//  * jdpostct.c
//  *
//  * Copyright (C) 1994-1995, Thomas G. Lane.
//  * This file is part of the Independent JPEG Group'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 "JINCLUDE.h"
#include "JPEGLIB.h"


// 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->post;

  switch (pass_mode) {
  case JBUF_PASS_THRU:
    if (cinfo->quantize_colors) {
      // Single-pass processing with color quantization. 
      post->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->buffer == NULL) {
	post->buffer = (*cinfo->mem->access_virt_sarray)
	  ((j_common_ptr) cinfo, post->whole_image,
	   (JDIMENSION) 0, post->strip_height, TRUE);
      }
    } else {
//  For single-pass processing without color quantization,
//        * I have no work to do; just call the upsampler directly.
      post->pub.post_process_data = cinfo->upsample->upsample;
    }
    break;
#ifdef QUANT_2PASS_SUPPORTED
  case JBUF_SAVE_AND_PASS:
    // First pass of 2-pass quantization 
    if (post->whole_image == NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    post->pub.post_process_data = post_process_prepass;
    break;
  case JBUF_CRANK_DEST:
    // Second pass of 2-pass quantization 
    if (post->whole_image == NULL)
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    post->pub.post_process_data = post_process_2pass;
    break;
#endif // QUANT_2PASS_SUPPORTED 
  default:
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
    break;
  }
  post->starting_row = post->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->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 > post->strip_height)
    max_rows = post->strip_height;
  num_rows = 0;
  (*cinfo->upsample->upsample) (cinfo,
		input_buf, in_row_group_ctr, in_row_groups_avail,
		post->buffer, &num_rows, max_rows);
  // Quantize and emit data. 
  (*cinfo->cquantize->color_quantize) (cinfo,
		post->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->post;
  JDIMENSION old_next_row, num_rows;

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

  // Upsample some data (up to a strip height's worth). 
  old_next_row = post->next_row;
  (*cinfo->upsample->upsample) (cinfo,
		input_buf, in_row_group_ctr, in_row_groups_avail,
		post->buffer, &post->next_row, post->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're done. 
  if (post->next_row > old_next_row) {
    num_rows = post->next_row - old_next_row;
    (*cinfo->cquantize->color_quantize) (cinfo, post->buffer + old_next_row,
					 (JSAMPARRAY) NULL, (int) num_rows);
    *out_row_ctr += num_rows;
  }

  // Advance if we filled the strip. 
  if (post->next_row >= post->strip_height) {
    post->starting_row += post->strip_height;
    post->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->post;
  JDIMENSION num_rows, max_rows;

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

  // Determine number of rows to emit. 
  num_rows = post->strip_height - post->next_row; // available in strip 
  max_rows = out_rows_avail - *out_row_ctr; // available in output area 
  if (num_rows > max_rows)
    num_rows = max_rows;
  // We have to check bottom of image here, can't depend on upsampler. 
  max_rows = cinfo->output_height - post->starting_row;
  if (num_rows > max_rows)
    num_rows = max_rows;

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

  // Advance if we filled the strip. 
  post->next_row += num_rows;
  if (post->next_row >= post->strip_height) {
    post->starting_row += post->strip_height;
    post->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->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
				SIZEOF(my_post_controller));
  cinfo->post = (struct jpeg_d_post_controller *) post;
  post->pub.start_pass = start_pass_dpost;
  post->whole_image = NULL;	// flag for no virtual arrays 
  post->buffer = NULL;		// flag for no strip buffer 

  // Create the quantization buffer, if needed 
  if (cinfo->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->strip_height = (JDIMENSION) cinfo->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->whole_image = (*cinfo->mem->request_virt_sarray)
	((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
	 cinfo->output_width * cinfo->out_color_components,
	 (JDIMENSION) jround_up((LONG) cinfo->output_height,
				(LONG) post->strip_height),
	 post->strip_height);
#else
      ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
#endif // QUANT_2PASS_SUPPORTED 
    } else {
      // One-pass color quantization: just make a strip buffer. 
      post->buffer = (*cinfo->mem->alloc_sarray)
	((j_common_ptr) cinfo, JPOOL_IMAGE,
	 cinfo->output_width * cinfo->out_color_components,
	 post->strip_height);
    }
  }
}