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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 * jdsample.c
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 *
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 * Copyright (C) 1991-1996, 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 upsampling routines.
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 *
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 * Upsampling input data is counted in "row groups".  A row group
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 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
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 * sample rows of each component.  Upsampling will normally produce
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 * max_v_samp_factor pixel rows from each row group (but this could vary
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 * if the upsampler is applying a scale factor of its own).
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 *
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 * An excellent reference for image resampling is
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 *   Digital Image Warping, George Wolberg, 1990.
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 *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
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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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/* Pointer to routine to upsample a single component */
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typedef JMETHOD(void, upsample1_ptr,
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                (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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                 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));
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/* Private subobject */
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typedef struct {
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  struct jpeg_upsampler pub;    /* public fields */
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  /* Color conversion buffer.  When using separate upsampling and color
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   * conversion steps, this buffer holds one upsampled row group until it
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   * has been color converted and output.
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   * Note: we do not allocate any storage for component(s) which are full-size,
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   * ie do not need rescaling.  The corresponding entry of color_buf[] is
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   * simply set to point to the input data array, thereby avoiding copying.
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   */
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  JSAMPARRAY color_buf[MAX_COMPONENTS];
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  /* Per-component upsampling method pointers */
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  upsample1_ptr methods[MAX_COMPONENTS];
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  int next_row_out;             /* counts rows emitted from color_buf */
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  JDIMENSION rows_to_go;        /* counts rows remaining in image */
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  /* Height of an input row group for each component. */
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  int rowgroup_height[MAX_COMPONENTS];
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  /* These arrays save pixel expansion factors so that int_expand need not
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   * recompute them each time.  They are unused for other upsampling methods.
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   */
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  UINT8 h_expand[MAX_COMPONENTS];
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  UINT8 v_expand[MAX_COMPONENTS];
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} my_upsampler;
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typedef my_upsampler * my_upsample_ptr;
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/*
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 * Initialize for an upsampling pass.
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 */
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METHODDEF(void)
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start_pass_upsample (j_decompress_ptr cinfo)
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{
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  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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  /* Mark the conversion buffer empty */
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  upsample->next_row_out = cinfo->max_v_samp_factor;
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  /* Initialize total-height counter for detecting bottom of image */
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  upsample->rows_to_go = cinfo->output_height;
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}
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/*
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 * Control routine to do upsampling (and color conversion).
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 *
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 * In this version we upsample each component independently.
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 * We upsample one row group into the conversion buffer, then apply
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 * color conversion a row at a time.
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 */
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METHODDEF(void)
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sep_upsample (j_decompress_ptr cinfo,
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              JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
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              JDIMENSION in_row_groups_avail,
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              JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
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              JDIMENSION out_rows_avail)
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{
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  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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  int ci;
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  jpeg_component_info * compptr;
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  JDIMENSION num_rows;
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  /* Fill the conversion buffer, if it's empty */
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  if (upsample->next_row_out >= cinfo->max_v_samp_factor) {
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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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      /* Invoke per-component upsample method.  Notice we pass a POINTER
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       * to color_buf[ci], so that fullsize_upsample can change it.
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       */
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      (*upsample->methods[ci]) (cinfo, compptr,
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        input_buf[ci] + (*in_row_group_ctr * upsample->rowgroup_height[ci]),
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        upsample->color_buf + ci);
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    }
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    upsample->next_row_out = 0;
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  }
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  /* Color-convert and emit rows */
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  /* How many we have in the buffer: */
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  num_rows = (JDIMENSION) (cinfo->max_v_samp_factor - upsample->next_row_out);
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  /* Not more than the distance to the end of the image.  Need this test
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   * in case the image height is not a multiple of max_v_samp_factor:
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   */
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  if (num_rows > upsample->rows_to_go)
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    num_rows = upsample->rows_to_go;
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  /* And not more than what the client can accept: */
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  out_rows_avail -= *out_row_ctr;
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  if (num_rows > out_rows_avail)
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    num_rows = out_rows_avail;
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  (*cinfo->cconvert->color_convert) (cinfo, upsample->color_buf,
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                                     (JDIMENSION) upsample->next_row_out,
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                                     output_buf + *out_row_ctr,
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                                     (int) num_rows);
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  /* Adjust counts */
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  *out_row_ctr += num_rows;
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  upsample->rows_to_go -= num_rows;
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  upsample->next_row_out += num_rows;
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  /* When the buffer is emptied, declare this input row group consumed */
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  if (upsample->next_row_out >= cinfo->max_v_samp_factor)
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    (*in_row_group_ctr)++;
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}
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/*
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 * These are the routines invoked by sep_upsample to upsample pixel values
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 * of a single component.  One row group is processed per call.
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 */
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/*
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 * For full-size components, we just make color_buf[ci] point at the
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 * input buffer, and thus avoid copying any data.  Note that this is
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 * safe only because sep_upsample doesn't declare the input row group
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 * "consumed" until we are done color converting and emitting it.
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 */
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METHODDEF(void)
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fullsize_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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                   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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  *output_data_ptr = input_data;
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}
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/*
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 * This is a no-op version used for "uninteresting" components.
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 * These components will not be referenced by color conversion.
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 */
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METHODDEF(void)
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noop_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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               JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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  *output_data_ptr = NULL;      /* safety check */
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}
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/*
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 * This version handles any integral sampling ratios.
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 * This is not used for typical JPEG files, so it need not be fast.
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 * Nor, for that matter, is it particularly accurate: the algorithm is
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 * simple replication of the input pixel onto the corresponding output
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 * pixels.  The hi-falutin sampling literature refers to this as a
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 * "box filter".  A box filter tends to introduce visible artifacts,
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 * so if you are actually going to use 3:1 or 4:1 sampling ratios
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 * you would be well advised to improve this code.
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 */
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METHODDEF(void)
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int_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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              JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
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  JSAMPARRAY output_data = *output_data_ptr;
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  register JSAMPROW inptr, outptr;
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  register JSAMPLE invalue;
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  register int h;
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  JSAMPROW outend;
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  int h_expand, v_expand;
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  int inrow, outrow;
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  h_expand = upsample->h_expand[compptr->component_index];
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  v_expand = upsample->v_expand[compptr->component_index];
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  inrow = outrow = 0;
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  while (outrow < cinfo->max_v_samp_factor) {
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    /* Generate one output row with proper horizontal expansion */
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    inptr = input_data[inrow];
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    outptr = output_data[outrow];
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    outend = outptr + cinfo->output_width;
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    while (outptr < outend) {
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      invalue = *inptr++;       /* don't need GETJSAMPLE() here */
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      for (h = h_expand; h > 0; h--) {
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        *outptr++ = invalue;
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      }
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    }
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    /* Generate any additional output rows by duplicating the first one */
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    if (v_expand > 1) {
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      jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
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                        v_expand-1, cinfo->output_width);
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    }
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    inrow++;
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    outrow += v_expand;
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  }
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}
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/*
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 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
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 * It's still a box filter.
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 */
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METHODDEF(void)
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h2v1_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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               JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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  JSAMPARRAY output_data = *output_data_ptr;
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  register JSAMPROW inptr, outptr;
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  register JSAMPLE invalue;
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  JSAMPROW outend;
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  int inrow;
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  for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
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    inptr = input_data[inrow];
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    outptr = output_data[inrow];
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    outend = outptr + cinfo->output_width;
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    while (outptr < outend) {
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      invalue = *inptr++;       /* don't need GETJSAMPLE() here */
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      *outptr++ = invalue;
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      *outptr++ = invalue;
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    }
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  }
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}
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/*
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 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
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 * It's still a box filter.
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 */
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METHODDEF(void)
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h2v2_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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               JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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  JSAMPARRAY output_data = *output_data_ptr;
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  register JSAMPROW inptr, outptr;
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  register JSAMPLE invalue;
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  JSAMPROW outend;
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  int inrow, outrow;
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  inrow = outrow = 0;
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  while (outrow < cinfo->max_v_samp_factor) {
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    inptr = input_data[inrow];
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    outptr = output_data[outrow];
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    outend = outptr + cinfo->output_width;
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    while (outptr < outend) {
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      invalue = *inptr++;       /* don't need GETJSAMPLE() here */
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      *outptr++ = invalue;
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      *outptr++ = invalue;
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    }
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    jcopy_sample_rows(output_data, outrow, output_data, outrow+1,
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                      1, cinfo->output_width);
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    inrow++;
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    outrow += 2;
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  }
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}
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/*
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 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical.
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 *
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 * The upsampling algorithm is linear interpolation between pixel centers,
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 * also known as a "triangle filter".  This is a good compromise between
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 * speed and visual quality.  The centers of the output pixels are 1/4 and 3/4
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 * of the way between input pixel centers.
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 *
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 * A note about the "bias" calculations: when rounding fractional values to
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 * integer, we do not want to always round 0.5 up to the next integer.
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 * If we did that, we'd introduce a noticeable bias towards larger values.
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 * Instead, this code is arranged so that 0.5 will be rounded up or down at
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 * alternate pixel locations (a simple ordered dither pattern).
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 */
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METHODDEF(void)
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h2v1_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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                     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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  JSAMPARRAY output_data = *output_data_ptr;
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  register JSAMPROW inptr, outptr;
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  register int invalue;
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  register JDIMENSION colctr;
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  int inrow;
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  for (inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++) {
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    inptr = input_data[inrow];
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    outptr = output_data[inrow];
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    /* Special case for first column */
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    invalue = GETJSAMPLE(*inptr++);
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    *outptr++ = (JSAMPLE) invalue;
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    *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(*inptr) + 2) >> 2);
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    for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
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      /* General case: 3/4 * nearer pixel + 1/4 * further pixel */
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      invalue = GETJSAMPLE(*inptr++) * 3;
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      *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(inptr[-2]) + 1) >> 2);
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      *outptr++ = (JSAMPLE) ((invalue + GETJSAMPLE(*inptr) + 2) >> 2);
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    }
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    /* Special case for last column */
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    invalue = GETJSAMPLE(*inptr);
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    *outptr++ = (JSAMPLE) ((invalue * 3 + GETJSAMPLE(inptr[-1]) + 1) >> 2);
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    *outptr++ = (JSAMPLE) invalue;
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  }
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}
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/*
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 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical.
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 * Again a triangle filter; see comments for h2v1 case, above.
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 *
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 * It is OK for us to reference the adjacent input rows because we demanded
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 * context from the main buffer controller (see initialization code).
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 */
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METHODDEF(void)
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h2v2_fancy_upsample (j_decompress_ptr cinfo, jpeg_component_info * compptr,
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                     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr)
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{
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  JSAMPARRAY output_data = *output_data_ptr;
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  register JSAMPROW inptr0, inptr1, outptr;
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#if BITS_IN_JSAMPLE == 8
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  register int thiscolsum, lastcolsum, nextcolsum;
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#else
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  register INT32 thiscolsum, lastcolsum, nextcolsum;
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#endif
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  register JDIMENSION colctr;
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  int inrow, outrow, v;
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  inrow = outrow = 0;
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  while (outrow < cinfo->max_v_samp_factor) {
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    for (v = 0; v < 2; v++) {
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      /* inptr0 points to nearest input row, inptr1 points to next nearest */
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      inptr0 = input_data[inrow];
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      if (v == 0)               /* next nearest is row above */
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        inptr1 = input_data[inrow-1];
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      else                      /* next nearest is row below */
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        inptr1 = input_data[inrow+1];
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      outptr = output_data[outrow++];
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      /* Special case for first column */
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      thiscolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
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      nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
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      *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 8) >> 4);
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      *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
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      lastcolsum = thiscolsum; thiscolsum = nextcolsum;
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      for (colctr = compptr->downsampled_width - 2; colctr > 0; colctr--) {
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        /* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */
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        /* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */
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        nextcolsum = GETJSAMPLE(*inptr0++) * 3 + GETJSAMPLE(*inptr1++);
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        *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
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        *outptr++ = (JSAMPLE) ((thiscolsum * 3 + nextcolsum + 7) >> 4);
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        lastcolsum = thiscolsum; thiscolsum = nextcolsum;
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      }
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      /* Special case for last column */
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      *outptr++ = (JSAMPLE) ((thiscolsum * 3 + lastcolsum + 8) >> 4);
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      *outptr++ = (JSAMPLE) ((thiscolsum * 4 + 7) >> 4);
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    }
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    inrow++;
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  }
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}
396

397

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/*
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 * Module initialization routine for upsampling.
400
 */
401

402
GLOBAL(void)
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jinit_upsampler (j_decompress_ptr cinfo)
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{
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  my_upsample_ptr upsample;
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  int ci;
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  jpeg_component_info * compptr;
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  boolean need_buffer, do_fancy;
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  int h_in_group, v_in_group, h_out_group, v_out_group;
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  upsample = (my_upsample_ptr)
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    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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                                SIZEOF(my_upsampler));
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  cinfo->upsample = (struct jpeg_upsampler *) upsample;
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  upsample->pub.start_pass = start_pass_upsample;
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  upsample->pub.upsample = sep_upsample;
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  upsample->pub.need_context_rows = FALSE; /* until we find out differently */
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  if (cinfo->CCIR601_sampling)  /* this isn't supported */
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    ERREXIT(cinfo, JERR_CCIR601_NOTIMPL);
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  /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1,
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   * so don't ask for it.
424
   */
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  do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1;
426

427
  /* Verify we can handle the sampling factors, select per-component methods,
428
   * and create storage as needed.
429
   */
430
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
431
       ci++, compptr++) {
432
    /* Compute size of an "input group" after IDCT scaling.  This many samples
433
     * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
434
     */
435
    h_in_group = (compptr->h_samp_factor * compptr->DCT_scaled_size) /
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                 cinfo->min_DCT_scaled_size;
437
    v_in_group = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
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                 cinfo->min_DCT_scaled_size;
439
    h_out_group = cinfo->max_h_samp_factor;
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    v_out_group = cinfo->max_v_samp_factor;
441
    upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
442
    need_buffer = TRUE;
443
    if (! compptr->component_needed) {
444
      /* Don't bother to upsample an uninteresting component. */
445
      upsample->methods[ci] = noop_upsample;
446
      need_buffer = FALSE;
447
    } else if (h_in_group == h_out_group && v_in_group == v_out_group) {
448
      /* Fullsize components can be processed without any work. */
449
      upsample->methods[ci] = fullsize_upsample;
450
      need_buffer = FALSE;
451
    } else if (h_in_group * 2 == h_out_group &&
452
               v_in_group == v_out_group) {
453
      /* Special cases for 2h1v upsampling */
454
      if (do_fancy && compptr->downsampled_width > 2)
455
        upsample->methods[ci] = h2v1_fancy_upsample;
456
      else
457
        upsample->methods[ci] = h2v1_upsample;
458
    } else if (h_in_group * 2 == h_out_group &&
459
               v_in_group * 2 == v_out_group) {
460
      /* Special cases for 2h2v upsampling */
461
      if (do_fancy && compptr->downsampled_width > 2) {
462
        upsample->methods[ci] = h2v2_fancy_upsample;
463
        upsample->pub.need_context_rows = TRUE;
464
      } else
465
        upsample->methods[ci] = h2v2_upsample;
466
    } else if ((h_out_group % h_in_group) == 0 &&
467
               (v_out_group % v_in_group) == 0) {
468
      /* Generic integral-factors upsampling method */
469
      upsample->methods[ci] = int_upsample;
470
      upsample->h_expand[ci] = (UINT8) (h_out_group / h_in_group);
471
      upsample->v_expand[ci] = (UINT8) (v_out_group / v_in_group);
472
    } else
473
      ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
474
    if (need_buffer) {
475
      upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
476
        ((j_common_ptr) cinfo, JPOOL_IMAGE,
477
         (JDIMENSION) jround_up((long) cinfo->output_width,
478
                                (long) cinfo->max_h_samp_factor),
479
         (JDIMENSION) cinfo->max_v_samp_factor);
480
    }
481
  }
482
}
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