jdcoefct.cpp

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//-------------------------------------------------------------------------//
//          Windows Graphics Programming: Win32 GDI and DirectDraw         //
//                        ISBN  0-13-086985-6                              //
//                                                                         //
//  Modified by: Yuan, Feng                             www.fengyuan.com   //
//  Changes    : C++, exception, in-memory source, BGR byte order          //
//  Version    : 1.00.000, May 31, 2000                                    //
//-------------------------------------------------------------------------//

/*
 * jdcoefct.c
 *
 * Copyright (C) 1994-1997, 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 coefficient buffer controller for decompression.
 * This controller is the top level of the JPEG decompressor proper.
 * The coefficient buffer lies between entropy decoding and inverse-DCT steps.
 *
 * In buffered-image mode, this controller is the interface between
 * input-oriented processing and output-oriented processing.
 * Also, the input side (only) is used when reading a file for transcoding.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"

/* Block smoothing is only applicable for progressive JPEG, so: */
#ifndef D_PROGRESSIVE_SUPPORTED
#undef BLOCK_SMOOTHING_SUPPORTED
#endif

/* Private buffer controller object */

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

  /* These variables keep track of the current location of the input side. */
  /* cinfo->input_iMCU_row is also used for this. */
  JDIMENSION MCU_ctr;		/* counts MCUs processed in current row */
  int MCU_vert_offset;		/* counts MCU rows within iMCU row */
  int MCU_rows_per_iMCU_row;	/* number of such rows needed */

  /* The output side's location is represented by cinfo->output_iMCU_row. */

  /* In single-pass modes, it's sufficient to buffer just one MCU.
   * We allocate a workspace of D_MAX_BLOCKS_IN_MCU coefficient blocks,
   * and let the entropy decoder write into that workspace each time.
   * (On 80x86, the workspace is FAR even though it's not really very big;
   * this is to keep the module interfaces unchanged when a large coefficient
   * buffer is necessary.)
   * In multi-pass modes, this array points to the current MCU's blocks
   * within the virtual arrays; it is used only by the input side.
   */
  JBLOCKROW MCU_buffer[D_MAX_BLOCKS_IN_MCU];

#ifdef D_MULTISCAN_FILES_SUPPORTED
  /* In multi-pass modes, we need a virtual block array for each component. */
  jvirt_barray_ptr whole_image[MAX_COMPONENTS];
#endif

#ifdef BLOCK_SMOOTHING_SUPPORTED
  /* When doing block smoothing, we latch coefficient Al values here */
  int * coef_bits_latch;
#define SAVED_COEFS  6		/* we save coef_bits[0..5] */
#endif
} my_coef_controller;

typedef my_coef_controller * my_coef_ptr;

/* Forward declarations */
int decompress_onepass
	(j_decompress_ptr cinfo, JSAMPIMAGE output_buf);

#ifdef D_MULTISCAN_FILES_SUPPORTED
int decompress_data(j_decompress_ptr cinfo, JSAMPIMAGE output_buf);
#endif

#ifdef BLOCK_SMOOTHING_SUPPORTED
LOCAL(boolean) smoothing_ok (j_decompress_ptr cinfo);
int decompress_smooth_data(j_decompress_ptr cinfo, JSAMPIMAGE output_buf);
#endif


LOCAL(void) start_iMCU_row (j_decompress_ptr cinfo)
/* Reset within-iMCU-row counters for a new row (input side) */
{
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

	/* In an interleaved scan, an MCU row is the same as an iMCU row.
	* In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
	* But at the bottom of the image, process only what's left.
	*/
	if (cinfo->comps_in_scan > 1) 
	{
		coef->MCU_rows_per_iMCU_row = 1;
	} 
	else 
	{
		if (cinfo->input_iMCU_row < (cinfo->total_iMCU_rows-1))
			coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
		else
			coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
	}

	coef->MCU_ctr = 0;
	coef->MCU_vert_offset = 0;
}


/*
 * Initialize for an input processing pass.
 */

void start_input_pass (j_decompress_ptr cinfo)
{
	cinfo->input_iMCU_row = 0;
	start_iMCU_row(cinfo);
}


/*
 * Initialize for an output processing pass.
 */

void start_output_pass (j_decompress_ptr cinfo)
{
#ifdef BLOCK_SMOOTHING_SUPPORTED
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;

	/* If multipass, check to see whether to use block smoothing on this pass */
	if (coef->pub.coef_arrays != NULL) 
	{
		if (cinfo->do_block_smoothing && smoothing_ok(cinfo))
			coef->pub.decompress_data = decompress_smooth_data;
		else
			coef->pub.decompress_data = decompress_data;
	}
#endif
	
	cinfo->output_iMCU_row = 0;
}


/*
 * Decompress and return some data in the single-pass case.
 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
 * Input and output must run in lockstep since we have only a one-MCU buffer.
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 *
 * NB: output_buf contains a plane for each component in image,
 * which we index according to the component's SOF position.
 */

int decompress_onepass (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
{
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
	JDIMENSION MCU_col_num;	/* index of current MCU within row */
	JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
	JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
	int blkn, ci, xindex, yindex, yoffset, useful_width;
	JSAMPARRAY output_ptr;
	JDIMENSION start_col, output_col;
	jpeg_component_info *compptr;
	inverse_DCT_method_ptr inverse_DCT;

	/* Loop to process as much as one whole iMCU row */
	for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row; yoffset++) 
	{
		for (MCU_col_num = coef->MCU_ctr; MCU_col_num <= last_MCU_col; MCU_col_num++) 
		{
			/* Try to fetch an MCU.  Entropy decoder expects buffer to be zeroed. */
			jzero_far((void *) coef->MCU_buffer[0],	(size_t) (cinfo->blocks_in_MCU * sizeof(JBLOCK)));

			if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) 
			{
				/* Suspension forced; update state counters and exit */
				coef->MCU_vert_offset = yoffset;
				coef->MCU_ctr = MCU_col_num;
				return JPEG_SUSPENDED;
			}
      
			/* Determine where data should go in output_buf and do the IDCT thing.
			* We skip dummy blocks at the right and bottom edges (but blkn gets
			* incremented past them!).  Note the inner loop relies on having
			* allocated the MCU_buffer[] blocks sequentially.
			*/
			blkn = 0;			/* index of current DCT block within MCU */
			for (ci = 0; ci < cinfo->comps_in_scan; ci++) 
			{
				compptr = cinfo->cur_comp_info[ci];
				/* Don't bother to IDCT an uninteresting component. */
				if (! compptr->component_needed) 
				{
					blkn += compptr->MCU_blocks;
					continue;
				}
	
				inverse_DCT = cinfo->idct->inverse_DCT[compptr->component_index];
				useful_width = (MCU_col_num < last_MCU_col) ? compptr->MCU_width : compptr->last_col_width;
	
				output_ptr = output_buf[compptr->component_index] +
				  yoffset * compptr->DCT_scaled_size;
	
				start_col = MCU_col_num * compptr->MCU_sample_width;
				for (yindex = 0; yindex < compptr->MCU_height; yindex++) 
				{
					if (cinfo->input_iMCU_row < last_iMCU_row ||
						yoffset+yindex < compptr->last_row_height) 
					{
						output_col = start_col;
						
						for (xindex = 0; xindex < useful_width; xindex++) 
						{
							(*inverse_DCT) (cinfo, compptr, (JCOEFPTR) coef->MCU_buffer[blkn+xindex],
								output_ptr, output_col);
							output_col += compptr->DCT_scaled_size;
						}
					}
	  
					blkn += compptr->MCU_width;
					output_ptr += compptr->DCT_scaled_size;
				}
			}
		}
    
		/* Completed an MCU row, but perhaps not an iMCU row */
		coef->MCU_ctr = 0;
	}
  
	/* Completed the iMCU row, advance counters for next one */
	cinfo->output_iMCU_row++;
	
	if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) 
	{
		start_iMCU_row(cinfo);
		return JPEG_ROW_COMPLETED;
	}
  
	/* Completed the scan */
	(*cinfo->inputctl->finish_input_pass) (cinfo);
	
	return JPEG_SCAN_COMPLETED;
}


/*
 * Dummy consume-input routine for single-pass operation.
 */

int dummy_consume_data (j_decompress_ptr cinfo)
{
	return JPEG_SUSPENDED;	/* Always indicate nothing was done */
}


#ifdef D_MULTISCAN_FILES_SUPPORTED

/*
 * Consume input data and store it in the full-image coefficient buffer.
 * We read as much as one fully interleaved MCU row ("iMCU" row) per call,
 * ie, v_samp_factor block rows for each component in the scan.
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 */

int consume_data (j_decompress_ptr cinfo)
{
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
	JDIMENSION MCU_col_num;	/* index of current MCU within row */
	int blkn, ci, xindex, yindex, yoffset;
	JDIMENSION start_col;
	JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
	JBLOCKROW buffer_ptr;
	jpeg_component_info *compptr;

	/* Align the virtual buffers for the components used in this scan. */
	for (ci = 0; ci < cinfo->comps_in_scan; ci++) 
	{
		compptr = cinfo->cur_comp_info[ci];
		buffer[ci] = cinfo->mem->access_virt_barray
			(coef->whole_image[compptr->component_index],
			cinfo->input_iMCU_row * compptr->v_samp_factor,
			(JDIMENSION) compptr->v_samp_factor, TRUE);
    
		/* Note: entropy decoder expects buffer to be zeroed,
		* but this is handled automatically by the memory manager
		* because we requested a pre-zeroed array.
		*/
	}

	/* Loop to process one whole iMCU row */
	for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row; yoffset++) 
	{
		for (MCU_col_num = coef->MCU_ctr; MCU_col_num < cinfo->MCUs_per_row; MCU_col_num++) 
		{
			/* Construct list of pointers to DCT blocks belonging to this MCU */
			blkn = 0;			/* index of current DCT block within MCU */
      
			for (ci = 0; ci < cinfo->comps_in_scan; ci++) 
			{
				compptr = cinfo->cur_comp_info[ci];
				start_col = MCU_col_num * compptr->MCU_width;
				for (yindex = 0; yindex < compptr->MCU_height; yindex++) 
				{
					buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
					for (xindex = 0; xindex < compptr->MCU_width; xindex++) 
					{
						coef->MCU_buffer[blkn++] = buffer_ptr++;
					}
				}
			}
      
			/* Try to fetch the MCU. */
			if (! (*cinfo->entropy->decode_mcu) (cinfo, coef->MCU_buffer)) 
			{
				/* Suspension forced; update state counters and exit */
				coef->MCU_vert_offset = yoffset;
				coef->MCU_ctr = MCU_col_num;
				return JPEG_SUSPENDED;
			}
		}
    
		/* Completed an MCU row, but perhaps not an iMCU row */
		coef->MCU_ctr = 0;
	}
  
	/* Completed the iMCU row, advance counters for next one */
	if (++(cinfo->input_iMCU_row) < cinfo->total_iMCU_rows) 
	{
		start_iMCU_row(cinfo);
		return JPEG_ROW_COMPLETED;
	}
  
	/* Completed the scan */
	(*cinfo->inputctl->finish_input_pass) (cinfo);
	return JPEG_SCAN_COMPLETED;
}


/*
 * Decompress and return some data in the multi-pass case.
 * Always attempts to emit one fully interleaved MCU row ("iMCU" row).
 * Return value is JPEG_ROW_COMPLETED, JPEG_SCAN_COMPLETED, or JPEG_SUSPENDED.
 *
 * NB: output_buf contains a plane for each component in image.
 */

int decompress_data (j_decompress_ptr cinfo, JSAMPIMAGE output_buf)
{
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
	JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
	JDIMENSION block_num;
	int ci, block_row, block_rows;
	JBLOCKARRAY buffer;
	JBLOCKROW buffer_ptr;
	JSAMPARRAY output_ptr;
	JDIMENSION output_col;
	jpeg_component_info *compptr;
	inverse_DCT_method_ptr inverse_DCT;

	/* Force some input to be done if we are getting ahead of the input. */
	while (cinfo->input_scan_number < cinfo->output_scan_number ||
		 (cinfo->input_scan_number == cinfo->output_scan_number &&
		  cinfo->input_iMCU_row <= cinfo->output_iMCU_row)) 
	{
		if ((*cinfo->inputctl->consume_input)(cinfo) == JPEG_SUSPENDED)
			return JPEG_SUSPENDED;
	}

	/* OK, output from the virtual arrays. */
	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++) 
	{
		/* Don't bother to IDCT an uninteresting component. */
		if (! compptr->component_needed)
			continue;
    
		/* Align the virtual buffer for this component. */
		buffer = cinfo->mem->access_virt_barray(coef->whole_image[ci],
			cinfo->output_iMCU_row * compptr->v_samp_factor,
			(JDIMENSION) compptr->v_samp_factor, FALSE);
    
		/* Count non-dummy DCT block rows in this iMCU row. */
		if (cinfo->output_iMCU_row < last_iMCU_row)
			block_rows = compptr->v_samp_factor;
		else 
		{
			/* NB: can't use last_row_height here; it is input-side-dependent! */
			block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
			
			if (block_rows == 0) 
				block_rows = compptr->v_samp_factor;
		}
    
		inverse_DCT = cinfo->idct->inverse_DCT[ci];
		output_ptr = output_buf[ci];
	
		/* Loop over all DCT blocks to be processed. */
		for (block_row = 0; block_row < block_rows; block_row++) 
		{
			buffer_ptr = buffer[block_row];
			output_col = 0;
      
			for (block_num = 0; block_num < compptr->width_in_blocks; block_num++) 
			{
				(*inverse_DCT) (cinfo, compptr, (JCOEFPTR) buffer_ptr, output_ptr, output_col);
	
				buffer_ptr++;
				output_col += compptr->DCT_scaled_size;
			}
			output_ptr += compptr->DCT_scaled_size;
		}
	}

	if (++(cinfo->output_iMCU_row) < cinfo->total_iMCU_rows)
		return JPEG_ROW_COMPLETED;
  
	return JPEG_SCAN_COMPLETED;
}

#endif /* D_MULTISCAN_FILES_SUPPORTED */