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