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 /*

  * jcprepct.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 compression preprocessing controller.

  * This controller manages the color conversion, downsampling,

  * and edge expansion steps.

  *

  * Most of the complexity here is associated with buffering input rows

  * as required by the downsampler.  See the comments at the head of

  * jcsample.c for the downsampler's needs.

  */

 #define JPEG_INTERNALS

 #include "jinclude.h"

 #include "jpeglib.h"

 /* At present, jcsample.c can request context rows only for smoothing.

  * In the future, we might also need context rows for CCIR601 sampling

  * or other more-complex downsampling procedures.  The code to support

  * context rows should be compiled only if needed.

  */

 #ifdef INPUT_SMOOTHING_SUPPORTED

 #define CONTEXT_ROWS_SUPPORTED

 #endif

 /*

  * For the simple (no-context-row) case, we just need to buffer one

  * row group's worth of pixels for the downsampling step.  At the bottom of

  * the image, we pad to a full row group by replicating the last pixel row.

  * The downsampler's last output row is then replicated if needed to pad

  * out to a full iMCU row.

  *

  * When providing context rows, we must buffer three row groups' worth of

  * pixels.  Three row groups are physically allocated, but the row pointer

  * arrays are made five row groups high, with the extra pointers above and

  * below "wrapping around" to point to the last and first real row groups.

  * This allows the downsampler to access the proper context rows.

  * At the top and bottom of the image, we create dummy context rows by

  * copying the first or last real pixel row.  This copying could be avoided

  * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the

  * trouble on the compression side.

  */

 /* Private buffer controller object */

 typedef struct {

   struct jpeg_c_prep_controller pub; /* public fields */

   /* Downsampling input buffer.  This buffer holds color-converted data

    * until we have enough to do a downsample step.

    */

   JSAMPARRAY color_buf[MAX_COMPONENTS];

   JDIMENSION rows_to_go;	/* counts rows remaining in source image */

   int next_buf_row;		/* index of next row to store in color_buf */

 #ifdef CONTEXT_ROWS_SUPPORTED	/* only needed for context case */

   int this_row_group;		/* starting row index of group to process */

   int next_buf_stop;		/* downsample when we reach this index */

 #endif

 } my_prep_controller;

 typedef my_prep_controller * my_prep_ptr;

 /*

  * Initialize for a processing pass.

  */

 METHODDEF(void)

 start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode)

 {

   my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

   if (pass_mode != JBUF_PASS_THRU)

     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);

   /* Initialize total-height counter for detecting bottom of image */

   prep->rows_to_go = cinfo->image_height;

   /* Mark the conversion buffer empty */

   prep->next_buf_row = 0;

 #ifdef CONTEXT_ROWS_SUPPORTED

   /* Preset additional state variables for context mode.

    * These aren't used in non-context mode, so we needn't test which mode.

    */

   prep->this_row_group = 0;

   /* Set next_buf_stop to stop after two row groups have been read in. */

   prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;

 #endif

 }

 /*

  * Expand an image vertically from height input_rows to height output_rows,

  * by duplicating the bottom row.

  */

 LOCAL(void)

 expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,

 		    int input_rows, int output_rows)

 {

   register int row;

   for (row = input_rows; row < output_rows; row++) {

     jcopy_sample_rows(image_data, input_rows-1, image_data, row,

 		      1, num_cols);

   }

 }

 /*

  * Process some data in the simple no-context case.

  *

  * Preprocessor output data is counted in "row groups".  A row group

  * is defined to be v_samp_factor sample rows of each component.

  * Downsampling will produce this much data from each max_v_samp_factor

  * input rows.

  */

 METHODDEF(void)

 pre_process_data (j_compress_ptr cinfo,

 		  JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,

 		  JDIMENSION in_rows_avail,

 		  JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,

 		  JDIMENSION out_row_groups_avail)

 {

   my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

   int numrows, ci;

   JDIMENSION inrows;

   jpeg_component_info * compptr;

   while (*in_row_ctr < in_rows_avail &&

 	 *out_row_group_ctr < out_row_groups_avail) {

     /* Do color conversion to fill the conversion buffer. */

     inrows = in_rows_avail - *in_row_ctr;

     numrows = cinfo->max_v_samp_factor - prep->next_buf_row;

     numrows = (int) MIN((JDIMENSION) numrows, inrows);

     (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,

 				       prep->color_buf,

 				       (JDIMENSION) prep->next_buf_row,

 				       numrows);

     *in_row_ctr += numrows;

     prep->next_buf_row += numrows;

     prep->rows_to_go -= numrows;

     /* If at bottom of image, pad to fill the conversion buffer. */

     if (prep->rows_to_go == 0 &&

 	prep->next_buf_row < cinfo->max_v_samp_factor) {

       for (ci = 0; ci < cinfo->num_components; ci++) {

 	expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,

 			   prep->next_buf_row, cinfo->max_v_samp_factor);

       }

       prep->next_buf_row = cinfo->max_v_samp_factor;

     }

     /* If we've filled the conversion buffer, empty it. */

     if (prep->next_buf_row == cinfo->max_v_samp_factor) {

       (*cinfo->downsample->downsample) (cinfo,

 					prep->color_buf, (JDIMENSION) 0,

 					output_buf, *out_row_group_ctr);

       prep->next_buf_row = 0;

       (*out_row_group_ctr)++;

     }

     /* If at bottom of image, pad the output to a full iMCU height.

      * Note we assume the caller is providing a one-iMCU-height output buffer!

      */

     if (prep->rows_to_go == 0 &&

 	*out_row_group_ctr < out_row_groups_avail) {

       for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

 	   ci++, compptr++) {

 	expand_bottom_edge(output_buf[ci],

 			   compptr->width_in_blocks * DCTSIZE,

 			   (int) (*out_row_group_ctr * compptr->v_samp_factor),

 			   (int) (out_row_groups_avail * compptr->v_samp_factor));

       }

       *out_row_group_ctr = out_row_groups_avail;

       break;			/* can exit outer loop without test */

     }

   }

 }

 #ifdef CONTEXT_ROWS_SUPPORTED

 /*

  * Process some data in the context case.

  */

 METHODDEF(void)

 pre_process_context (j_compress_ptr cinfo,

 		     JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,

 		     JDIMENSION in_rows_avail,

 		     JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,

 		     JDIMENSION out_row_groups_avail)

 {

   my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

   int numrows, ci;

   int buf_height = cinfo->max_v_samp_factor * 3;

   JDIMENSION inrows;

   while (*out_row_group_ctr < out_row_groups_avail) {

     if (*in_row_ctr < in_rows_avail) {

       /* Do color conversion to fill the conversion buffer. */

       inrows = in_rows_avail - *in_row_ctr;

       numrows = prep->next_buf_stop - prep->next_buf_row;

       numrows = (int) MIN((JDIMENSION) numrows, inrows);

       (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,

 					 prep->color_buf,

 					 (JDIMENSION) prep->next_buf_row,

 					 numrows);

       /* Pad at top of image, if first time through */

       if (prep->rows_to_go == cinfo->image_height) {

 	for (ci = 0; ci < cinfo->num_components; ci++) {

 	  int row;

 	  for (row = 1; row <= cinfo->max_v_samp_factor; row++) {

 	    jcopy_sample_rows(prep->color_buf[ci], 0,

 			      prep->color_buf[ci], -row,

 			      1, cinfo->image_width);

 	  }

 	}

       }

       *in_row_ctr += numrows;

       prep->next_buf_row += numrows;

       prep->rows_to_go -= numrows;

     } else {

       /* Return for more data, unless we are at the bottom of the image. */

       if (prep->rows_to_go != 0)

 	break;

       /* When at bottom of image, pad to fill the conversion buffer. */

       if (prep->next_buf_row < prep->next_buf_stop) {

 	for (ci = 0; ci < cinfo->num_components; ci++) {

 	  expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,

 			     prep->next_buf_row, prep->next_buf_stop);

 	}

 	prep->next_buf_row = prep->next_buf_stop;

       }

     }

     /* If we've gotten enough data, downsample a row group. */

     if (prep->next_buf_row == prep->next_buf_stop) {

       (*cinfo->downsample->downsample) (cinfo,

 					prep->color_buf,

 					(JDIMENSION) prep->this_row_group,

 					output_buf, *out_row_group_ctr);

       (*out_row_group_ctr)++;

       /* Advance pointers with wraparound as necessary. */

       prep->this_row_group += cinfo->max_v_samp_factor;

       if (prep->this_row_group >= buf_height)

 	prep->this_row_group = 0;

       if (prep->next_buf_row >= buf_height)

 	prep->next_buf_row = 0;

       prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;

     }

   }

 }

 /*

  * Create the wrapped-around downsampling input buffer needed for context mode.

  */

 LOCAL(void)

 create_context_buffer (j_compress_ptr cinfo)

 {

   my_prep_ptr prep = (my_prep_ptr) cinfo->prep;

   int rgroup_height = cinfo->max_v_samp_factor;

   int ci, i;

   jpeg_component_info * compptr;

   JSAMPARRAY true_buffer, fake_buffer;

   /* Grab enough space for fake row pointers for all the components;

    * we need five row groups' worth of pointers for each component.

    */

   fake_buffer = (JSAMPARRAY)

     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

 				(cinfo->num_components * 5 * rgroup_height) *

 				SIZEOF(JSAMPROW));

   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

        ci++, compptr++) {

     /* Allocate the actual buffer space (3 row groups) for this component.

      * We make the buffer wide enough to allow the downsampler to edge-expand

      * horizontally within the buffer, if it so chooses.

      */

     true_buffer = (*cinfo->mem->alloc_sarray)

       ((j_common_ptr) cinfo, JPOOL_IMAGE,

        (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *

 		      cinfo->max_h_samp_factor) / compptr->h_samp_factor),

        (JDIMENSION) (3 * rgroup_height));

     /* Copy true buffer row pointers into the middle of the fake row array */

     MEMCOPY(fake_buffer + rgroup_height, true_buffer,

 	    3 * rgroup_height * SIZEOF(JSAMPROW));

     /* Fill in the above and below wraparound pointers */

     for (i = 0; i < rgroup_height; i++) {

       fake_buffer[i] = true_buffer[2 * rgroup_height + i];

       fake_buffer[4 * rgroup_height + i] = true_buffer[i];

     }

     prep->color_buf[ci] = fake_buffer + rgroup_height;

     fake_buffer += 5 * rgroup_height; /* point to space for next component */

   }

 }

 #endif /* CONTEXT_ROWS_SUPPORTED */

 /*

  * Initialize preprocessing controller.

  */

 GLOBAL(void)

 jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)

 {

   my_prep_ptr prep;

   int ci;

   jpeg_component_info * compptr;

   if (need_full_buffer)		/* safety check */

     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);

   prep = (my_prep_ptr)

     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

 				SIZEOF(my_prep_controller));

   cinfo->prep = (struct jpeg_c_prep_controller *) prep;

   prep->pub.start_pass = start_pass_prep;

   /* Allocate the color conversion buffer.

    * We make the buffer wide enough to allow the downsampler to edge-expand

    * horizontally within the buffer, if it so chooses.

    */

   if (cinfo->downsample->need_context_rows) {

     /* Set up to provide context rows */

 #ifdef CONTEXT_ROWS_SUPPORTED

     prep->pub.pre_process_data = pre_process_context;

     create_context_buffer(cinfo);

 #else

     ERREXIT(cinfo, JERR_NOT_COMPILED);

 #endif

   } else {

     /* No context, just make it tall enough for one row group */

     prep->pub.pre_process_data = pre_process_data;

     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;

 	 ci++, compptr++) {

       prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)

 	((j_common_ptr) cinfo, JPOOL_IMAGE,

 	 (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *

 			cinfo->max_h_samp_factor) / compptr->h_samp_factor),

 	 (JDIMENSION) cinfo->max_v_samp_factor);

     }

   }

 }