/*
 * jdsample.c
 *
 * Copyright (C) 1991-1994, 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 upsampling routines.
 *
 * Upsampling input data is counted in "row groups".  A row group
 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
 * sample rows of each component.  Upsampling will normally produce
 * max_v_samp_factor pixel rows from each row group (but this could vary
 * if the upsampler is applying a scale factor of its own).
 *
 * An excellent reference for image resampling is
 *   Digital Image Warping, George Wolberg, 1990.
 *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
 */

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


/* Pointer to routine to upsample a single component */
typedef JMETHOD ( void, upsample1_ptr,
				  ( j_decompress_ptr cinfo, jpeg_component_info * compptr,
					JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) );

/* Private subobject */

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

	/* Color conversion buffer.  When using separate upsampling and color
	 * conversion steps, this buffer holds one upsampled row group until it
	 * has been color converted and output.
	 * Note: we do not allocate any storage for component(s) which are full-size,
	 * ie do not need rescaling.  The corresponding entry of color_buf[] is
	 * simply set to point to the input data array, thereby avoiding copying.
	 */
	JSAMPARRAY color_buf[MAX_COMPONENTS];

	/* Per-component upsampling method pointers */
	upsample1_ptr methods[MAX_COMPONENTS];

	int next_row_out;   /* counts rows emitted from color_buf */
	JDIMENSION rows_to_go;  /* counts rows remaining in image */

	/* Height of an input row group for each component. */
	int rowgroup_height[MAX_COMPONENTS];

	/* These arrays save pixel expansion factors so that int_expand need not
	 * recompute them each time.  They are unused for other upsampling methods.
	 */
	UINT8 h_expand[MAX_COMPONENTS];
	UINT8 v_expand[MAX_COMPONENTS];
} my_upsampler;

typedef my_upsampler * my_upsample_ptr;


/*
 * Initialize for an upsampling pass.
 */

METHODDEF void
start_pass_upsample( j_decompress_ptr cinfo ) {
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

	/* Mark the conversion buffer empty */
	upsample->next_row_out = cinfo->max_v_samp_factor;
	/* Initialize total-height counter for detecting bottom of image */
	upsample->rows_to_go = cinfo->output_height;
}


/*
 * Control routine to do upsampling (and color conversion).
 *
 * In this version we upsample each component independently.
 * We upsample one row group into the conversion buffer, then apply
 * color conversion a row at a time.
 */

METHODDEF void
sep_upsample( 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_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
	int ci;
	jpeg_component_info * compptr;
	JDIMENSION num_rows;

	/* Fill the conversion buffer, if it's empty */
	if ( upsample->next_row_out >= cinfo->max_v_samp_factor ) {
		for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
			  ci++, compptr++ ) {
			/* Invoke per-component upsample method.  Notice we pass a POINTER
			 * to color_buf[ci], so that fullsize_upsample can change it.
			 */
			( *upsample->methods[ci] )( cinfo, compptr,
										input_buf[ci] + ( *in_row_group_ctr * upsample->rowgroup_height[ci] ),
										upsample->color_buf + ci );
		}
		upsample->next_row_out = 0;
	}

	/* Color-convert and emit rows */

	/* How many we have in the buffer: */
	num_rows = (JDIMENSION) ( cinfo->max_v_samp_factor - upsample->next_row_out );
	/* Not more than the distance to the end of the image.  Need this test
	 * in case the image height is not a multiple of max_v_samp_factor:
	 */
	if ( num_rows > upsample->rows_to_go ) {
		num_rows = upsample->rows_to_go;
	}
	/* And not more than what the client can accept: */
	out_rows_avail -= *out_row_ctr;
	if ( num_rows > out_rows_avail ) {
		num_rows = out_rows_avail;
	}

	( *cinfo->cconvert->color_convert )( cinfo, upsample->color_buf,
										 (JDIMENSION) upsample->next_row_out,
										 output_buf + *out_row_ctr,
										 (int) num_rows );

	/* Adjust counts */
	*out_row_ctr += num_rows;
	upsample->rows_to_go -= num_rows;
	upsample->next_row_out += num_rows;
	/* When the buffer is emptied, declare this input row group consumed */
	if ( upsample->next_row_out >= cinfo->max_v_samp_factor ) {
		( *in_row_group_ctr )++;
	}
}


/*
 * These are the routines invoked by sep_upsample to upsample pixel values
 * of a single component.  One row group is processed per call.
 */


/*
 * For full-size components, we just make color_buf[ci] point at the
 * input buffer, and thus avoid copying any data.  Note that this is
 * safe only because sep_upsample doesn't declare the input row group
 * "consumed" until we are done color converting and emitting it.
 */

METHODDEF void
fullsize_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
				   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
	*output_data_ptr = input_data;
}


/*
 * This is a no-op version used for "uninteresting" components.
 * These components will not be referenced by color conversion.
 */

METHODDEF void
noop_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
			   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
	*output_data_ptr = NULL; /* safety check */
}


/*
 * This version handles any integral sampling ratios.
 * This is not used for typical JPEG files, so it need not be fast.
 * Nor, for that matter, is it particularly accurate: the algorithm is
 * simple replication of the input pixel onto the corresponding output
 * pixels.  The hi-falutin sampling literature refers to this as a
 * "box filter".  A box filter tends to introduce visible artifacts,
 * so if you are actually going to use 3:1 or 4:1 sampling ratios
 * you would be well advised to improve this code.
 */

METHODDEF void
int_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
			  JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
	my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
	JSAMPARRAY output_data = *output_data_ptr;
	register JSAMPROW inptr, outptr;
	register JSAMPLE invalue;
	register int h;
	JSAMPROW outend;
	int h_expand, v_expand;
	int inrow, outrow;

	h_expand = upsample->h_expand[compptr->component_index];
	v_expand = upsample->v_expand[compptr->component_index];

	inrow = outrow = 0;
	while ( outrow < cinfo->max_v_samp_factor ) {
		/* Generate one output row with proper horizontal expansion */
		inptr = input_data[inrow];
		outptr = output_data[outrow];
		outend = outptr + cinfo->output_width;
		while ( outptr < outend ) {
			invalue = *inptr++; /* don't need GETJSAMPLE() here */
			for ( h = h_expand; h > 0; h-- ) {
				*outptr++ = invalue;
			}
		}
		/* Generate any additional output rows by duplicating the first one */
		if ( v_expand > 1 ) {
			jcopy_sample_rows( output_data, outrow, output_data, outrow + 1,
							   v_expand - 1, cinfo->output_width );
		}
		inrow++;
		outrow += v_expand;
	}
}


/*
 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
 * It's still a box filter.
 */

METHODDEF void
h2v1_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
			   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
	JSAMPARRAY output_data = *output_data_ptr;
	register JSAMPROW inptr, outptr;
	register JSAMPLE invalue;
	JSAMPROW outend;
	int inrow;

	for ( inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++ ) {
		inptr = input_data[inrow];
		outptr = output_data[inrow];
		outend = outptr + cinfo->output_width;
		while ( outptr < outend ) {
			invalue = *inptr++; /* don't need GETJSAMPLE() here */
			*outptr++ = invalue;
			*outptr++ = invalue;
		}
	}
}


/*
 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
 * It's still a box filter.
 */

METHODDEF void
h2v2_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
			   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
	JSAMPARRAY output_data = *output_data_ptr;
	register JSAMPROW inptr, outptr;
	register JSAMPLE invalue;
	JSAMPROW outend;
	int inrow, outrow;

	inrow = outrow = 0;
	while ( outrow < cinfo->max_v_samp_factor ) {
		inptr = input_data[inrow];
		outptr = output_data[outrow];
		outend = outptr + cinfo->output_width;
		while ( outptr < outend ) {
			invalue = *inptr++; /* don't need GETJSAMPLE() here */
			*outptr++ = invalue;
			*outptr++ = invalue;
		}
		jcopy_sample_rows( output_data, outrow, output_data, outrow + 1,
						   1, cinfo->output_width );
		inrow++;
		outrow += 2;
	}
}


/*
 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical.
 *
 * The upsampling algorithm is linear interpolation between pixel centers,
 * also known as a "triangle filter".  This is a good compromise between
 * speed and visual quality.  The centers of the output pixels are 1/4 and 3/4
 * of the way between input pixel centers.
 *
 * A note about the "bias" calculations: when rounding fractional values to
 * integer, we do not want to always round 0.5 up to the next integer.
 * If we did that, we'd introduce a noticeable bias towards larger values.
 * Instead, this code is arranged so that 0.5 will be rounded up or down at
 * alternate pixel locations (a simple ordered dither pattern).
 */

METHODDEF void
h2v1_fancy_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
					 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
	JSAMPARRAY output_data = *output_data_ptr;
	register JSAMPROW inptr, outptr;
	register int invalue;
	register JDIMENSION colctr;
	int inrow;

	for ( inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++ ) {
		inptr = input_data[inrow];
		outptr = output_data[inrow];
		/* Special case for first column */
		invalue = GETJSAMPLE( *inptr++ );
		*outptr++ = (JSAMPLE) invalue;
		*outptr++ = (JSAMPLE) ( ( invalue * 3 + GETJSAMPLE( *inptr ) + 2 ) >> 2 );

		for ( colctr = compptr->downsampled_width - 2; colctr > 0; colctr-- ) {
			/* General case: 3/4 * nearer pixel + 1/4 * further pixel */
			invalue = GETJSAMPLE( *inptr++ ) * 3;
			*outptr++ = (JSAMPLE) ( ( invalue + GETJSAMPLE( inptr[-2] ) + 1 ) >> 2 );
			*outptr++ = (JSAMPLE) ( ( invalue + GETJSAMPLE( *inptr ) + 2 ) >> 2 );
		}

		/* Special case for last column */
		invalue = GETJSAMPLE( *inptr );
		*outptr++ = (JSAMPLE) ( ( invalue * 3 + GETJSAMPLE( inptr[-1] ) + 1 ) >> 2 );
		*outptr++ = (JSAMPLE) invalue;
	}
}


/*
 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical.
 * Again a triangle filter; see comments for h2v1 case, above.
 *
 * It is OK for us to reference the adjacent input rows because we demanded
 * context from the main buffer controller (see initialization code).
 */

METHODDEF void
h2v2_fancy_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
					 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
	JSAMPARRAY output_data = *output_data_ptr;
	register JSAMPROW inptr0, inptr1, outptr;
#if BITS_IN_JSAMPLE == 8
	register int thiscolsum, lastcolsum, nextcolsum;
#else
	register INT32 thiscolsum, lastcolsum, nextcolsum;
#endif
	register JDIMENSION colctr;
	int inrow, outrow, v;

	inrow = outrow = 0;
	while ( outrow < cinfo->max_v_samp_factor ) {
		for ( v = 0; v < 2; v++ ) {
			/* inptr0 points to nearest input row, inptr1 points to next nearest */
			inptr0 = input_data[inrow];
			if ( v == 0 ) { /* next nearest is row above */
				inptr1 = input_data[inrow - 1];
			} else { /* next nearest is row below */
				inptr1 = input_data[inrow + 1];
			}
			outptr = output_data[outrow++];

			/* Special case for first column */
			thiscolsum = GETJSAMPLE( *inptr0++ ) * 3 + GETJSAMPLE( *inptr1++ );
			nextcolsum = GETJSAMPLE( *inptr0++ ) * 3 + GETJSAMPLE( *inptr1++ );
			*outptr++ = (JSAMPLE) ( ( thiscolsum * 4 + 8 ) >> 4 );
			*outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + nextcolsum + 7 ) >> 4 );
			lastcolsum = thiscolsum; thiscolsum = nextcolsum;

			for ( colctr = compptr->downsampled_width - 2; colctr > 0; colctr-- ) {
				/* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */
				/* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */
				nextcolsum = GETJSAMPLE( *inptr0++ ) * 3 + GETJSAMPLE( *inptr1++ );
				*outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + lastcolsum + 8 ) >> 4 );
				*outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + nextcolsum + 7 ) >> 4 );
				lastcolsum = thiscolsum; thiscolsum = nextcolsum;
			}

			/* Special case for last column */
			*outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + lastcolsum + 8 ) >> 4 );
			*outptr++ = (JSAMPLE) ( ( thiscolsum * 4 + 7 ) >> 4 );
		}
		inrow++;
	}
}


/*
 * Module initialization routine for upsampling.
 */

GLOBAL void
jinit_upsampler( j_decompress_ptr cinfo ) {
	my_upsample_ptr upsample;
	int ci;
	jpeg_component_info * compptr;
	boolean need_buffer, do_fancy;
	int h_in_group, v_in_group, h_out_group, v_out_group;

	upsample = (my_upsample_ptr)
				( *cinfo->mem->alloc_small ) ( (j_common_ptr) cinfo, JPOOL_IMAGE,
											   SIZEOF( my_upsampler ) );
	cinfo->upsample = (struct jpeg_upsampler *) upsample;
	upsample->pub.start_pass = start_pass_upsample;
	upsample->pub.upsample = sep_upsample;
	upsample->pub.need_context_rows = FALSE; /* until we find out differently */

	if ( cinfo->CCIR601_sampling ) { /* this isn't supported */
		ERREXIT( cinfo, JERR_CCIR601_NOTIMPL );
	}

	/* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1,
	 * so don't ask for it.
	 */
	do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1;

	/* Verify we can handle the sampling factors, select per-component methods,
	 * and create storage as needed.
	 */
	for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
		  ci++, compptr++ ) {
		/* Compute size of an "input group" after IDCT scaling.  This many samples
		 * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
		 */
		h_in_group = ( compptr->h_samp_factor * compptr->DCT_scaled_size ) /
					 cinfo->min_DCT_scaled_size;
		v_in_group = ( compptr->v_samp_factor * compptr->DCT_scaled_size ) /
					 cinfo->min_DCT_scaled_size;
		h_out_group = cinfo->max_h_samp_factor;
		v_out_group = cinfo->max_v_samp_factor;
		upsample->rowgroup_height[ci] = v_in_group; /* save for use later */
		need_buffer = TRUE;
		if ( !compptr->component_needed ) {
			/* Don't bother to upsample an uninteresting component. */
			upsample->methods[ci] = noop_upsample;
			need_buffer = FALSE;
		} else if ( h_in_group == h_out_group && v_in_group == v_out_group ) {
			/* Fullsize components can be processed without any work. */
			upsample->methods[ci] = fullsize_upsample;
			need_buffer = FALSE;
		} else if ( h_in_group * 2 == h_out_group &&
					v_in_group == v_out_group ) {
			/* Special cases for 2h1v upsampling */
			if ( do_fancy && compptr->downsampled_width > 2 ) {
				upsample->methods[ci] = h2v1_fancy_upsample;
			} else {
				upsample->methods[ci] = h2v1_upsample;
			}
		} else if ( h_in_group * 2 == h_out_group &&
					v_in_group * 2 == v_out_group ) {
			/* Special cases for 2h2v upsampling */
			if ( do_fancy && compptr->downsampled_width > 2 ) {
				upsample->methods[ci] = h2v2_fancy_upsample;
				upsample->pub.need_context_rows = TRUE;
			} else {
				upsample->methods[ci] = h2v2_upsample;
			}
		} else if ( ( h_out_group % h_in_group ) == 0 &&
					( v_out_group % v_in_group ) == 0 ) {
			/* Generic integral-factors upsampling method */
			upsample->methods[ci] = int_upsample;
			upsample->h_expand[ci] = (UINT8) ( h_out_group / h_in_group );
			upsample->v_expand[ci] = (UINT8) ( v_out_group / v_in_group );
		} else {
			ERREXIT( cinfo, JERR_FRACT_SAMPLE_NOTIMPL );
		}
		if ( need_buffer ) {
			upsample->color_buf[ci] = ( *cinfo->mem->alloc_sarray )
				( (j_common_ptr) cinfo, JPOOL_IMAGE,
				(JDIMENSION) jround_up( (long) cinfo->output_width,
										(long) cinfo->max_h_samp_factor ),
				(JDIMENSION) cinfo->max_v_samp_factor );
		}
	}
}
