ref: c57c8919e303aaad512a5e603f60d4be22d6afea
dir: /sys/src/cmd/gs/jpeg/jdsample.c/
/*
* jdsample.c
*
* Copyright (C) 1991-1996, 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);
}
}
}