michael@0: /*
michael@0:  * jccoefct.c
michael@0:  *
michael@0:  * Copyright (C) 1994-1997, Thomas G. Lane.
michael@0:  * This file is part of the Independent JPEG Group's software.
michael@0:  * For conditions of distribution and use, see the accompanying README file.
michael@0:  *
michael@0:  * This file contains the coefficient buffer controller for compression.
michael@0:  * This controller is the top level of the JPEG compressor proper.
michael@0:  * The coefficient buffer lies between forward-DCT and entropy encoding steps.
michael@0:  */
michael@0: 
michael@0: #define JPEG_INTERNALS
michael@0: #include "jinclude.h"
michael@0: #include "jpeglib.h"
michael@0: 
michael@0: 
michael@0: /* We use a full-image coefficient buffer when doing Huffman optimization,
michael@0:  * and also for writing multiple-scan JPEG files.  In all cases, the DCT
michael@0:  * step is run during the first pass, and subsequent passes need only read
michael@0:  * the buffered coefficients.
michael@0:  */
michael@0: #ifdef ENTROPY_OPT_SUPPORTED
michael@0: #define FULL_COEF_BUFFER_SUPPORTED
michael@0: #else
michael@0: #ifdef C_MULTISCAN_FILES_SUPPORTED
michael@0: #define FULL_COEF_BUFFER_SUPPORTED
michael@0: #endif
michael@0: #endif
michael@0: 
michael@0: 
michael@0: /* Private buffer controller object */
michael@0: 
michael@0: typedef struct {
michael@0:   struct jpeg_c_coef_controller pub; /* public fields */
michael@0: 
michael@0:   JDIMENSION iMCU_row_num;	/* iMCU row # within image */
michael@0:   JDIMENSION mcu_ctr;		/* counts MCUs processed in current row */
michael@0:   int MCU_vert_offset;		/* counts MCU rows within iMCU row */
michael@0:   int MCU_rows_per_iMCU_row;	/* number of such rows needed */
michael@0: 
michael@0:   /* For single-pass compression, it's sufficient to buffer just one MCU
michael@0:    * (although this may prove a bit slow in practice).  We allocate a
michael@0:    * workspace of C_MAX_BLOCKS_IN_MCU coefficient blocks, and reuse it for each
michael@0:    * MCU constructed and sent.  (On 80x86, the workspace is FAR even though
michael@0:    * it's not really very big; this is to keep the module interfaces unchanged
michael@0:    * when a large coefficient buffer is necessary.)
michael@0:    * In multi-pass modes, this array points to the current MCU's blocks
michael@0:    * within the virtual arrays.
michael@0:    */
michael@0:   JBLOCKROW MCU_buffer[C_MAX_BLOCKS_IN_MCU];
michael@0: 
michael@0:   /* In multi-pass modes, we need a virtual block array for each component. */
michael@0:   jvirt_barray_ptr whole_image[MAX_COMPONENTS];
michael@0: } my_coef_controller;
michael@0: 
michael@0: typedef my_coef_controller * my_coef_ptr;
michael@0: 
michael@0: 
michael@0: /* Forward declarations */
michael@0: METHODDEF(boolean) compress_data
michael@0:     JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
michael@0: #ifdef FULL_COEF_BUFFER_SUPPORTED
michael@0: METHODDEF(boolean) compress_first_pass
michael@0:     JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
michael@0: METHODDEF(boolean) compress_output
michael@0:     JPP((j_compress_ptr cinfo, JSAMPIMAGE input_buf));
michael@0: #endif
michael@0: 
michael@0: 
michael@0: LOCAL(void)
michael@0: start_iMCU_row (j_compress_ptr cinfo)
michael@0: /* Reset within-iMCU-row counters for a new row */
michael@0: {
michael@0:   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
michael@0: 
michael@0:   /* In an interleaved scan, an MCU row is the same as an iMCU row.
michael@0:    * In a noninterleaved scan, an iMCU row has v_samp_factor MCU rows.
michael@0:    * But at the bottom of the image, process only what's left.
michael@0:    */
michael@0:   if (cinfo->comps_in_scan > 1) {
michael@0:     coef->MCU_rows_per_iMCU_row = 1;
michael@0:   } else {
michael@0:     if (coef->iMCU_row_num < (cinfo->total_iMCU_rows-1))
michael@0:       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->v_samp_factor;
michael@0:     else
michael@0:       coef->MCU_rows_per_iMCU_row = cinfo->cur_comp_info[0]->last_row_height;
michael@0:   }
michael@0: 
michael@0:   coef->mcu_ctr = 0;
michael@0:   coef->MCU_vert_offset = 0;
michael@0: }
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * Initialize for a processing pass.
michael@0:  */
michael@0: 
michael@0: METHODDEF(void)
michael@0: start_pass_coef (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
michael@0: {
michael@0:   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
michael@0: 
michael@0:   coef->iMCU_row_num = 0;
michael@0:   start_iMCU_row(cinfo);
michael@0: 
michael@0:   switch (pass_mode) {
michael@0:   case JBUF_PASS_THRU:
michael@0:     if (coef->whole_image[0] != NULL)
michael@0:       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
michael@0:     coef->pub.compress_data = compress_data;
michael@0:     break;
michael@0: #ifdef FULL_COEF_BUFFER_SUPPORTED
michael@0:   case JBUF_SAVE_AND_PASS:
michael@0:     if (coef->whole_image[0] == NULL)
michael@0:       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
michael@0:     coef->pub.compress_data = compress_first_pass;
michael@0:     break;
michael@0:   case JBUF_CRANK_DEST:
michael@0:     if (coef->whole_image[0] == NULL)
michael@0:       ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
michael@0:     coef->pub.compress_data = compress_output;
michael@0:     break;
michael@0: #endif
michael@0:   default:
michael@0:     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
michael@0:     break;
michael@0:   }
michael@0: }
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * Process some data in the single-pass case.
michael@0:  * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
michael@0:  * per call, ie, v_samp_factor block rows for each component in the image.
michael@0:  * Returns TRUE if the iMCU row is completed, FALSE if suspended.
michael@0:  *
michael@0:  * NB: input_buf contains a plane for each component in image,
michael@0:  * which we index according to the component's SOF position.
michael@0:  */
michael@0: 
michael@0: METHODDEF(boolean)
michael@0: compress_data (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
michael@0: {
michael@0:   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
michael@0:   JDIMENSION MCU_col_num;	/* index of current MCU within row */
michael@0:   JDIMENSION last_MCU_col = cinfo->MCUs_per_row - 1;
michael@0:   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
michael@0:   int blkn, bi, ci, yindex, yoffset, blockcnt;
michael@0:   JDIMENSION ypos, xpos;
michael@0:   jpeg_component_info *compptr;
michael@0: 
michael@0:   /* Loop to write as much as one whole iMCU row */
michael@0:   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
michael@0:        yoffset++) {
michael@0:     for (MCU_col_num = coef->mcu_ctr; MCU_col_num <= last_MCU_col;
michael@0: 	 MCU_col_num++) {
michael@0:       /* Determine where data comes from in input_buf and do the DCT thing.
michael@0:        * Each call on forward_DCT processes a horizontal row of DCT blocks
michael@0:        * as wide as an MCU; we rely on having allocated the MCU_buffer[] blocks
michael@0:        * sequentially.  Dummy blocks at the right or bottom edge are filled in
michael@0:        * specially.  The data in them does not matter for image reconstruction,
michael@0:        * so we fill them with values that will encode to the smallest amount of
michael@0:        * data, viz: all zeroes in the AC entries, DC entries equal to previous
michael@0:        * block's DC value.  (Thanks to Thomas Kinsman for this idea.)
michael@0:        */
michael@0:       blkn = 0;
michael@0:       for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
michael@0: 	compptr = cinfo->cur_comp_info[ci];
michael@0: 	blockcnt = (MCU_col_num < last_MCU_col) ? compptr->MCU_width
michael@0: 						: compptr->last_col_width;
michael@0: 	xpos = MCU_col_num * compptr->MCU_sample_width;
michael@0: 	ypos = yoffset * DCTSIZE; /* ypos == (yoffset+yindex) * DCTSIZE */
michael@0: 	for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
michael@0: 	  if (coef->iMCU_row_num < last_iMCU_row ||
michael@0: 	      yoffset+yindex < compptr->last_row_height) {
michael@0: 	    (*cinfo->fdct->forward_DCT) (cinfo, compptr,
michael@0: 					 input_buf[compptr->component_index],
michael@0: 					 coef->MCU_buffer[blkn],
michael@0: 					 ypos, xpos, (JDIMENSION) blockcnt);
michael@0: 	    if (blockcnt < compptr->MCU_width) {
michael@0: 	      /* Create some dummy blocks at the right edge of the image. */
michael@0: 	      jzero_far((void FAR *) coef->MCU_buffer[blkn + blockcnt],
michael@0: 			(compptr->MCU_width - blockcnt) * SIZEOF(JBLOCK));
michael@0: 	      for (bi = blockcnt; bi < compptr->MCU_width; bi++) {
michael@0: 		coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn+bi-1][0][0];
michael@0: 	      }
michael@0: 	    }
michael@0: 	  } else {
michael@0: 	    /* Create a row of dummy blocks at the bottom of the image. */
michael@0: 	    jzero_far((void FAR *) coef->MCU_buffer[blkn],
michael@0: 		      compptr->MCU_width * SIZEOF(JBLOCK));
michael@0: 	    for (bi = 0; bi < compptr->MCU_width; bi++) {
michael@0: 	      coef->MCU_buffer[blkn+bi][0][0] = coef->MCU_buffer[blkn-1][0][0];
michael@0: 	    }
michael@0: 	  }
michael@0: 	  blkn += compptr->MCU_width;
michael@0: 	  ypos += DCTSIZE;
michael@0: 	}
michael@0:       }
michael@0:       /* Try to write the MCU.  In event of a suspension failure, we will
michael@0:        * re-DCT the MCU on restart (a bit inefficient, could be fixed...)
michael@0:        */
michael@0:       if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
michael@0: 	/* Suspension forced; update state counters and exit */
michael@0: 	coef->MCU_vert_offset = yoffset;
michael@0: 	coef->mcu_ctr = MCU_col_num;
michael@0: 	return FALSE;
michael@0:       }
michael@0:     }
michael@0:     /* Completed an MCU row, but perhaps not an iMCU row */
michael@0:     coef->mcu_ctr = 0;
michael@0:   }
michael@0:   /* Completed the iMCU row, advance counters for next one */
michael@0:   coef->iMCU_row_num++;
michael@0:   start_iMCU_row(cinfo);
michael@0:   return TRUE;
michael@0: }
michael@0: 
michael@0: 
michael@0: #ifdef FULL_COEF_BUFFER_SUPPORTED
michael@0: 
michael@0: /*
michael@0:  * Process some data in the first pass of a multi-pass case.
michael@0:  * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
michael@0:  * per call, ie, v_samp_factor block rows for each component in the image.
michael@0:  * This amount of data is read from the source buffer, DCT'd and quantized,
michael@0:  * and saved into the virtual arrays.  We also generate suitable dummy blocks
michael@0:  * as needed at the right and lower edges.  (The dummy blocks are constructed
michael@0:  * in the virtual arrays, which have been padded appropriately.)  This makes
michael@0:  * it possible for subsequent passes not to worry about real vs. dummy blocks.
michael@0:  *
michael@0:  * We must also emit the data to the entropy encoder.  This is conveniently
michael@0:  * done by calling compress_output() after we've loaded the current strip
michael@0:  * of the virtual arrays.
michael@0:  *
michael@0:  * NB: input_buf contains a plane for each component in image.  All
michael@0:  * components are DCT'd and loaded into the virtual arrays in this pass.
michael@0:  * However, it may be that only a subset of the components are emitted to
michael@0:  * the entropy encoder during this first pass; be careful about looking
michael@0:  * at the scan-dependent variables (MCU dimensions, etc).
michael@0:  */
michael@0: 
michael@0: METHODDEF(boolean)
michael@0: compress_first_pass (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
michael@0: {
michael@0:   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
michael@0:   JDIMENSION last_iMCU_row = cinfo->total_iMCU_rows - 1;
michael@0:   JDIMENSION blocks_across, MCUs_across, MCUindex;
michael@0:   int bi, ci, h_samp_factor, block_row, block_rows, ndummy;
michael@0:   JCOEF lastDC;
michael@0:   jpeg_component_info *compptr;
michael@0:   JBLOCKARRAY buffer;
michael@0:   JBLOCKROW thisblockrow, lastblockrow;
michael@0: 
michael@0:   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
michael@0:        ci++, compptr++) {
michael@0:     /* Align the virtual buffer for this component. */
michael@0:     buffer = (*cinfo->mem->access_virt_barray)
michael@0:       ((j_common_ptr) cinfo, coef->whole_image[ci],
michael@0:        coef->iMCU_row_num * compptr->v_samp_factor,
michael@0:        (JDIMENSION) compptr->v_samp_factor, TRUE);
michael@0:     /* Count non-dummy DCT block rows in this iMCU row. */
michael@0:     if (coef->iMCU_row_num < last_iMCU_row)
michael@0:       block_rows = compptr->v_samp_factor;
michael@0:     else {
michael@0:       /* NB: can't use last_row_height here, since may not be set! */
michael@0:       block_rows = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
michael@0:       if (block_rows == 0) block_rows = compptr->v_samp_factor;
michael@0:     }
michael@0:     blocks_across = compptr->width_in_blocks;
michael@0:     h_samp_factor = compptr->h_samp_factor;
michael@0:     /* Count number of dummy blocks to be added at the right margin. */
michael@0:     ndummy = (int) (blocks_across % h_samp_factor);
michael@0:     if (ndummy > 0)
michael@0:       ndummy = h_samp_factor - ndummy;
michael@0:     /* Perform DCT for all non-dummy blocks in this iMCU row.  Each call
michael@0:      * on forward_DCT processes a complete horizontal row of DCT blocks.
michael@0:      */
michael@0:     for (block_row = 0; block_row < block_rows; block_row++) {
michael@0:       thisblockrow = buffer[block_row];
michael@0:       (*cinfo->fdct->forward_DCT) (cinfo, compptr,
michael@0: 				   input_buf[ci], thisblockrow,
michael@0: 				   (JDIMENSION) (block_row * DCTSIZE),
michael@0: 				   (JDIMENSION) 0, blocks_across);
michael@0:       if (ndummy > 0) {
michael@0: 	/* Create dummy blocks at the right edge of the image. */
michael@0: 	thisblockrow += blocks_across; /* => first dummy block */
michael@0: 	jzero_far((void FAR *) thisblockrow, ndummy * SIZEOF(JBLOCK));
michael@0: 	lastDC = thisblockrow[-1][0];
michael@0: 	for (bi = 0; bi < ndummy; bi++) {
michael@0: 	  thisblockrow[bi][0] = lastDC;
michael@0: 	}
michael@0:       }
michael@0:     }
michael@0:     /* If at end of image, create dummy block rows as needed.
michael@0:      * The tricky part here is that within each MCU, we want the DC values
michael@0:      * of the dummy blocks to match the last real block's DC value.
michael@0:      * This squeezes a few more bytes out of the resulting file...
michael@0:      */
michael@0:     if (coef->iMCU_row_num == last_iMCU_row) {
michael@0:       blocks_across += ndummy;	/* include lower right corner */
michael@0:       MCUs_across = blocks_across / h_samp_factor;
michael@0:       for (block_row = block_rows; block_row < compptr->v_samp_factor;
michael@0: 	   block_row++) {
michael@0: 	thisblockrow = buffer[block_row];
michael@0: 	lastblockrow = buffer[block_row-1];
michael@0: 	jzero_far((void FAR *) thisblockrow,
michael@0: 		  (size_t) (blocks_across * SIZEOF(JBLOCK)));
michael@0: 	for (MCUindex = 0; MCUindex < MCUs_across; MCUindex++) {
michael@0: 	  lastDC = lastblockrow[h_samp_factor-1][0];
michael@0: 	  for (bi = 0; bi < h_samp_factor; bi++) {
michael@0: 	    thisblockrow[bi][0] = lastDC;
michael@0: 	  }
michael@0: 	  thisblockrow += h_samp_factor; /* advance to next MCU in row */
michael@0: 	  lastblockrow += h_samp_factor;
michael@0: 	}
michael@0:       }
michael@0:     }
michael@0:   }
michael@0:   /* NB: compress_output will increment iMCU_row_num if successful.
michael@0:    * A suspension return will result in redoing all the work above next time.
michael@0:    */
michael@0: 
michael@0:   /* Emit data to the entropy encoder, sharing code with subsequent passes */
michael@0:   return compress_output(cinfo, input_buf);
michael@0: }
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * Process some data in subsequent passes of a multi-pass case.
michael@0:  * We process the equivalent of one fully interleaved MCU row ("iMCU" row)
michael@0:  * per call, ie, v_samp_factor block rows for each component in the scan.
michael@0:  * The data is obtained from the virtual arrays and fed to the entropy coder.
michael@0:  * Returns TRUE if the iMCU row is completed, FALSE if suspended.
michael@0:  *
michael@0:  * NB: input_buf is ignored; it is likely to be a NULL pointer.
michael@0:  */
michael@0: 
michael@0: METHODDEF(boolean)
michael@0: compress_output (j_compress_ptr cinfo, JSAMPIMAGE input_buf)
michael@0: {
michael@0:   my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
michael@0:   JDIMENSION MCU_col_num;	/* index of current MCU within row */
michael@0:   int blkn, ci, xindex, yindex, yoffset;
michael@0:   JDIMENSION start_col;
michael@0:   JBLOCKARRAY buffer[MAX_COMPS_IN_SCAN];
michael@0:   JBLOCKROW buffer_ptr;
michael@0:   jpeg_component_info *compptr;
michael@0: 
michael@0:   /* Align the virtual buffers for the components used in this scan.
michael@0:    * NB: during first pass, this is safe only because the buffers will
michael@0:    * already be aligned properly, so jmemmgr.c won't need to do any I/O.
michael@0:    */
michael@0:   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
michael@0:     compptr = cinfo->cur_comp_info[ci];
michael@0:     buffer[ci] = (*cinfo->mem->access_virt_barray)
michael@0:       ((j_common_ptr) cinfo, coef->whole_image[compptr->component_index],
michael@0:        coef->iMCU_row_num * compptr->v_samp_factor,
michael@0:        (JDIMENSION) compptr->v_samp_factor, FALSE);
michael@0:   }
michael@0: 
michael@0:   /* Loop to process one whole iMCU row */
michael@0:   for (yoffset = coef->MCU_vert_offset; yoffset < coef->MCU_rows_per_iMCU_row;
michael@0:        yoffset++) {
michael@0:     for (MCU_col_num = coef->mcu_ctr; MCU_col_num < cinfo->MCUs_per_row;
michael@0: 	 MCU_col_num++) {
michael@0:       /* Construct list of pointers to DCT blocks belonging to this MCU */
michael@0:       blkn = 0;			/* index of current DCT block within MCU */
michael@0:       for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
michael@0: 	compptr = cinfo->cur_comp_info[ci];
michael@0: 	start_col = MCU_col_num * compptr->MCU_width;
michael@0: 	for (yindex = 0; yindex < compptr->MCU_height; yindex++) {
michael@0: 	  buffer_ptr = buffer[ci][yindex+yoffset] + start_col;
michael@0: 	  for (xindex = 0; xindex < compptr->MCU_width; xindex++) {
michael@0: 	    coef->MCU_buffer[blkn++] = buffer_ptr++;
michael@0: 	  }
michael@0: 	}
michael@0:       }
michael@0:       /* Try to write the MCU. */
michael@0:       if (! (*cinfo->entropy->encode_mcu) (cinfo, coef->MCU_buffer)) {
michael@0: 	/* Suspension forced; update state counters and exit */
michael@0: 	coef->MCU_vert_offset = yoffset;
michael@0: 	coef->mcu_ctr = MCU_col_num;
michael@0: 	return FALSE;
michael@0:       }
michael@0:     }
michael@0:     /* Completed an MCU row, but perhaps not an iMCU row */
michael@0:     coef->mcu_ctr = 0;
michael@0:   }
michael@0:   /* Completed the iMCU row, advance counters for next one */
michael@0:   coef->iMCU_row_num++;
michael@0:   start_iMCU_row(cinfo);
michael@0:   return TRUE;
michael@0: }
michael@0: 
michael@0: #endif /* FULL_COEF_BUFFER_SUPPORTED */
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * Initialize coefficient buffer controller.
michael@0:  */
michael@0: 
michael@0: GLOBAL(void)
michael@0: jinit_c_coef_controller (j_compress_ptr cinfo, boolean need_full_buffer)
michael@0: {
michael@0:   my_coef_ptr coef;
michael@0: 
michael@0:   coef = (my_coef_ptr)
michael@0:     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
michael@0: 				SIZEOF(my_coef_controller));
michael@0:   cinfo->coef = (struct jpeg_c_coef_controller *) coef;
michael@0:   coef->pub.start_pass = start_pass_coef;
michael@0: 
michael@0:   /* Create the coefficient buffer. */
michael@0:   if (need_full_buffer) {
michael@0: #ifdef FULL_COEF_BUFFER_SUPPORTED
michael@0:     /* Allocate a full-image virtual array for each component, */
michael@0:     /* padded to a multiple of samp_factor DCT blocks in each direction. */
michael@0:     int ci;
michael@0:     jpeg_component_info *compptr;
michael@0: 
michael@0:     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
michael@0: 	 ci++, compptr++) {
michael@0:       coef->whole_image[ci] = (*cinfo->mem->request_virt_barray)
michael@0: 	((j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
michael@0: 	 (JDIMENSION) jround_up((long) compptr->width_in_blocks,
michael@0: 				(long) compptr->h_samp_factor),
michael@0: 	 (JDIMENSION) jround_up((long) compptr->height_in_blocks,
michael@0: 				(long) compptr->v_samp_factor),
michael@0: 	 (JDIMENSION) compptr->v_samp_factor);
michael@0:     }
michael@0: #else
michael@0:     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
michael@0: #endif
michael@0:   } else {
michael@0:     /* We only need a single-MCU buffer. */
michael@0:     JBLOCKROW buffer;
michael@0:     int i;
michael@0: 
michael@0:     buffer = (JBLOCKROW)
michael@0:       (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
michael@0: 				  C_MAX_BLOCKS_IN_MCU * SIZEOF(JBLOCK));
michael@0:     for (i = 0; i < C_MAX_BLOCKS_IN_MCU; i++) {
michael@0:       coef->MCU_buffer[i] = buffer + i;
michael@0:     }
michael@0:     coef->whole_image[0] = NULL; /* flag for no virtual arrays */
michael@0:   }
michael@0: }