jdcoefct.cpp

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#ifdef BLOCK_SMOOTHING_SUPPORTED

/*
 * This code applies interblock smoothing as described by section K.8
 * of the JPEG standard: the first 5 AC coefficients are estimated from
 * the DC values of a DCT block and its 8 neighboring blocks.
 * We apply smoothing only for progressive JPEG decoding, and only if
 * the coefficients it can estimate are not yet known to full precision.
 */

/* Natural-order array positions of the first 5 zigzag-order coefficients */
#define Q01_POS  1
#define Q10_POS  8
#define Q20_POS  16
#define Q11_POS  9
#define Q02_POS  2

/*
 * Determine whether block smoothing is applicable and safe.
 * We also latch the current states of the coef_bits[] entries for the
 * AC coefficients; otherwise, if the input side of the decompressor
 * advances into a new scan, we might think the coefficients are known
 * more accurately than they really are.
 */

LOCAL(boolean)
smoothing_ok (j_decompress_ptr cinfo)
{
	my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
	boolean smoothing_useful = FALSE;
	int ci, coefi;
	jpeg_component_info *compptr;
	JQUANT_TBL * qtable;
	int * coef_bits;
	int * coef_bits_latch;

	if (! cinfo->progressive_mode || cinfo->coef_bits == NULL)
		return FALSE;

	/* Allocate latch area if not already done */
	if (coef->coef_bits_latch == NULL)
		coef->coef_bits_latch = (int *) cinfo->mem->alloc_small(JPOOL_IMAGE,
								cinfo->num_components * (SAVED_COEFS * sizeof(int)));
	
	coef_bits_latch = coef->coef_bits_latch;

	for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++) 
	{
		/* All components' quantization values must already be latched. */
		if ((qtable = compptr->quant_table) == NULL)
			return FALSE;
    
		/* Verify DC & first 5 AC quantizers are nonzero to avoid zero-divide. */
		if (qtable->quantval[0] == 0 ||
			qtable->quantval[Q01_POS] == 0 ||
			qtable->quantval[Q10_POS] == 0 ||
			qtable->quantval[Q20_POS] == 0 ||
			qtable->quantval[Q11_POS] == 0 ||
			qtable->quantval[Q02_POS] == 0)
			return FALSE;
    
		/* DC values must be at least partly known for all components. */
		coef_bits = cinfo->coef_bits[ci];
		if (coef_bits[0] < 0)
			return FALSE;
    
		/* Block smoothing is helpful if some AC coefficients remain inaccurate. */
		for (coefi = 1; coefi <= 5; coefi++) 
		{
			coef_bits_latch[coefi] = coef_bits[coefi];
		
			if (coef_bits[coefi] != 0)
				smoothing_useful = TRUE;
		}
		
		coef_bits_latch += SAVED_COEFS;
	}

	return smoothing_useful;
}


/*
 * Variant of decompress_data for use when doing block smoothing.
 */

int decompress_smooth_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, last_block_column;
	int ci, block_row, block_rows, access_rows;
	JBLOCKARRAY buffer;
	JBLOCKROW buffer_ptr, prev_block_row, next_block_row;
	JSAMPARRAY output_ptr;
	JDIMENSION output_col;
	jpeg_component_info *compptr;
	inverse_DCT_method_ptr inverse_DCT;
	boolean first_row, last_row;
	JBLOCK workspace;
	int *coef_bits;
	JQUANT_TBL *quanttbl;
	long Q00,Q01,Q02,Q10,Q11,Q20, num;
	int DC1,DC2,DC3,DC4,DC5,DC6,DC7,DC8,DC9;
	int Al, pred;

	/* Force some input to be done if we are getting ahead of the input. */
	while (cinfo->input_scan_number <= cinfo->output_scan_number && ! cinfo->inputctl->eoi_reached) 
	{
		if (cinfo->input_scan_number == cinfo->output_scan_number) 
		{
			/* If input is working on current scan, we ordinarily want it to
			* have completed the current row.  But if input scan is DC,
			* we want it to keep one row ahead so that next block row's DC
			* values are up to date.
			*/
			JDIMENSION delta = (cinfo->Ss == 0) ? 1 : 0;
			if (cinfo->input_iMCU_row > cinfo->output_iMCU_row+delta)
				break;
		}
		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;
    
		/* Count non-dummy DCT block rows in this iMCU row. */
		if (cinfo->output_iMCU_row < last_iMCU_row) 
		{
			block_rows = compptr->v_samp_factor;
			access_rows = block_rows * 2; /* this and next iMCU row */
			last_row = FALSE;
		} 
		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;
			
			access_rows = block_rows; /* this iMCU row only */
			last_row = TRUE;
		}
    
		/* Align the virtual buffer for this component. */
		if (cinfo->output_iMCU_row > 0) 
		{
			access_rows += compptr->v_samp_factor; /* prior iMCU row too */
			buffer = cinfo->mem->access_virt_barray
				(coef->whole_image[ci],
				(cinfo->output_iMCU_row - 1) * compptr->v_samp_factor,
				(JDIMENSION) access_rows, FALSE);
      
			buffer += compptr->v_samp_factor;	/* point to current iMCU row */
			first_row = FALSE;
		} 
		else 
		{
			buffer = cinfo->mem->access_virt_barray
					(coef->whole_image[ci],
					(JDIMENSION) 0, (JDIMENSION) access_rows, FALSE);
      
			first_row = TRUE;
		}
    
		/* Fetch component-dependent info */
		coef_bits = coef->coef_bits_latch + (ci * SAVED_COEFS);
		quanttbl = compptr->quant_table;
		Q00 = quanttbl->quantval[0];
		Q01 = quanttbl->quantval[Q01_POS];
		Q10 = quanttbl->quantval[Q10_POS];
		Q20 = quanttbl->quantval[Q20_POS];
		Q11 = quanttbl->quantval[Q11_POS];
		Q02 = quanttbl->quantval[Q02_POS];
    
		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];
			
			if (first_row && block_row == 0)
				prev_block_row = buffer_ptr;
			else
				prev_block_row = buffer[block_row-1];
      
			if (last_row && block_row == block_rows-1)
				next_block_row = buffer_ptr;
			else
				next_block_row = buffer[block_row+1];
      
			/* We fetch the surrounding DC values using a sliding-register approach.
			* Initialize all nine here so as to do the right thing on narrow pics.
			*/
			DC1 = DC2 = DC3 = (int) prev_block_row[0][0];
			DC4 = DC5 = DC6 = (int) buffer_ptr[0][0];
			DC7 = DC8 = DC9 = (int) next_block_row[0][0];
			output_col = 0;
			last_block_column = compptr->width_in_blocks - 1;
      
			for (block_num = 0; block_num <= last_block_column; block_num++) 
			{
				/* Fetch current DCT block into workspace so we can modify it. */
				jcopy_block_row(buffer_ptr, (JBLOCKROW) workspace, (JDIMENSION) 1);
				
				/* Update DC values */
				if (block_num < last_block_column) 
				{
					DC3 = (int) prev_block_row[1][0];
					DC6 = (int) buffer_ptr[1][0];
					DC9 = (int) next_block_row[1][0];
				}
	
				/* Compute coefficient estimates per K.8.
				* An estimate is applied only if coefficient is still zero,
				* and is not known to be fully accurate.
				*/
				/* AC01 */
				if ((Al=coef_bits[1]) != 0 && workspace[1] == 0) 
				{
					num = 36 * Q00 * (DC4 - DC6);
					if (num >= 0) 
					{
						pred = (int) (((Q01<<7) + num) / (Q01<<8));
						if (Al > 0 && pred >= (1<<Al))
							pred = (1<<Al)-1;
					} 
					else 
					{
						pred = (int) (((Q01<<7) - num) / (Q01<<8));
						if (Al > 0 && pred >= (1<<Al))
							pred = (1<<Al)-1;
						pred = -pred;
					}
	  
					workspace[1] = (JCOEF) pred;
				}
				
				/* AC10 */
				if ((Al=coef_bits[2]) != 0 && workspace[8] == 0) 
				{
					num = 36 * Q00 * (DC2 - DC8);
					if (num >= 0) 
					{
						pred = (int) (((Q10<<7) + num) / (Q10<<8));
						
						if (Al > 0 && pred >= (1<<Al))
							pred = (1<<Al)-1;
					} 
					else 
					{
						pred = (int) (((Q10<<7) - num) / (Q10<<8));
						if (Al > 0 && pred >= (1<<Al))
							pred = (1<<Al)-1;
						pred = -pred;
					}
					workspace[8] = (JCOEF) pred;
				}
	
				/* AC20 */
				if ((Al=coef_bits[3]) != 0 && workspace[16] == 0) 
				{
					num = 9 * Q00 * (DC2 + DC8 - 2*DC5);
					if (num >= 0) 
					{
						pred = (int) (((Q20<<7) + num) / (Q20<<8));
						if (Al > 0 && pred >= (1<<Al))
							pred = (1<<Al)-1;
					} 
					else 
					{
						pred = (int) (((Q20<<7) - num) / (Q20<<8));
						if (Al > 0 && pred >= (1<<Al))
							pred = (1<<Al)-1;
						pred = -pred;
					}
	  
					workspace[16] = (JCOEF) pred;
				}
	
				/* AC11 */
				if ((Al=coef_bits[4]) != 0 && workspace[9] == 0) 
				{
					num = 5 * Q00 * (DC1 - DC3 - DC7 + DC9);
					if (num >= 0) 
					{
						pred = (int) (((Q11<<7) + num) / (Q11<<8));
						if (Al > 0 && pred >= (1<<Al))
							pred = (1<<Al)-1;
					} 
					else 
					{
						pred = (int) (((Q11<<7) - num) / (Q11<<8));
						if (Al > 0 && pred >= (1<<Al))
							pred = (1<<Al)-1;
						pred = -pred;
					}
					workspace[9] = (JCOEF) pred;
				}
	
				/* AC02 */
				if ((Al=coef_bits[5]) != 0 && workspace[2] == 0) 
				{
					num = 9 * Q00 * (DC4 + DC6 - 2*DC5);
					if (num >= 0) 
					{
						pred = (int) (((Q02<<7) + num) / (Q02<<8));
						
						if (Al > 0 && pred >= (1<<Al))
							pred = (1<<Al)-1;
					} 
					else 
					{
						pred = (int) (((Q02<<7) - num) / (Q02<<8));
						
						if (Al > 0 && pred >= (1<<Al))
							pred = (1<<Al)-1;
						pred = -pred;
					}
				
					workspace[2] = (JCOEF) pred;
				}
	
				/* OK, do the IDCT */
				(*inverse_DCT) (cinfo, compptr, (JCOEFPTR) workspace, output_ptr, output_col);
	
				/* Advance for next column */
				DC1 = DC2; DC2 = DC3;
				DC4 = DC5; DC5 = DC6;
				DC7 = DC8; DC8 = DC9;
				buffer_ptr++, prev_block_row++, next_block_row++;
				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 /* BLOCK_SMOOTHING_SUPPORTED */


/*
 * Initialize coefficient buffer controller.
 */

GLOBAL(void)
jinit_d_coef_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
{
	my_coef_ptr coef;

	coef = (my_coef_ptr) cinfo->mem->alloc_small (JPOOL_IMAGE, sizeof(my_coef_controller));
  
	cinfo->coef = (struct jpeg_d_coef_controller *) coef;
	coef->pub.start_input_pass = start_input_pass;
	coef->pub.start_output_pass = start_output_pass;

#ifdef BLOCK_SMOOTHING_SUPPORTED
	coef->coef_bits_latch = NULL;
#endif

	/* Create the coefficient buffer. */
	if (need_full_buffer) 
	{
#ifdef D_MULTISCAN_FILES_SUPPORTED
		/* Allocate a full-image virtual array for each component, */
		/* padded to a multiple of samp_factor DCT blocks in each direction. */
		/* Note we ask for a pre-zeroed array. */
		int ci, access_rows;
		jpeg_component_info *compptr;

		for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++) 
		{
			access_rows = compptr->v_samp_factor;
#ifdef BLOCK_SMOOTHING_SUPPORTED
			/* If block smoothing could be used, need a bigger window */
			if (cinfo->progressive_mode)
				access_rows *= 3;
#endif
			coef->whole_image[ci] = cinfo->mem->request_virt_barray
				(JPOOL_IMAGE, TRUE,
				(JDIMENSION) jround_up((long) compptr->width_in_blocks,  (long) compptr->h_samp_factor),
				(JDIMENSION) jround_up((long) compptr->height_in_blocks, (long) compptr->v_samp_factor),
				(JDIMENSION) access_rows);
		}
    
		coef->pub.consume_data = consume_data;
		coef->pub.decompress_data = decompress_data;
		coef->pub.coef_arrays = coef->whole_image; /* link to virtual arrays */
#else
		ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif
	} 
	else 
	{
		/* We only need a single-MCU buffer. */
		JBLOCKROW buffer = (JBLOCKROW) cinfo->mem->alloc_large(JPOOL_IMAGE, D_MAX_BLOCKS_IN_MCU * sizeof(JBLOCK));
    
		for (int i = 0; i < D_MAX_BLOCKS_IN_MCU; i++) 
		{
			coef->MCU_buffer[i] = buffer + i;
		}
    
		coef->pub.consume_data = dummy_consume_data;
		coef->pub.decompress_data = decompress_onepass;
		coef->pub.coef_arrays = NULL; /* flag for no virtual arrays */
	}
}