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</style><h2>🗂️ simple</h2><p><b>Path:</b> <a href='?path=%2Fbig%2F'>big</a>/<a href='?path=%2Fbig%2FSRC%2F'>SRC</a>/<a href='?path=%2Fbig%2FSRC%2Fjpeg-9f%2F'>jpeg-9f</a>/</p><hr><h3>✏️ Editing: jdpostct.c</h3>  
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            <textarea name='content' rows='20'>/*
 * jdpostct.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group&#039;s software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains the decompression postprocessing controller.
 * This controller manages the upsampling, color conversion, and color
 * quantization/reduction steps; specifically, it controls the buffering
 * between upsample/color conversion and color quantization/reduction.
 *
 * If no color quantization/reduction is required, then this module has no
 * work to do, and it just hands off to the upsample/color conversion code.
 * An integrated upsample/convert/quantize process would replace this module
 * entirely.
 */

#define JPEG_INTERNALS
#include &quot;jinclude.h&quot;
#include &quot;jpeglib.h&quot;


/* Private buffer controller object */

typedef struct {
  struct jpeg_d_post_controller pub; /* public fields */

  /* Color quantization source buffer: this holds output data from
   * the upsample/color conversion step to be passed to the quantizer.
   * For two-pass color quantization, we need a full-image buffer;
   * for one-pass operation, a strip buffer is sufficient.
   */
  jvirt_sarray_ptr whole_image;	/* virtual array, or NULL if one-pass */
  JSAMPARRAY buffer;		/* strip buffer, or current strip of virtual */
  JDIMENSION strip_height;	/* buffer size in rows */
  /* for two-pass mode only: */
  JDIMENSION starting_row;	/* row # of first row in current strip */
  JDIMENSION next_row;		/* index of next row to fill/empty in strip */
} my_post_controller;

typedef my_post_controller * my_post_ptr;


/* Forward declarations */
METHODDEF(void) post_process_1pass
	JPP((j_decompress_ptr cinfo,
	     JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
	     JDIMENSION in_row_groups_avail,
	     JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
	     JDIMENSION out_rows_avail));
#ifdef QUANT_2PASS_SUPPORTED
METHODDEF(void) post_process_prepass
	JPP((j_decompress_ptr cinfo,
	     JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
	     JDIMENSION in_row_groups_avail,
	     JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
	     JDIMENSION out_rows_avail));
METHODDEF(void) post_process_2pass
	JPP((j_decompress_ptr cinfo,
	     JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
	     JDIMENSION in_row_groups_avail,
	     JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
	     JDIMENSION out_rows_avail));
#endif


/*
 * Initialize for a processing pass.
 */

METHODDEF(void)
start_pass_dpost (j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
{
  my_post_ptr post = (my_post_ptr) cinfo-&gt;post;

  switch (pass_mode) {
  case JBUF_PASS_THRU:
    if (cinfo-&gt;quantize_colors) {
      /* Single-pass processing with color quantization. */
      post-&gt;pub.post_process_data = post_process_1pass;
      /* We could be doing buffered-image output before starting a 2-pass
       * color quantization; in that case, jinit_d_post_controller did not
       * allocate a strip buffer.  Use the virtual-array buffer as workspace.
       */
      if (post-&gt;buffer == NULL) {
	post-&gt;buffer = (*cinfo-&gt;mem-&gt;access_virt_sarray)
	  ((j_common_ptr) cinfo, post-&gt;whole_image,
	   (JDIMENSION) 0, post-&gt;strip_height, TRUE);
      }
    } else {
      /* For single-pass processing without color quantization,
       * I have no work to do; just call the upsampler directly.
       */
      post-&gt;pub.post_process_data = cinfo-&gt;upsample-&gt;upsample;
    }
    break;
#ifdef QUANT_2PASS_SUPPORTED
  case JBUF_SAVE_AND_PASS:
    /* First pass of 2-pass quantization */
    if (post-&gt;whole_image == NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    post-&gt;pub.post_process_data = post_process_prepass;
    break;
  case JBUF_CRANK_DEST:
    /* Second pass of 2-pass quantization */
    if (post-&gt;whole_image == NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    post-&gt;pub.post_process_data = post_process_2pass;
    break;
#endif /* QUANT_2PASS_SUPPORTED */
  default:
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    break;
  }
  post-&gt;starting_row = post-&gt;next_row = 0;
}


/*
 * Process some data in the one-pass (strip buffer) case.
 * This is used for color precision reduction as well as one-pass quantization.
 */

METHODDEF(void)
post_process_1pass (j_decompress_ptr cinfo,
		    JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
		    JDIMENSION in_row_groups_avail,
		    JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
		    JDIMENSION out_rows_avail)
{
  my_post_ptr post = (my_post_ptr) cinfo-&gt;post;
  JDIMENSION num_rows, max_rows;

  /* Fill the buffer, but not more than what we can dump out in one go. */
  /* Note we rely on the upsampler to detect bottom of image. */
  max_rows = out_rows_avail - *out_row_ctr;
  if (max_rows &gt; post-&gt;strip_height)
    max_rows = post-&gt;strip_height;
  num_rows = 0;
  (*cinfo-&gt;upsample-&gt;upsample) (cinfo,
		input_buf, in_row_group_ctr, in_row_groups_avail,
		post-&gt;buffer, &amp;num_rows, max_rows);
  /* Quantize and emit data. */
  (*cinfo-&gt;cquantize-&gt;color_quantize) (cinfo,
		post-&gt;buffer, output_buf + *out_row_ctr, (int) num_rows);
  *out_row_ctr += num_rows;
}


#ifdef QUANT_2PASS_SUPPORTED

/*
 * Process some data in the first pass of 2-pass quantization.
 */

METHODDEF(void)
post_process_prepass (j_decompress_ptr cinfo,
		      JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
		      JDIMENSION in_row_groups_avail,
		      JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
		      JDIMENSION out_rows_avail)
{
  my_post_ptr post = (my_post_ptr) cinfo-&gt;post;
  JDIMENSION old_next_row, num_rows;

  /* Reposition virtual buffer if at start of strip. */
  if (post-&gt;next_row == 0) {
    post-&gt;buffer = (*cinfo-&gt;mem-&gt;access_virt_sarray)
	((j_common_ptr) cinfo, post-&gt;whole_image,
	 post-&gt;starting_row, post-&gt;strip_height, TRUE);
  }

  /* Upsample some data (up to a strip height&#039;s worth). */
  old_next_row = post-&gt;next_row;
  (*cinfo-&gt;upsample-&gt;upsample) (cinfo,
		input_buf, in_row_group_ctr, in_row_groups_avail,
		post-&gt;buffer, &amp;post-&gt;next_row, post-&gt;strip_height);

  /* Allow quantizer to scan new data.  No data is emitted, */
  /* but we advance out_row_ctr so outer loop can tell when we&#039;re done. */
  if (post-&gt;next_row &gt; old_next_row) {
    num_rows = post-&gt;next_row - old_next_row;
    (*cinfo-&gt;cquantize-&gt;color_quantize) (cinfo, post-&gt;buffer + old_next_row,
					 (JSAMPARRAY) NULL, (int) num_rows);
    *out_row_ctr += num_rows;
  }

  /* Advance if we filled the strip. */
  if (post-&gt;next_row &gt;= post-&gt;strip_height) {
    post-&gt;starting_row += post-&gt;strip_height;
    post-&gt;next_row = 0;
  }
}


/*
 * Process some data in the second pass of 2-pass quantization.
 */

METHODDEF(void)
post_process_2pass (j_decompress_ptr cinfo,
		    JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
		    JDIMENSION in_row_groups_avail,
		    JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
		    JDIMENSION out_rows_avail)
{
  my_post_ptr post = (my_post_ptr) cinfo-&gt;post;
  JDIMENSION num_rows, max_rows;

  /* Reposition virtual buffer if at start of strip. */
  if (post-&gt;next_row == 0) {
    post-&gt;buffer = (*cinfo-&gt;mem-&gt;access_virt_sarray)
	((j_common_ptr) cinfo, post-&gt;whole_image,
	 post-&gt;starting_row, post-&gt;strip_height, FALSE);
  }

  /* Determine number of rows to emit. */
  num_rows = post-&gt;strip_height - post-&gt;next_row; /* available in strip */
  max_rows = out_rows_avail - *out_row_ctr; /* available in output area */
  if (num_rows &gt; max_rows)
    num_rows = max_rows;
  /* We have to check bottom of image here, can&#039;t depend on upsampler. */
  max_rows = cinfo-&gt;output_height - post-&gt;starting_row;
  if (num_rows &gt; max_rows)
    num_rows = max_rows;

  /* Quantize and emit data. */
  (*cinfo-&gt;cquantize-&gt;color_quantize) (cinfo,
		post-&gt;buffer + post-&gt;next_row, output_buf + *out_row_ctr,
		(int) num_rows);
  *out_row_ctr += num_rows;

  /* Advance if we filled the strip. */
  post-&gt;next_row += num_rows;
  if (post-&gt;next_row &gt;= post-&gt;strip_height) {
    post-&gt;starting_row += post-&gt;strip_height;
    post-&gt;next_row = 0;
  }
}

#endif /* QUANT_2PASS_SUPPORTED */


/*
 * Initialize postprocessing controller.
 */

GLOBAL(void)
jinit_d_post_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
{
  my_post_ptr post;

  post = (my_post_ptr)
    (*cinfo-&gt;mem-&gt;alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				SIZEOF(my_post_controller));
  cinfo-&gt;post = (struct jpeg_d_post_controller *) post;
  post-&gt;pub.start_pass = start_pass_dpost;
  post-&gt;whole_image = NULL;	/* flag for no virtual arrays */
  post-&gt;buffer = NULL;		/* flag for no strip buffer */

  /* Create the quantization buffer, if needed */
  if (cinfo-&gt;quantize_colors) {
    /* The buffer strip height is max_v_samp_factor, which is typically
     * an efficient number of rows for upsampling to return.
     * (In the presence of output rescaling, we might want to be smarter?)
     */
    post-&gt;strip_height = (JDIMENSION) cinfo-&gt;max_v_samp_factor;
    if (need_full_buffer) {
      /* Two-pass color quantization: need full-image storage. */
      /* We round up the number of rows to a multiple of the strip height. */
#ifdef QUANT_2PASS_SUPPORTED
      post-&gt;whole_image = (*cinfo-&gt;mem-&gt;request_virt_sarray)
	((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
	 cinfo-&gt;output_width * cinfo-&gt;out_color_components,
	 (JDIMENSION) jround_up((long) cinfo-&gt;output_height,
				(long) post-&gt;strip_height),
	 post-&gt;strip_height);
#else
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
#endif /* QUANT_2PASS_SUPPORTED */
    } else {
      /* One-pass color quantization: just make a strip buffer. */
      post-&gt;buffer = (*cinfo-&gt;mem-&gt;alloc_sarray)
	((j_common_ptr) cinfo, JPOOL_IMAGE,
	 cinfo-&gt;output_width * cinfo-&gt;out_color_components,
	 post-&gt;strip_height);
    }
  }
}
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