCU_row is also used for this. */
  30   JDIMENSION MCU_ctr;           /* counts MCUs processed in current row */
  31   int MCU_vert_offset;          /* counts MCU rows within iMCU row */
  32   int MCU_rows_per_iMCU_row;    /* number of such rows needed */
  33
  34   /* The output side's location is represented by cinfo->output_iMCU_row. */
  35
  36   /* In single-pass modes, it's sufficient to buffer just one MCU.
  37    * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
  38    * and let the entropy decoder write into that workspace each time.
  39    * In multi-pass modes, this array points to the current MCU's blocks
  40    * within the virtual arrays; it is used only by the input side.
  41    */
  42   JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];
  43
  44   /* Temporary workspace for one MCU */
  45   JCOEF *workspace;
  46
  47 #ifdef D_MULTISCAN_FILES_SUPPORTED
  48   /* In multi-pass modes, we need a virtual block array for each component. */
  49   jvirt_barray_ptr whole_image[MAX_COMPONENTS];
  50 #endif
  51
  52 #ifdef BLOCK_SMOOTHING_SUPPORTED
  53   /* When doing block smoothing, we latch coefficient Al values here */
  54   int *coef_bits_latch;
  55 #define SAVED_COEFS  10         /* we save coef_bits[0..9] */
  56 #endif
  57 } my_coef_controller;
  58
  59 typedef my_coef_controller *my_coef_ptr;
  60
  61
  62 LOCAL(void)
  63 start_iMCU_row(j_decompress_ptr cinfo)
  64 /* Reset within-iMCU-row counters for a new row (input side) */
  65 {
  66   my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
  67
  68   /* In an interleaved scan, an MCU row is the same as an iMCU row.
  69    * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
  70    * But at the bottom of the image, process only what's left.
  71    */
  72   if (cinfo->comps_in_scan > 1) {
  73     coef->MCU_rows_per_iMCU_row = 1;
  74   } else {
  75     if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows - 1))
  76       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
  77     else
  78       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
  79   }
  80
  81   coef->MCU_ctr = 0;
  82   coef->MCU_vert_offset = 0;
  83 }