The Tor Browser: media/libjpeg/jdcoefct.c@6474c204b198 (annotated)

media/libjpeg/jdcoefct.c@6474c204b198 (annotated)

media/libjpeg/jdcoefct.c

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /*
  * jdcoefct.c
  *
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1994-1997, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright (C) 2010, D. R. Commander.
  * 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"
 #include "jpegcomp.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];
   /* Temporary workspace for one MCU */
   JCOEF * workspace;
 #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 */
 METHODDEF(int) decompress_onepass
 	JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
 #ifdef D_MULTISCAN_FILES_SUPPORTED
 METHODDEF(int) decompress_data
 	JPP((j_decompress_ptr cinfo, JSAMPIMAGE output_buf));
 #endif
 #ifdef BLOCK_SMOOTHING_SUPPORTED
 LOCAL(boolean) smoothing_ok JPP((j_decompress_ptr cinfo));
 METHODDEF(int) decompress_smooth_data
 	JPP((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.
  */
 METHODDEF(void)
 start_input_pass (j_decompress_ptr cinfo)
 {
   cinfo->input_iMCU_row = 0;
   start_iMCU_row(cinfo);
 }
 /*
  * Initialize for an output processing pass.
  */
 METHODDEF(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.
  */
 METHODDEF(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 FAR *) 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.
  */
 METHODDEF(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.
  */
 METHODDEF(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)
       ((j_common_ptr) cinfo, 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.
  */
 METHODDEF(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)
       ((j_common_ptr) cinfo, 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 */
 #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) ((j_common_ptr) cinfo, 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.
  */
 METHODDEF(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;
   JCOEF * workspace;
   int *coef_bits;
   JQUANT_TBL *quanttbl;
   INT32 Q00,Q01,Q02,Q10,Q11,Q20, num;
   int DC1,DC2,DC3,DC4,DC5,DC6,DC7,DC8,DC9;
   int Al, pred;
   /* Keep a local variable to avoid looking it up more than once */
   workspace = coef->workspace;
   /* 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)
 	((j_common_ptr) cinfo, 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)
 	((j_common_ptr) cinfo, 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) ((j_common_ptr) cinfo, 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)
 	((j_common_ptr) cinfo, 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;
     int i;
     buffer = (JBLOCKROW)
       (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 				  D_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
     for (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 */
   }
   /* Allocate the workspace buffer */
   coef->workspace = (JCOEF *)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                 SIZEOF(JCOEF) * DCTSIZE2);
 }

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media/libjpeg/jdcoefct.c@6474c204b198 (annotated)

media/libjpeg/jdcoefct.c