/*
 * jcprepct.c
 *
 * This file is part of the Independent JPEG Group's software:
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * It was modified by The libjpeg-turbo Project to include only code relevant
 * to libjpeg-turbo.
 * For conditions of distribution and use, see the accompanying README.ijg
 * 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);
		}
	}
}
