1 /*
2 * Image Scaling Functions (4 tap)
3 * Copyright (c) 2005 David A. Schleef <ds@schleef.org>
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
17 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
19 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
20 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
21 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
23 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
24 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
25 * POSSIBILITY OF SUCH DAMAGE.
26 */
27
28 #include "vs_image.h"
29 #include "vs_scanline.h"
30
31 #include <liboil/liboil.h>
32 #include <math.h>
33
34 #define SHIFT 10
35
36 int16_t vs_4tap_taps[256][4];
37
vs_4tap_func(double x)38 double vs_4tap_func (double x)
39 {
40 #if 0
41 if (x<-1) return 0;
42 if (x>1) return 0;
43 if (x<0) return 1 + x;
44 return 1 - x;
45 #endif
46 #if 0
47 if (x==0) return 1;
48 return sin(M_PI*x)/(M_PI*x) * (1 - 0.25*x*x);
49 #endif
50 #if 1
51 if (x==0) return 1;
52 return sin(M_PI*x)/(M_PI*x);
53 #endif
54 }
55
56 void
vs_4tap_init(void)57 vs_4tap_init (void)
58 {
59 int i;
60 double a, b, c, d;
61 double sum;
62
63 for(i=0;i<256;i++){
64 a = vs_4tap_func(-1 - i/256.0);
65 b = vs_4tap_func(0 - i/256.0);
66 c = vs_4tap_func(1 - i/256.0);
67 d = vs_4tap_func(2 - i/256.0);
68 sum = a + b + c + d;
69
70 vs_4tap_taps[i][0] = rint((1<<SHIFT)*(a/sum));
71 vs_4tap_taps[i][1] = rint((1<<SHIFT)*(b/sum));
72 vs_4tap_taps[i][2] = rint((1<<SHIFT)*(c/sum));
73 vs_4tap_taps[i][3] = rint((1<<SHIFT)*(d/sum));
74 }
75 }
76
77
78 void
vs_scanline_resample_4tap_Y(uint8_t * dest,uint8_t * src,int n,int * xacc,int increment)79 vs_scanline_resample_4tap_Y (uint8_t *dest, uint8_t *src,
80 int n, int *xacc, int increment)
81 {
82 int i;
83 int j;
84 int acc;
85 int x;
86 int y;
87
88 acc = *xacc;
89 for(i=0;i<n;i++){
90 j = acc>>16;
91 x = (acc&0xff00)>>8;
92 y = (vs_4tap_taps[x][0] * src[MAX(j-1,0)] +
93 vs_4tap_taps[x][1] * src[j] +
94 vs_4tap_taps[x][2] * src[j+1] +
95 vs_4tap_taps[x][3] * src[j+2] + (1<<(SHIFT-1))) >> SHIFT;
96 if (y<0) y = 0;
97 if (y>255) y = 255;
98 dest[i] = y;
99 acc += increment;
100 }
101 *xacc = acc;
102 }
103
104 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)105 vs_scanline_merge_4tap_Y (uint8_t *dest, uint8_t *src1, uint8_t *src2,
106 uint8_t *src3, uint8_t *src4, int n, int acc)
107 {
108 int i;
109 int y;
110
111 acc = (acc>>8) & 0xff;
112 for(i=0;i<n;i++){
113 y = (vs_4tap_taps[acc][0] * src1[i] +
114 vs_4tap_taps[acc][1] * src2[i] +
115 vs_4tap_taps[acc][2] * src3[i] +
116 vs_4tap_taps[acc][3] * src4[i] + (1<<(SHIFT-1))) >> SHIFT;
117 if (y<0) y = 0;
118 if (y>255) y = 255;
119 dest[i] = y;
120 }
121
122 }
123
124
125 void
vs_image_scale_4tap_Y(const VSImage * dest,const VSImage * src,uint8_t * tmpbuf)126 vs_image_scale_4tap_Y (const VSImage * dest, const VSImage * src,
127 uint8_t * tmpbuf)
128 {
129 int yacc;
130 int y_increment;
131 int x_increment;
132 int i;
133 int j;
134 int xacc;
135 int k;
136
137 y_increment = ((src->height - 1) << 16) / (dest->height - 1);
138 x_increment = ((src->width - 1) << 16) / (dest->width - 1);
139
140 k = 0;
141 for(i=0;i<4;i++){
142 xacc = 0;
143 vs_scanline_resample_4tap_Y (tmpbuf + i * dest->width,
144 src->pixels + i * src->stride,
145 dest->width, &xacc, x_increment);
146 }
147
148 yacc = 0;
149 for (i = 0; i < dest->height; i++) {
150 uint8_t *t0, *t1, *t2, *t3;
151
152 j = yacc >> 16;
153
154 if (j > k) {
155 k++;
156 if (k + 3 < src->height) {
157 xacc = 0;
158 vs_scanline_resample_4tap_Y (tmpbuf + ((k+3)&3) * dest->width,
159 src->pixels + (k+3) * src->stride,
160 dest->width, &xacc, x_increment);
161 }
162 }
163
164 t0 = tmpbuf + (CLAMP(j - 1, 0, src->height - 1)&3) * dest->width;
165 t1 = tmpbuf + (CLAMP(j , 0, src->height - 1)&3) * dest->width;
166 t2 = tmpbuf + (CLAMP(j + 1, 0, src->height - 1)&3) * dest->width;
167 t3 = tmpbuf + (CLAMP(j + 2, 0, src->height - 1)&3) * dest->width;
168 vs_scanline_merge_4tap_Y (dest->pixels + i*dest->stride,
169 t0, t1, t2, t3, dest->width, yacc & 0xffff);
170
171 yacc += y_increment;
172 }
173 }
174
175
176