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Diffstat (limited to 'examples/videoscale/vs_4tap.c')
| -rw-r--r-- | examples/videoscale/vs_4tap.c | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/examples/videoscale/vs_4tap.c b/examples/videoscale/vs_4tap.c new file mode 100644 index 0000000..5d9edf4 --- /dev/null +++ b/examples/videoscale/vs_4tap.c @@ -0,0 +1,179 @@ +/* + * 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; + } +} + + |