/*
 * jdpostct.c
 *
 * Copyright (C) 1994-1995, 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 decompression postprocessing controller.
 * This controller manages the upsampling, color conversion, and color
 * quantization/reduction steps; specifically, it controls the buffering
 * between upsample/color conversion and color quantization/reduction.
 *
 * If no color quantization/reduction is required, then this module has no
 * work to do, and it just hands off to the upsample/color conversion code.
 * An integrated upsample/convert/quantize process would replace this module
 * entirely.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/* Private buffer controller object */

typedef struct {
	struct jpeg_d_post_controller pub; /* public fields */

	/* Color quantization source buffer: this holds output data from
	 * the upsample/color conversion step to be passed to the quantizer.
	 * For two-pass color quantization, we need a full-image buffer;
	 * for one-pass operation, a strip buffer is sufficient.
	 */
	jvirt_sarray_ptr whole_image; /* virtual array, or NULL if one-pass */
	JSAMPARRAY buffer;      /* strip buffer, or current strip of virtual */
	JDIMENSION strip_height; /* buffer size in rows */
	/* for two-pass mode only: */
	JDIMENSION starting_row; /* row # of first row in current strip */
	JDIMENSION next_row;    /* index of next row to fill/empty in strip */
} my_post_controller;

typedef my_post_controller * my_post_ptr;


/* Forward declarations */
METHODDEF void post_process_1pass
JPP( ( j_decompress_ptr cinfo,
	   JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
	   JDIMENSION in_row_groups_avail,
	   JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
	   JDIMENSION out_rows_avail ) );
#ifdef QUANT_2PASS_SUPPORTED
METHODDEF void post_process_prepass
JPP( ( j_decompress_ptr cinfo,
	   JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
	   JDIMENSION in_row_groups_avail,
	   JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
	   JDIMENSION out_rows_avail ) );
METHODDEF void post_process_2pass
JPP( ( j_decompress_ptr cinfo,
	   JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
	   JDIMENSION in_row_groups_avail,
	   JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
	   JDIMENSION out_rows_avail ) );
#endif


/*
 * Initialize for a processing pass.
 */

METHODDEF void
start_pass_dpost( j_decompress_ptr cinfo, J_BUF_MODE pass_mode ) {
	my_post_ptr post = (my_post_ptr) cinfo->post;

	switch ( pass_mode ) {
	case JBUF_PASS_THRU:
		if ( cinfo->quantize_colors ) {
			/* Single-pass processing with color quantization. */
			post->pub.post_process_data = post_process_1pass;
			/* We could be doing buffered-image output before starting a 2-pass
			 * color quantization; in that case, jinit_d_post_controller did not
			 * allocate a strip buffer.  Use the virtual-array buffer as workspace.
			 */
			if ( post->buffer == NULL ) {
				post->buffer = ( *cinfo->mem->access_virt_sarray )
				  ( (j_common_ptr) cinfo, post->whole_image,
				  (JDIMENSION) 0, post->strip_height, TRUE );
			}
		} else {
			/* For single-pass processing without color quantization,
			 * I have no work to do; just call the upsampler directly.
			 */
			post->pub.post_process_data = cinfo->upsample->upsample;
		}
		break;
#ifdef QUANT_2PASS_SUPPORTED
	case JBUF_SAVE_AND_PASS:
		/* First pass of 2-pass quantization */
		if ( post->whole_image == NULL ) {
			ERREXIT( cinfo, JERR_BAD_BUFFER_MODE );
		}
		post->pub.post_process_data = post_process_prepass;
		break;
	case JBUF_CRANK_DEST:
		/* Second pass of 2-pass quantization */
		if ( post->whole_image == NULL ) {
			ERREXIT( cinfo, JERR_BAD_BUFFER_MODE );
		}
		post->pub.post_process_data = post_process_2pass;
		break;
#endif /* QUANT_2PASS_SUPPORTED */
	default:
		ERREXIT( cinfo, JERR_BAD_BUFFER_MODE );
		break;
	}
	post->starting_row = post->next_row = 0;
}


/*
 * Process some data in the one-pass (strip buffer) case.
 * This is used for color precision reduction as well as one-pass quantization.
 */

METHODDEF void
post_process_1pass( j_decompress_ptr cinfo,
					JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
					JDIMENSION in_row_groups_avail,
					JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
					JDIMENSION out_rows_avail ) {
	my_post_ptr post = (my_post_ptr) cinfo->post;
	JDIMENSION num_rows, max_rows;

	/* Fill the buffer, but not more than what we can dump out in one go. */
	/* Note we rely on the upsampler to detect bottom of image. */
	max_rows = out_rows_avail - *out_row_ctr;
	if ( max_rows > post->strip_height ) {
		max_rows = post->strip_height;
	}
	num_rows = 0;
	( *cinfo->upsample->upsample )( cinfo,
									input_buf, in_row_group_ctr, in_row_groups_avail,
									post->buffer, &num_rows, max_rows );
	/* Quantize and emit data. */
	( *cinfo->cquantize->color_quantize )( cinfo,
										   post->buffer, output_buf + *out_row_ctr, (int) num_rows );
	*out_row_ctr += num_rows;
}


#ifdef QUANT_2PASS_SUPPORTED

/*
 * Process some data in the first pass of 2-pass quantization.
 */

METHODDEF void
post_process_prepass( j_decompress_ptr cinfo,
					  JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
					  JDIMENSION in_row_groups_avail,
					  JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
					  JDIMENSION out_rows_avail ) {
	my_post_ptr post = (my_post_ptr) cinfo->post;
	JDIMENSION old_next_row, num_rows;

	/* Reposition virtual buffer if at start of strip. */
	if ( post->next_row == 0 ) {
		post->buffer = ( *cinfo->mem->access_virt_sarray )
				( (j_common_ptr) cinfo, post->whole_image,
				post->starting_row, post->strip_height, TRUE );
	}

	/* Upsample some data (up to a strip height's worth). */
	old_next_row = post->next_row;
	( *cinfo->upsample->upsample )( cinfo,
									input_buf, in_row_group_ctr, in_row_groups_avail,
									post->buffer, &post->next_row, post->strip_height );

	/* Allow quantizer to scan new data.  No data is emitted, */
	/* but we advance out_row_ctr so outer loop can tell when we're done. */
	if ( post->next_row > old_next_row ) {
		num_rows = post->next_row - old_next_row;
		( *cinfo->cquantize->color_quantize )( cinfo, post->buffer + old_next_row,
											   (JSAMPARRAY) NULL, (int) num_rows );
		*out_row_ctr += num_rows;
	}

	/* Advance if we filled the strip. */
	if ( post->next_row >= post->strip_height ) {
		post->starting_row += post->strip_height;
		post->next_row = 0;
	}
}


/*
 * Process some data in the second pass of 2-pass quantization.
 */

METHODDEF void
post_process_2pass( j_decompress_ptr cinfo,
					JSAMPIMAGE input_buf, JDIMENSION *in_row_group_ctr,
					JDIMENSION in_row_groups_avail,
					JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
					JDIMENSION out_rows_avail ) {
	my_post_ptr post = (my_post_ptr) cinfo->post;
	JDIMENSION num_rows, max_rows;

	/* Reposition virtual buffer if at start of strip. */
	if ( post->next_row == 0 ) {
		post->buffer = ( *cinfo->mem->access_virt_sarray )
				( (j_common_ptr) cinfo, post->whole_image,
				post->starting_row, post->strip_height, FALSE );
	}

	/* Determine number of rows to emit. */
	num_rows = post->strip_height - post->next_row; /* available in strip */
	max_rows = out_rows_avail - *out_row_ctr; /* available in output area */
	if ( num_rows > max_rows ) {
		num_rows = max_rows;
	}
	/* We have to check bottom of image here, can't depend on upsampler. */
	max_rows = cinfo->output_height - post->starting_row;
	if ( num_rows > max_rows ) {
		num_rows = max_rows;
	}

	/* Quantize and emit data. */
	( *cinfo->cquantize->color_quantize )( cinfo,
										   post->buffer + post->next_row, output_buf + *out_row_ctr,
										   (int) num_rows );
	*out_row_ctr += num_rows;

	/* Advance if we filled the strip. */
	post->next_row += num_rows;
	if ( post->next_row >= post->strip_height ) {
		post->starting_row += post->strip_height;
		post->next_row = 0;
	}
}

#endif /* QUANT_2PASS_SUPPORTED */


/*
 * Initialize postprocessing controller.
 */

GLOBAL void
jinit_d_post_controller( j_decompress_ptr cinfo, boolean need_full_buffer ) {
	my_post_ptr post;

	post = (my_post_ptr)
				( *cinfo->mem->alloc_small ) ( (j_common_ptr) cinfo, JPOOL_IMAGE,
											   SIZEOF( my_post_controller ) );
	cinfo->post = (struct jpeg_d_post_controller *) post;
	post->pub.start_pass = start_pass_dpost;
	post->whole_image = NULL; /* flag for no virtual arrays */
	post->buffer = NULL;    /* flag for no strip buffer */

	/* Create the quantization buffer, if needed */
	if ( cinfo->quantize_colors ) {
		/* The buffer strip height is max_v_samp_factor, which is typically
		 * an efficient number of rows for upsampling to return.
		 * (In the presence of output rescaling, we might want to be smarter?)
		 */
		post->strip_height = (JDIMENSION) cinfo->max_v_samp_factor;
		if ( need_full_buffer ) {
			/* Two-pass color quantization: need full-image storage. */
			/* We round up the number of rows to a multiple of the strip height. */
#ifdef QUANT_2PASS_SUPPORTED
			post->whole_image = ( *cinfo->mem->request_virt_sarray )
				( (j_common_ptr) cinfo, JPOOL_IMAGE, FALSE,
				cinfo->output_width * cinfo->out_color_components,
				(JDIMENSION) jround_up( (long) cinfo->output_height,
										(long) post->strip_height ),
				post->strip_height );
#else
			ERREXIT( cinfo, JERR_BAD_BUFFER_MODE );
#endif /* QUANT_2PASS_SUPPORTED */
		} else {
			/* One-pass color quantization: just make a strip buffer. */
			post->buffer = ( *cinfo->mem->alloc_sarray )
				( (j_common_ptr) cinfo, JPOOL_IMAGE,
				cinfo->output_width * cinfo->out_color_components,
				post->strip_height );
		}
	}
}
