jdk

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/*
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 * reserved comment block
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 * DO NOT REMOVE OR ALTER!
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 */
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/*
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 * jcprepct.c
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 *
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 * Copyright (C) 1994-1996, Thomas G. Lane.
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 * This file is part of the Independent JPEG Group's software.
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 * For conditions of distribution and use, see the accompanying README file.
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 *
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 * This file contains the compression preprocessing controller.
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 * This controller manages the color conversion, downsampling,
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 * and edge expansion steps.
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 *
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 * Most of the complexity here is associated with buffering input rows
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 * as required by the downsampler.  See the comments at the head of
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 * jcsample.c for the downsampler's needs.
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 */
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#define JPEG_INTERNALS
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#include "jinclude.h"
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#include "jpeglib.h"
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/* At present, jcsample.c can request context rows only for smoothing.
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 * In the future, we might also need context rows for CCIR601 sampling
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 * or other more-complex downsampling procedures.  The code to support
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 * context rows should be compiled only if needed.
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 */
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#ifdef INPUT_SMOOTHING_SUPPORTED
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#define CONTEXT_ROWS_SUPPORTED
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#endif
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/*
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 * For the simple (no-context-row) case, we just need to buffer one
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 * row group's worth of pixels for the downsampling step.  At the bottom of
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 * the image, we pad to a full row group by replicating the last pixel row.
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 * The downsampler's last output row is then replicated if needed to pad
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 * out to a full iMCU row.
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 *
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 * When providing context rows, we must buffer three row groups' worth of
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 * pixels.  Three row groups are physically allocated, but the row pointer
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 * arrays are made five row groups high, with the extra pointers above and
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 * below "wrapping around" to point to the last and first real row groups.
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 * This allows the downsampler to access the proper context rows.
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 * At the top and bottom of the image, we create dummy context rows by
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 * copying the first or last real pixel row.  This copying could be avoided
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 * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the
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 * trouble on the compression side.
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 */
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/* Private buffer controller object */
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typedef struct {
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  struct jpeg_c_prep_controller pub; /* public fields */
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  /* Downsampling input buffer.  This buffer holds color-converted data
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   * until we have enough to do a downsample step.
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   */
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  JSAMPARRAY color_buf[MAX_COMPONENTS];
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  JDIMENSION rows_to_go;        /* counts rows remaining in source image */
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  int next_buf_row;             /* index of next row to store in color_buf */
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#ifdef CONTEXT_ROWS_SUPPORTED   /* only needed for context case */
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  int this_row_group;           /* starting row index of group to process */
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  int next_buf_stop;            /* downsample when we reach this index */
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#endif
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} my_prep_controller;
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typedef my_prep_controller * my_prep_ptr;
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/*
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 * Initialize for a processing pass.
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 */
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METHODDEF(void)
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start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
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{
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  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
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  if (pass_mode != JBUF_PASS_THRU)
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    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
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  /* Initialize total-height counter for detecting bottom of image */
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  prep->rows_to_go = cinfo->image_height;
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  /* Mark the conversion buffer empty */
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  prep->next_buf_row = 0;
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#ifdef CONTEXT_ROWS_SUPPORTED
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  /* Preset additional state variables for context mode.
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   * These aren't used in non-context mode, so we needn't test which mode.
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   */
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  prep->this_row_group = 0;
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  /* Set next_buf_stop to stop after two row groups have been read in. */
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  prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;
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#endif
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}
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/*
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 * Expand an image vertically from height input_rows to height output_rows,
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 * by duplicating the bottom row.
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 */
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LOCAL(void)
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expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,
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                    int input_rows, int output_rows)
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{
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  register int row;
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  for (row = input_rows; row < output_rows; row++) {
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    jcopy_sample_rows(image_data, input_rows-1, image_data, row,
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                      1, num_cols);
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  }
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}
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/*
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 * Process some data in the simple no-context case.
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 *
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 * Preprocessor output data is counted in "row groups".  A row group
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 * is defined to be v_samp_factor sample rows of each component.
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 * Downsampling will produce this much data from each max_v_samp_factor
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 * input rows.
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 */
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METHODDEF(void)
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pre_process_data (j_compress_ptr cinfo,
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                  JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
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                  JDIMENSION in_rows_avail,
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                  JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
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                  JDIMENSION out_row_groups_avail)
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{
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  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
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  int numrows, ci;
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  JDIMENSION inrows;
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  jpeg_component_info * compptr;
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  while (*in_row_ctr < in_rows_avail &&
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         *out_row_group_ctr < out_row_groups_avail) {
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    /* Do color conversion to fill the conversion buffer. */
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    inrows = in_rows_avail - *in_row_ctr;
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    numrows = cinfo->max_v_samp_factor - prep->next_buf_row;
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    numrows = (int) MIN((JDIMENSION) numrows, inrows);
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    (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
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                                       prep->color_buf,
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                                       (JDIMENSION) prep->next_buf_row,
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                                       numrows);
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    *in_row_ctr += numrows;
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    prep->next_buf_row += numrows;
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    prep->rows_to_go -= numrows;
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    /* If at bottom of image, pad to fill the conversion buffer. */
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    if (prep->rows_to_go == 0 &&
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        prep->next_buf_row < cinfo->max_v_samp_factor) {
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      for (ci = 0; ci < cinfo->num_components; ci++) {
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        expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
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                           prep->next_buf_row, cinfo->max_v_samp_factor);
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      }
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      prep->next_buf_row = cinfo->max_v_samp_factor;
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    }
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    /* If we've filled the conversion buffer, empty it. */
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    if (prep->next_buf_row == cinfo->max_v_samp_factor) {
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      (*cinfo->downsample->downsample) (cinfo,
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                                        prep->color_buf, (JDIMENSION) 0,
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                                        output_buf, *out_row_group_ctr);
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      prep->next_buf_row = 0;
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      (*out_row_group_ctr)++;
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    }
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    /* If at bottom of image, pad the output to a full iMCU height.
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     * Note we assume the caller is providing a one-iMCU-height output buffer!
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     */
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    if (prep->rows_to_go == 0 &&
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        *out_row_group_ctr < out_row_groups_avail) {
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      for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
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           ci++, compptr++) {
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        expand_bottom_edge(output_buf[ci],
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                           compptr->width_in_blocks * DCTSIZE,
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                           (int) (*out_row_group_ctr * compptr->v_samp_factor),
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                           (int) (out_row_groups_avail * compptr->v_samp_factor));
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      }
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      *out_row_group_ctr = out_row_groups_avail;
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      break;                    /* can exit outer loop without test */
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    }
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  }
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}
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#ifdef CONTEXT_ROWS_SUPPORTED
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/*
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 * Process some data in the context case.
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 */
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METHODDEF(void)
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pre_process_context (j_compress_ptr cinfo,
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                     JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
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                     JDIMENSION in_rows_avail,
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                     JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
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                     JDIMENSION out_row_groups_avail)
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{
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  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
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  int numrows, ci;
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  int buf_height = cinfo->max_v_samp_factor * 3;
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  JDIMENSION inrows;
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  while (*out_row_group_ctr < out_row_groups_avail) {
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    if (*in_row_ctr < in_rows_avail) {
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      /* Do color conversion to fill the conversion buffer. */
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      inrows = in_rows_avail - *in_row_ctr;
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      numrows = prep->next_buf_stop - prep->next_buf_row;
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      numrows = (int) MIN((JDIMENSION) numrows, inrows);
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      (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
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                                         prep->color_buf,
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                                         (JDIMENSION) prep->next_buf_row,
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                                         numrows);
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      /* Pad at top of image, if first time through */
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      if (prep->rows_to_go == cinfo->image_height) {
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        for (ci = 0; ci < cinfo->num_components; ci++) {
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          int row;
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          for (row = 1; row <= cinfo->max_v_samp_factor; row++) {
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            jcopy_sample_rows(prep->color_buf[ci], 0,
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                              prep->color_buf[ci], -row,
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                              1, cinfo->image_width);
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          }
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        }
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      }
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      *in_row_ctr += numrows;
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      prep->next_buf_row += numrows;
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      prep->rows_to_go -= numrows;
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    } else {
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      /* Return for more data, unless we are at the bottom of the image. */
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      if (prep->rows_to_go != 0)
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        break;
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      /* When at bottom of image, pad to fill the conversion buffer. */
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      if (prep->next_buf_row < prep->next_buf_stop) {
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        for (ci = 0; ci < cinfo->num_components; ci++) {
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          expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
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                             prep->next_buf_row, prep->next_buf_stop);
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        }
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        prep->next_buf_row = prep->next_buf_stop;
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      }
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    }
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    /* If we've gotten enough data, downsample a row group. */
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    if (prep->next_buf_row == prep->next_buf_stop) {
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      (*cinfo->downsample->downsample) (cinfo,
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                                        prep->color_buf,
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                                        (JDIMENSION) prep->this_row_group,
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                                        output_buf, *out_row_group_ctr);
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      (*out_row_group_ctr)++;
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      /* Advance pointers with wraparound as necessary. */
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      prep->this_row_group += cinfo->max_v_samp_factor;
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      if (prep->this_row_group >= buf_height)
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        prep->this_row_group = 0;
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      if (prep->next_buf_row >= buf_height)
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        prep->next_buf_row = 0;
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      prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;
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    }
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  }
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}
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/*
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 * Create the wrapped-around downsampling input buffer needed for context mode.
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 */
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LOCAL(void)
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create_context_buffer (j_compress_ptr cinfo)
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{
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  my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
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  int rgroup_height = cinfo->max_v_samp_factor;
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  int ci, i;
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  jpeg_component_info * compptr;
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  JSAMPARRAY true_buffer, fake_buffer;
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  /* Grab enough space for fake row pointers for all the components;
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   * we need five row groups' worth of pointers for each component.
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   */
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  fake_buffer = (JSAMPARRAY)
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    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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                                (cinfo->num_components * 5 * rgroup_height) *
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                                SIZEOF(JSAMPROW));
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  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
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       ci++, compptr++) {
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    /* Allocate the actual buffer space (3 row groups) for this component.
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     * We make the buffer wide enough to allow the downsampler to edge-expand
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     * horizontally within the buffer, if it so chooses.
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     */
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    true_buffer = (*cinfo->mem->alloc_sarray)
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      ((j_common_ptr) cinfo, JPOOL_IMAGE,
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       (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *
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                      cinfo->max_h_samp_factor) / compptr->h_samp_factor),
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       (JDIMENSION) (3 * rgroup_height));
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    /* Copy true buffer row pointers into the middle of the fake row array */
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    MEMCOPY(fake_buffer + rgroup_height, true_buffer,
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            3 * rgroup_height * SIZEOF(JSAMPROW));
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    /* Fill in the above and below wraparound pointers */
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    for (i = 0; i < rgroup_height; i++) {
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      fake_buffer[i] = true_buffer[2 * rgroup_height + i];
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      fake_buffer[4 * rgroup_height + i] = true_buffer[i];
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    }
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    prep->color_buf[ci] = fake_buffer + rgroup_height;
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    fake_buffer += 5 * rgroup_height; /* point to space for next component */
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  }
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}
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#endif /* CONTEXT_ROWS_SUPPORTED */
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/*
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 * Initialize preprocessing controller.
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 */
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GLOBAL(void)
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jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)
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{
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  my_prep_ptr prep;
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  int ci;
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  jpeg_component_info * compptr;
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  if (need_full_buffer)         /* safety check */
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    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
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  prep = (my_prep_ptr)
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    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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                                SIZEOF(my_prep_controller));
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  cinfo->prep = (struct jpeg_c_prep_controller *) prep;
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  prep->pub.start_pass = start_pass_prep;
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  /* Allocate the color conversion buffer.
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   * We make the buffer wide enough to allow the downsampler to edge-expand
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   * horizontally within the buffer, if it so chooses.
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   */
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  if (cinfo->downsample->need_context_rows) {
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    /* Set up to provide context rows */
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#ifdef CONTEXT_ROWS_SUPPORTED
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    prep->pub.pre_process_data = pre_process_context;
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    create_context_buffer(cinfo);
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#else
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    ERREXIT(cinfo, JERR_NOT_COMPILED);
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#endif
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  } else {
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    /* No context, just make it tall enough for one row group */
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    prep->pub.pre_process_data = pre_process_data;
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    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
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         ci++, compptr++) {
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      prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)
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        ((j_common_ptr) cinfo, JPOOL_IMAGE,
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         (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *
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                        cinfo->max_h_samp_factor) / compptr->h_samp_factor),
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         (JDIMENSION) cinfo->max_v_samp_factor);
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    }
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  }
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}
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