www.pudn.com > imgport.rar > jdpostct.c, change:2008-11-05,size:10013b


/* 
 * jdpostct.c 
 * 
 * Copyright (C) 1994-1996, 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); 
    } 
  } 
}