nuclear@14: /*
nuclear@14:  * jcprepct.c
nuclear@14:  *
nuclear@14:  * Copyright (C) 1994-1996, Thomas G. Lane.
nuclear@14:  * This file is part of the Independent JPEG Group's software.
nuclear@14:  * For conditions of distribution and use, see the accompanying README file.
nuclear@14:  *
nuclear@14:  * This file contains the compression preprocessing controller.
nuclear@14:  * This controller manages the color conversion, downsampling,
nuclear@14:  * and edge expansion steps.
nuclear@14:  *
nuclear@14:  * Most of the complexity here is associated with buffering input rows
nuclear@14:  * as required by the downsampler.  See the comments at the head of
nuclear@14:  * jcsample.c for the downsampler's needs.
nuclear@14:  */
nuclear@14: 
nuclear@14: #define JPEG_INTERNALS
nuclear@14: #include "jinclude.h"
nuclear@14: #include "jpeglib.h"
nuclear@14: 
nuclear@14: 
nuclear@14: /* At present, jcsample.c can request context rows only for smoothing.
nuclear@14:  * In the future, we might also need context rows for CCIR601 sampling
nuclear@14:  * or other more-complex downsampling procedures.  The code to support
nuclear@14:  * context rows should be compiled only if needed.
nuclear@14:  */
nuclear@14: #ifdef INPUT_SMOOTHING_SUPPORTED
nuclear@14: #define CONTEXT_ROWS_SUPPORTED
nuclear@14: #endif
nuclear@14: 
nuclear@14: 
nuclear@14: /*
nuclear@14:  * For the simple (no-context-row) case, we just need to buffer one
nuclear@14:  * row group's worth of pixels for the downsampling step.  At the bottom of
nuclear@14:  * the image, we pad to a full row group by replicating the last pixel row.
nuclear@14:  * The downsampler's last output row is then replicated if needed to pad
nuclear@14:  * out to a full iMCU row.
nuclear@14:  *
nuclear@14:  * When providing context rows, we must buffer three row groups' worth of
nuclear@14:  * pixels.  Three row groups are physically allocated, but the row pointer
nuclear@14:  * arrays are made five row groups high, with the extra pointers above and
nuclear@14:  * below "wrapping around" to point to the last and first real row groups.
nuclear@14:  * This allows the downsampler to access the proper context rows.
nuclear@14:  * At the top and bottom of the image, we create dummy context rows by
nuclear@14:  * copying the first or last real pixel row.  This copying could be avoided
nuclear@14:  * by pointer hacking as is done in jdmainct.c, but it doesn't seem worth the
nuclear@14:  * trouble on the compression side.
nuclear@14:  */
nuclear@14: 
nuclear@14: 
nuclear@14: /* Private buffer controller object */
nuclear@14: 
nuclear@14: typedef struct {
nuclear@14:   struct jpeg_c_prep_controller pub; /* public fields */
nuclear@14: 
nuclear@14:   /* Downsampling input buffer.  This buffer holds color-converted data
nuclear@14:    * until we have enough to do a downsample step.
nuclear@14:    */
nuclear@14:   JSAMPARRAY color_buf[MAX_COMPONENTS];
nuclear@14: 
nuclear@14:   JDIMENSION rows_to_go;	/* counts rows remaining in source image */
nuclear@14:   int next_buf_row;		/* index of next row to store in color_buf */
nuclear@14: 
nuclear@14: #ifdef CONTEXT_ROWS_SUPPORTED	/* only needed for context case */
nuclear@14:   int this_row_group;		/* starting row index of group to process */
nuclear@14:   int next_buf_stop;		/* downsample when we reach this index */
nuclear@14: #endif
nuclear@14: } my_prep_controller;
nuclear@14: 
nuclear@14: typedef my_prep_controller * my_prep_ptr;
nuclear@14: 
nuclear@14: 
nuclear@14: /*
nuclear@14:  * Initialize for a processing pass.
nuclear@14:  */
nuclear@14: 
nuclear@14: METHODDEF(void)
nuclear@14: start_pass_prep (j_compress_ptr cinfo, J_BUF_MODE pass_mode)
nuclear@14: {
nuclear@14:   my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
nuclear@14: 
nuclear@14:   if (pass_mode != JBUF_PASS_THRU)
nuclear@14:     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
nuclear@14: 
nuclear@14:   /* Initialize total-height counter for detecting bottom of image */
nuclear@14:   prep->rows_to_go = cinfo->image_height;
nuclear@14:   /* Mark the conversion buffer empty */
nuclear@14:   prep->next_buf_row = 0;
nuclear@14: #ifdef CONTEXT_ROWS_SUPPORTED
nuclear@14:   /* Preset additional state variables for context mode.
nuclear@14:    * These aren't used in non-context mode, so we needn't test which mode.
nuclear@14:    */
nuclear@14:   prep->this_row_group = 0;
nuclear@14:   /* Set next_buf_stop to stop after two row groups have been read in. */
nuclear@14:   prep->next_buf_stop = 2 * cinfo->max_v_samp_factor;
nuclear@14: #endif
nuclear@14: }
nuclear@14: 
nuclear@14: 
nuclear@14: /*
nuclear@14:  * Expand an image vertically from height input_rows to height output_rows,
nuclear@14:  * by duplicating the bottom row.
nuclear@14:  */
nuclear@14: 
nuclear@14: LOCAL(void)
nuclear@14: expand_bottom_edge (JSAMPARRAY image_data, JDIMENSION num_cols,
nuclear@14: 		    int input_rows, int output_rows)
nuclear@14: {
nuclear@14:   register int row;
nuclear@14: 
nuclear@14:   for (row = input_rows; row < output_rows; row++) {
nuclear@14:     jcopy_sample_rows(image_data, input_rows-1, image_data, row,
nuclear@14: 		      1, num_cols);
nuclear@14:   }
nuclear@14: }
nuclear@14: 
nuclear@14: 
nuclear@14: /*
nuclear@14:  * Process some data in the simple no-context case.
nuclear@14:  *
nuclear@14:  * Preprocessor output data is counted in "row groups".  A row group
nuclear@14:  * is defined to be v_samp_factor sample rows of each component.
nuclear@14:  * Downsampling will produce this much data from each max_v_samp_factor
nuclear@14:  * input rows.
nuclear@14:  */
nuclear@14: 
nuclear@14: METHODDEF(void)
nuclear@14: pre_process_data (j_compress_ptr cinfo,
nuclear@14: 		  JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
nuclear@14: 		  JDIMENSION in_rows_avail,
nuclear@14: 		  JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
nuclear@14: 		  JDIMENSION out_row_groups_avail)
nuclear@14: {
nuclear@14:   my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
nuclear@14:   int numrows, ci;
nuclear@14:   JDIMENSION inrows;
nuclear@14:   jpeg_component_info * compptr;
nuclear@14: 
nuclear@14:   while (*in_row_ctr < in_rows_avail &&
nuclear@14: 	 *out_row_group_ctr < out_row_groups_avail) {
nuclear@14:     /* Do color conversion to fill the conversion buffer. */
nuclear@14:     inrows = in_rows_avail - *in_row_ctr;
nuclear@14:     numrows = cinfo->max_v_samp_factor - prep->next_buf_row;
nuclear@14:     numrows = (int) MIN((JDIMENSION) numrows, inrows);
nuclear@14:     (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
nuclear@14: 				       prep->color_buf,
nuclear@14: 				       (JDIMENSION) prep->next_buf_row,
nuclear@14: 				       numrows);
nuclear@14:     *in_row_ctr += numrows;
nuclear@14:     prep->next_buf_row += numrows;
nuclear@14:     prep->rows_to_go -= numrows;
nuclear@14:     /* If at bottom of image, pad to fill the conversion buffer. */
nuclear@14:     if (prep->rows_to_go == 0 &&
nuclear@14: 	prep->next_buf_row < cinfo->max_v_samp_factor) {
nuclear@14:       for (ci = 0; ci < cinfo->num_components; ci++) {
nuclear@14: 	expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
nuclear@14: 			   prep->next_buf_row, cinfo->max_v_samp_factor);
nuclear@14:       }
nuclear@14:       prep->next_buf_row = cinfo->max_v_samp_factor;
nuclear@14:     }
nuclear@14:     /* If we've filled the conversion buffer, empty it. */
nuclear@14:     if (prep->next_buf_row == cinfo->max_v_samp_factor) {
nuclear@14:       (*cinfo->downsample->downsample) (cinfo,
nuclear@14: 					prep->color_buf, (JDIMENSION) 0,
nuclear@14: 					output_buf, *out_row_group_ctr);
nuclear@14:       prep->next_buf_row = 0;
nuclear@14:       (*out_row_group_ctr)++;
nuclear@14:     }
nuclear@14:     /* If at bottom of image, pad the output to a full iMCU height.
nuclear@14:      * Note we assume the caller is providing a one-iMCU-height output buffer!
nuclear@14:      */
nuclear@14:     if (prep->rows_to_go == 0 &&
nuclear@14: 	*out_row_group_ctr < out_row_groups_avail) {
nuclear@14:       for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@14: 	   ci++, compptr++) {
nuclear@14: 	expand_bottom_edge(output_buf[ci],
nuclear@14: 			   compptr->width_in_blocks * DCTSIZE,
nuclear@14: 			   (int) (*out_row_group_ctr * compptr->v_samp_factor),
nuclear@14: 			   (int) (out_row_groups_avail * compptr->v_samp_factor));
nuclear@14:       }
nuclear@14:       *out_row_group_ctr = out_row_groups_avail;
nuclear@14:       break;			/* can exit outer loop without test */
nuclear@14:     }
nuclear@14:   }
nuclear@14: }
nuclear@14: 
nuclear@14: 
nuclear@14: #ifdef CONTEXT_ROWS_SUPPORTED
nuclear@14: 
nuclear@14: /*
nuclear@14:  * Process some data in the context case.
nuclear@14:  */
nuclear@14: 
nuclear@14: METHODDEF(void)
nuclear@14: pre_process_context (j_compress_ptr cinfo,
nuclear@14: 		     JSAMPARRAY input_buf, JDIMENSION *in_row_ctr,
nuclear@14: 		     JDIMENSION in_rows_avail,
nuclear@14: 		     JSAMPIMAGE output_buf, JDIMENSION *out_row_group_ctr,
nuclear@14: 		     JDIMENSION out_row_groups_avail)
nuclear@14: {
nuclear@14:   my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
nuclear@14:   int numrows, ci;
nuclear@14:   int buf_height = cinfo->max_v_samp_factor * 3;
nuclear@14:   JDIMENSION inrows;
nuclear@14: 
nuclear@14:   while (*out_row_group_ctr < out_row_groups_avail) {
nuclear@14:     if (*in_row_ctr < in_rows_avail) {
nuclear@14:       /* Do color conversion to fill the conversion buffer. */
nuclear@14:       inrows = in_rows_avail - *in_row_ctr;
nuclear@14:       numrows = prep->next_buf_stop - prep->next_buf_row;
nuclear@14:       numrows = (int) MIN((JDIMENSION) numrows, inrows);
nuclear@14:       (*cinfo->cconvert->color_convert) (cinfo, input_buf + *in_row_ctr,
nuclear@14: 					 prep->color_buf,
nuclear@14: 					 (JDIMENSION) prep->next_buf_row,
nuclear@14: 					 numrows);
nuclear@14:       /* Pad at top of image, if first time through */
nuclear@14:       if (prep->rows_to_go == cinfo->image_height) {
nuclear@14: 	for (ci = 0; ci < cinfo->num_components; ci++) {
nuclear@14: 	  int row;
nuclear@14: 	  for (row = 1; row <= cinfo->max_v_samp_factor; row++) {
nuclear@14: 	    jcopy_sample_rows(prep->color_buf[ci], 0,
nuclear@14: 			      prep->color_buf[ci], -row,
nuclear@14: 			      1, cinfo->image_width);
nuclear@14: 	  }
nuclear@14: 	}
nuclear@14:       }
nuclear@14:       *in_row_ctr += numrows;
nuclear@14:       prep->next_buf_row += numrows;
nuclear@14:       prep->rows_to_go -= numrows;
nuclear@14:     } else {
nuclear@14:       /* Return for more data, unless we are at the bottom of the image. */
nuclear@14:       if (prep->rows_to_go != 0)
nuclear@14: 	break;
nuclear@14:       /* When at bottom of image, pad to fill the conversion buffer. */
nuclear@14:       if (prep->next_buf_row < prep->next_buf_stop) {
nuclear@14: 	for (ci = 0; ci < cinfo->num_components; ci++) {
nuclear@14: 	  expand_bottom_edge(prep->color_buf[ci], cinfo->image_width,
nuclear@14: 			     prep->next_buf_row, prep->next_buf_stop);
nuclear@14: 	}
nuclear@14: 	prep->next_buf_row = prep->next_buf_stop;
nuclear@14:       }
nuclear@14:     }
nuclear@14:     /* If we've gotten enough data, downsample a row group. */
nuclear@14:     if (prep->next_buf_row == prep->next_buf_stop) {
nuclear@14:       (*cinfo->downsample->downsample) (cinfo,
nuclear@14: 					prep->color_buf,
nuclear@14: 					(JDIMENSION) prep->this_row_group,
nuclear@14: 					output_buf, *out_row_group_ctr);
nuclear@14:       (*out_row_group_ctr)++;
nuclear@14:       /* Advance pointers with wraparound as necessary. */
nuclear@14:       prep->this_row_group += cinfo->max_v_samp_factor;
nuclear@14:       if (prep->this_row_group >= buf_height)
nuclear@14: 	prep->this_row_group = 0;
nuclear@14:       if (prep->next_buf_row >= buf_height)
nuclear@14: 	prep->next_buf_row = 0;
nuclear@14:       prep->next_buf_stop = prep->next_buf_row + cinfo->max_v_samp_factor;
nuclear@14:     }
nuclear@14:   }
nuclear@14: }
nuclear@14: 
nuclear@14: 
nuclear@14: /*
nuclear@14:  * Create the wrapped-around downsampling input buffer needed for context mode.
nuclear@14:  */
nuclear@14: 
nuclear@14: LOCAL(void)
nuclear@14: create_context_buffer (j_compress_ptr cinfo)
nuclear@14: {
nuclear@14:   my_prep_ptr prep = (my_prep_ptr) cinfo->prep;
nuclear@14:   int rgroup_height = cinfo->max_v_samp_factor;
nuclear@14:   int ci, i;
nuclear@14:   jpeg_component_info * compptr;
nuclear@14:   JSAMPARRAY true_buffer, fake_buffer;
nuclear@14: 
nuclear@14:   /* Grab enough space for fake row pointers for all the components;
nuclear@14:    * we need five row groups' worth of pointers for each component.
nuclear@14:    */
nuclear@14:   fake_buffer = (JSAMPARRAY)
nuclear@14:     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@14: 				(cinfo->num_components * 5 * rgroup_height) *
nuclear@14: 				SIZEOF(JSAMPROW));
nuclear@14: 
nuclear@14:   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@14:        ci++, compptr++) {
nuclear@14:     /* Allocate the actual buffer space (3 row groups) for this component.
nuclear@14:      * We make the buffer wide enough to allow the downsampler to edge-expand
nuclear@14:      * horizontally within the buffer, if it so chooses.
nuclear@14:      */
nuclear@14:     true_buffer = (*cinfo->mem->alloc_sarray)
nuclear@14:       ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@14:        (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *
nuclear@14: 		      cinfo->max_h_samp_factor) / compptr->h_samp_factor),
nuclear@14:        (JDIMENSION) (3 * rgroup_height));
nuclear@14:     /* Copy true buffer row pointers into the middle of the fake row array */
nuclear@14:     MEMCOPY(fake_buffer + rgroup_height, true_buffer,
nuclear@14: 	    3 * rgroup_height * SIZEOF(JSAMPROW));
nuclear@14:     /* Fill in the above and below wraparound pointers */
nuclear@14:     for (i = 0; i < rgroup_height; i++) {
nuclear@14:       fake_buffer[i] = true_buffer[2 * rgroup_height + i];
nuclear@14:       fake_buffer[4 * rgroup_height + i] = true_buffer[i];
nuclear@14:     }
nuclear@14:     prep->color_buf[ci] = fake_buffer + rgroup_height;
nuclear@14:     fake_buffer += 5 * rgroup_height; /* point to space for next component */
nuclear@14:   }
nuclear@14: }
nuclear@14: 
nuclear@14: #endif /* CONTEXT_ROWS_SUPPORTED */
nuclear@14: 
nuclear@14: 
nuclear@14: /*
nuclear@14:  * Initialize preprocessing controller.
nuclear@14:  */
nuclear@14: 
nuclear@14: GLOBAL(void)
nuclear@14: jinit_c_prep_controller (j_compress_ptr cinfo, boolean need_full_buffer)
nuclear@14: {
nuclear@14:   my_prep_ptr prep;
nuclear@14:   int ci;
nuclear@14:   jpeg_component_info * compptr;
nuclear@14: 
nuclear@14:   if (need_full_buffer)		/* safety check */
nuclear@14:     ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
nuclear@14: 
nuclear@14:   prep = (my_prep_ptr)
nuclear@14:     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@14: 				SIZEOF(my_prep_controller));
nuclear@14:   cinfo->prep = (struct jpeg_c_prep_controller *) prep;
nuclear@14:   prep->pub.start_pass = start_pass_prep;
nuclear@14: 
nuclear@14:   /* Allocate the color conversion buffer.
nuclear@14:    * We make the buffer wide enough to allow the downsampler to edge-expand
nuclear@14:    * horizontally within the buffer, if it so chooses.
nuclear@14:    */
nuclear@14:   if (cinfo->downsample->need_context_rows) {
nuclear@14:     /* Set up to provide context rows */
nuclear@14: #ifdef CONTEXT_ROWS_SUPPORTED
nuclear@14:     prep->pub.pre_process_data = pre_process_context;
nuclear@14:     create_context_buffer(cinfo);
nuclear@14: #else
nuclear@14:     ERREXIT(cinfo, JERR_NOT_COMPILED);
nuclear@14: #endif
nuclear@14:   } else {
nuclear@14:     /* No context, just make it tall enough for one row group */
nuclear@14:     prep->pub.pre_process_data = pre_process_data;
nuclear@14:     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
nuclear@14: 	 ci++, compptr++) {
nuclear@14:       prep->color_buf[ci] = (*cinfo->mem->alloc_sarray)
nuclear@14: 	((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@14: 	 (JDIMENSION) (((long) compptr->width_in_blocks * DCTSIZE *
nuclear@14: 			cinfo->max_h_samp_factor) / compptr->h_samp_factor),
nuclear@14: 	 (JDIMENSION) cinfo->max_v_samp_factor);
nuclear@14:     }
nuclear@14:   }
nuclear@14: }