gstreamer/gst/videoscale/vs_4tap.c
David Schleef 25d874ec9b gst/videoscale/: Add a 4-tap image scaler. Theoretically looks much prettier.
Original commit message from CVS:
* gst/videoscale/Makefile.am:
* gst/videoscale/gstvideoscale.c:
* gst/videoscale/gstvideoscale.h:
* gst/videoscale/vs_4tap.c:
* gst/videoscale/vs_4tap.h:
* gst/videoscale/vs_image.c:
* gst/videoscale/vs_image.h:
* gst/videoscale/vs_scanline.c:
* gst/videoscale/vs_scanline.h:
Add a 4-tap image scaler.  Theoretically looks much prettier.
The tap calculation could use some improvement.
2006-11-14 23:08:38 +00:00

186 lines
4.7 KiB
C

/*
* Image Scaling Functions (4 tap)
* Copyright (c) 2005 David A. Schleef <ds@schleef.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "vs_image.h"
#include "vs_scanline.h"
#include <liboil/liboil.h>
#include <math.h>
#define SHIFT 10
#define MAX(a,b) (((a) > (b)) ? (a) : (b))
#define MIN(a,b) (((a) < (b)) ? (a) : (b))
#define CLAMP(x,a,b) MAX(MIN((x),(b)),(a))
int16_t vs_4tap_taps[256][4];
double
vs_4tap_func (double x)
{
#if 0
if (x < -1)
return 0;
if (x > 1)
return 0;
if (x < 0)
return 1 + x;
return 1 - x;
#endif
#if 0
if (x == 0)
return 1;
return sin (M_PI * x) / (M_PI * x) * (1 - 0.25 * x * x);
#endif
#if 1
if (x == 0)
return 1;
return sin (M_PI * x) / (M_PI * x);
#endif
}
void
vs_4tap_init (void)
{
int i;
double a, b, c, d;
double sum;
for (i = 0; i < 256; i++) {
a = vs_4tap_func (-1 - i / 256.0);
b = vs_4tap_func (0 - i / 256.0);
c = vs_4tap_func (1 - i / 256.0);
d = vs_4tap_func (2 - i / 256.0);
sum = a + b + c + d;
vs_4tap_taps[i][0] = rint ((1 << SHIFT) * (a / sum));
vs_4tap_taps[i][1] = rint ((1 << SHIFT) * (b / sum));
vs_4tap_taps[i][2] = rint ((1 << SHIFT) * (c / sum));
vs_4tap_taps[i][3] = rint ((1 << SHIFT) * (d / sum));
}
}
void
vs_scanline_resample_4tap_Y (uint8_t * dest, uint8_t * src,
int n, int *xacc, int increment)
{
int i;
int j;
int acc;
int x;
int y;
acc = *xacc;
for (i = 0; i < n; i++) {
j = acc >> 16;
x = (acc & 0xff00) >> 8;
y = (vs_4tap_taps[x][0] * src[MAX (j - 1, 0)] +
vs_4tap_taps[x][1] * src[j] +
vs_4tap_taps[x][2] * src[j + 1] +
vs_4tap_taps[x][3] * src[j + 2] + (1 << (SHIFT - 1))) >> SHIFT;
if (y < 0)
y = 0;
if (y > 255)
y = 255;
dest[i] = y;
acc += increment;
}
*xacc = acc;
}
void
vs_scanline_merge_4tap_Y (uint8_t * dest, uint8_t * src1, uint8_t * src2,
uint8_t * src3, uint8_t * src4, int n, int acc)
{
int i;
int y;
acc = (acc >> 8) & 0xff;
for (i = 0; i < n; i++) {
y = (vs_4tap_taps[acc][0] * src1[i] +
vs_4tap_taps[acc][1] * src2[i] +
vs_4tap_taps[acc][2] * src3[i] +
vs_4tap_taps[acc][3] * src4[i] + (1 << (SHIFT - 1))) >> SHIFT;
if (y < 0)
y = 0;
if (y > 255)
y = 255;
dest[i] = y;
}
}
void
vs_image_scale_4tap_Y (const VSImage * dest, const VSImage * src,
uint8_t * tmpbuf)
{
int yacc;
int y_increment;
int x_increment;
int i;
int j;
int xacc;
int k;
y_increment = ((src->height - 1) << 16) / (dest->height - 1);
x_increment = ((src->width - 1) << 16) / (dest->width - 1);
k = 0;
for (i = 0; i < 4; i++) {
xacc = 0;
vs_scanline_resample_4tap_Y (tmpbuf + i * dest->width,
src->pixels + i * src->stride, dest->width, &xacc, x_increment);
}
yacc = 0;
for (i = 0; i < dest->height; i++) {
uint8_t *t0, *t1, *t2, *t3;
j = yacc >> 16;
if (j > k) {
k++;
if (k + 3 < src->height) {
xacc = 0;
vs_scanline_resample_4tap_Y (tmpbuf + ((k + 3) & 3) * dest->width,
src->pixels + (k + 3) * src->stride,
dest->width, &xacc, x_increment);
}
}
t0 = tmpbuf + (CLAMP (j - 1, 0, src->height - 1) & 3) * dest->width;
t1 = tmpbuf + (CLAMP (j, 0, src->height - 1) & 3) * dest->width;
t2 = tmpbuf + (CLAMP (j + 1, 0, src->height - 1) & 3) * dest->width;
t3 = tmpbuf + (CLAMP (j + 2, 0, src->height - 1) & 3) * dest->width;
vs_scanline_merge_4tap_Y (dest->pixels + i * dest->stride,
t0, t1, t2, t3, dest->width, yacc & 0xffff);
yacc += y_increment;
}
}