/*

* jdsample.c

*

* Copyright (C) 1991-1996, Thomas G. Lane.

* Modified 2002-2008 by Guido Vollbeding.

* 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_v_scaled_size / min_DCT_v_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,

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 outrow;

for (outrow = 0; outrow < cinfo->max_v_samp_factor; outrow++) {

inptr = input_data[outrow];

outptr = output_data[outrow];

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;

}

}

/*

* 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;

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);

/* 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_h_scaled_size) /

cinfo->min_DCT_h_scaled_size;

v_in_group = (compptr->v_samp_factor * compptr->DCT_v_scaled_size) /

cinfo->min_DCT_v_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 case for 2h1v upsampling */

upsample->methods[ci] = h2v1_upsample;

} else if (h_in_group * 2 == h_out_group &&

v_in_group * 2 == v_out_group) {

/* Special case for 2h2v upsampling */

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);

}

}

}