Pillow/libImaging/BcnDecode.c
2016-08-26 02:26:03 -05:00

856 lines
22 KiB
C

/*
* The Python Imaging Library
*
* decoder for DXTn-compressed data
*
* Format documentation:
* http://oss.sgi.com/projects/ogl-sample/registry/EXT/texture_compression_s3tc.txt
*
* The contents of this file are in the public domain (CC0)
* Full text of the CC0 license:
* https://creativecommons.org/publicdomain/zero/1.0/
*/
#include "Imaging.h"
typedef struct {
UINT8 r, g, b, a;
} rgba;
typedef struct {
UINT8 l;
} lum;
typedef struct {
FLOAT32 r, g, b;
} rgb32f;
typedef struct {
UINT16 c0, c1;
UINT32 lut;
} bc1_color;
typedef struct {
UINT8 a0, a1;
UINT8 lut[6];
} bc3_alpha;
#define LOAD16(p) \
(p)[0] | ((p)[1] << 8)
#define LOAD32(p) \
(p)[0] | ((p)[1] << 8) | ((p)[2] << 16) | ((p)[3] << 24)
static void bc1_color_load(bc1_color *dst, const UINT8 *src) {
dst->c0 = LOAD16(src);
dst->c1 = LOAD16(src + 2);
dst->lut = LOAD32(src + 4);
}
static void bc3_alpha_load(bc3_alpha *dst, const UINT8 *src) {
memcpy(dst, src, sizeof(bc3_alpha));
}
static rgba decode_565(UINT16 x) {
rgba c;
int r, g, b;
r = (x & 0xf800) >> 8;
r |= r >> 5;
c.r = r;
g = (x & 0x7e0) >> 3;
g |= g >> 6;
c.g = g;
b = (x & 0x1f) << 3;
b |= b >> 5;
c.b = b;
c.a = 0xff;
return c;
}
static void decode_bc1_color(rgba *dst, const UINT8 *src) {
bc1_color col;
rgba p[4];
int n, cw;
UINT16 r0, g0, b0, r1, g1, b1;
bc1_color_load(&col, src);
p[0] = decode_565(col.c0);
r0 = p[0].r;
g0 = p[0].g;
b0 = p[0].b;
p[1] = decode_565(col.c1);
r1 = p[1].r;
g1 = p[1].g;
b1 = p[1].b;
if (col.c0 > col.c1) {
p[2].r = (2*r0 + 1*r1) / 3;
p[2].g = (2*g0 + 1*g1) / 3;
p[2].b = (2*b0 + 1*b1) / 3;
p[2].a = 0xff;
p[3].r = (1*r0 + 2*r1) / 3;
p[3].g = (1*g0 + 2*g1) / 3;
p[3].b = (1*b0 + 2*b1) / 3;
p[3].a = 0xff;
} else {
p[2].r = (r0 + r1) / 2;
p[2].g = (g0 + g1) / 2;
p[2].b = (b0 + b1) / 2;
p[2].a = 0xff;
p[3].r = 0;
p[3].g = 0;
p[3].b = 0;
p[3].a = 0;
}
for (n = 0; n < 16; n++) {
cw = 3 & (col.lut >> (2 * n));
dst[n] = p[cw];
}
}
static void decode_bc3_alpha(char *dst, const UINT8 *src, int stride, int o) {
bc3_alpha b;
UINT16 a0, a1;
UINT8 a[8];
int n, lut, aw;
bc3_alpha_load(&b, src);
a0 = b.a0;
a1 = b.a1;
a[0] = (UINT8)a0;
a[1] = (UINT8)a1;
if (a0 > a1) {
a[2] = (6*a0 + 1*a1) / 7;
a[3] = (5*a0 + 2*a1) / 7;
a[4] = (4*a0 + 3*a1) / 7;
a[5] = (3*a0 + 4*a1) / 7;
a[6] = (2*a0 + 5*a1) / 7;
a[7] = (1*a0 + 6*a1) / 7;
} else {
a[2] = (4*a0 + 1*a1) / 5;
a[3] = (3*a0 + 2*a1) / 5;
a[4] = (2*a0 + 3*a1) / 5;
a[5] = (1*a0 + 4*a1) / 5;
a[6] = 0;
a[7] = 0xff;
}
lut = b.lut[0] | (b.lut[1] << 8) | (b.lut[2] << 16);
for (n = 0; n < 8; n++) {
aw = 7 & (lut >> (3 * n));
dst[stride * n + o] = a[aw];
}
lut = b.lut[3] | (b.lut[4] << 8) | (b.lut[5] << 16);
for (n = 0; n < 8; n++) {
aw = 7 & (lut >> (3 * n));
dst[stride * (8+n) + o] = a[aw];
}
}
static void decode_bc1_block(rgba *col, const UINT8* src) {
decode_bc1_color(col, src);
}
static void decode_bc2_block(rgba *col, const UINT8* src) {
int n, bitI, byI, av;
decode_bc1_color(col, src + 8);
for (n = 0; n < 16; n++) {
bitI = n * 4;
byI = bitI >> 3;
av = 0xf & (src[byI] >> (bitI & 7));
av = (av << 4) | av;
col[n].a = av;
}
}
static void decode_bc3_block(rgba *col, const UINT8* src) {
decode_bc1_color(col, src + 8);
decode_bc3_alpha((char *)col, src, sizeof(col[0]), 3);
}
static void decode_bc4_block(lum *col, const UINT8* src) {
decode_bc3_alpha((char *)col, src, sizeof(col[0]), 0);
}
static void decode_bc5_block(rgba *col, const UINT8* src) {
decode_bc3_alpha((char *)col, src, sizeof(col[0]), 0);
decode_bc3_alpha((char *)col, src + 8, sizeof(col[0]), 1);
}
/* BC6 and BC7 are described here:
https://www.opengl.org/registry/specs/ARB/texture_compression_bptc.txt */
static UINT8 get_bit(const UINT8* src, int bit) {
int by = bit >> 3;
bit &= 7;
return (src[by] >> bit) & 1;
}
static UINT8 get_bits(const UINT8* src, int bit, int count) {
UINT8 v;
int x;
int by = bit >> 3;
bit &= 7;
if (!count) {
return 0;
}
if (bit + count <= 8) {
v = (src[by] >> bit) & ((1 << count) - 1);
} else {
x = src[by] | (src[by+1] << 8);
v = (x >> bit) & ((1 << count) - 1);
}
return v;
}
/* BC7 */
typedef struct {
char ns;
char pb;
char rb;
char isb;
char cb;
char ab;
char epb;
char spb;
char ib;
char ib2;
} bc7_mode_info;
static const bc7_mode_info bc7_modes[] = {
{3, 4, 0, 0, 4, 0, 1, 0, 3, 0},
{2, 6, 0, 0, 6, 0, 0, 1, 3, 0},
{3, 6, 0, 0, 5, 0, 0, 0, 2, 0},
{2, 6, 0, 0, 7, 0, 1, 0, 2, 0},
{1, 0, 2, 1, 5, 6, 0, 0, 2, 3},
{1, 0, 2, 0, 7, 8, 0, 0, 2, 2},
{1, 0, 0, 0, 7, 7, 1, 0, 4, 0},
{2, 6, 0, 0, 5, 5, 1, 0, 2, 0}
};
/* Subset indices:
Table.P2, 1 bit per index */
static const UINT16 bc7_si2[] = {
0xcccc, 0x8888, 0xeeee, 0xecc8, 0xc880, 0xfeec, 0xfec8, 0xec80,
0xc800, 0xffec, 0xfe80, 0xe800, 0xffe8, 0xff00, 0xfff0, 0xf000,
0xf710, 0x008e, 0x7100, 0x08ce, 0x008c, 0x7310, 0x3100, 0x8cce,
0x088c, 0x3110, 0x6666, 0x366c, 0x17e8, 0x0ff0, 0x718e, 0x399c,
0xaaaa, 0xf0f0, 0x5a5a, 0x33cc, 0x3c3c, 0x55aa, 0x9696, 0xa55a,
0x73ce, 0x13c8, 0x324c, 0x3bdc, 0x6996, 0xc33c, 0x9966, 0x0660,
0x0272, 0x04e4, 0x4e40, 0x2720, 0xc936, 0x936c, 0x39c6, 0x639c,
0x9336, 0x9cc6, 0x817e, 0xe718, 0xccf0, 0x0fcc, 0x7744, 0xee22};
/* Table.P3, 2 bits per index */
static const UINT32 bc7_si3[] = {
0xaa685050, 0x6a5a5040, 0x5a5a4200, 0x5450a0a8,
0xa5a50000, 0xa0a05050, 0x5555a0a0, 0x5a5a5050,
0xaa550000, 0xaa555500, 0xaaaa5500, 0x90909090,
0x94949494, 0xa4a4a4a4, 0xa9a59450, 0x2a0a4250,
0xa5945040, 0x0a425054, 0xa5a5a500, 0x55a0a0a0,
0xa8a85454, 0x6a6a4040, 0xa4a45000, 0x1a1a0500,
0x0050a4a4, 0xaaa59090, 0x14696914, 0x69691400,
0xa08585a0, 0xaa821414, 0x50a4a450, 0x6a5a0200,
0xa9a58000, 0x5090a0a8, 0xa8a09050, 0x24242424,
0x00aa5500, 0x24924924, 0x24499224, 0x50a50a50,
0x500aa550, 0xaaaa4444, 0x66660000, 0xa5a0a5a0,
0x50a050a0, 0x69286928, 0x44aaaa44, 0x66666600,
0xaa444444, 0x54a854a8, 0x95809580, 0x96969600,
0xa85454a8, 0x80959580, 0xaa141414, 0x96960000,
0xaaaa1414, 0xa05050a0, 0xa0a5a5a0, 0x96000000,
0x40804080, 0xa9a8a9a8, 0xaaaaaa44, 0x2a4a5254};
/* Anchor indices:
Table.A2 */
static const char bc7_ai0[] = {
15,15,15,15,15,15,15,15,
15,15,15,15,15,15,15,15,
15, 2, 8, 2, 2, 8, 8,15,
2, 8, 2, 2, 8, 8, 2, 2,
15,15, 6, 8, 2, 8,15,15,
2, 8, 2, 2, 2,15,15, 6,
6, 2, 6, 8,15,15, 2, 2,
15,15,15,15,15, 2, 2,15};
/* Table.A3a */
static const char bc7_ai1[] = {
3, 3,15,15, 8, 3,15,15,
8, 8, 6, 6, 6, 5, 3, 3,
3, 3, 8,15, 3, 3, 6,10,
5, 8, 8, 6, 8, 5,15,15,
8,15, 3, 5, 6,10, 8,15,
15, 3,15, 5,15,15,15,15,
3,15, 5, 5, 5, 8, 5,10,
5,10, 8,13,15,12, 3, 3};
/* Table.A3b */
static const char bc7_ai2[] = {
15, 8, 8, 3,15,15, 3, 8,
15,15,15,15,15,15,15, 8,
15, 8,15, 3,15, 8,15, 8,
3,15, 6,10,15,15,10, 8,
15, 3,15,10,10, 8, 9,10,
6,15, 8,15, 3, 6, 6, 8,
15, 3,15,15,15,15,15,15,
15,15,15,15, 3,15,15, 8};
/* Interpolation weights */
static const char bc7_weights2[] = {0, 21, 43, 64};
static const char bc7_weights3[] = {0, 9, 18, 27, 37, 46, 55, 64};
static const char bc7_weights4[] = {
0, 4, 9, 13, 17, 21, 26, 30, 34, 38, 43, 47, 51, 55, 60, 64};
static const char *bc7_get_weights(int n) {
if (n == 2) {
return bc7_weights2;
}
if (n == 3) {
return bc7_weights3;
}
return bc7_weights4;
}
static int bc7_get_subset(int ns, int partition, int n) {
if (ns == 2) {
return 1 & (bc7_si2[partition] >> n);
}
if (ns == 3) {
return 3 & (bc7_si3[partition] >> (2 * n));
}
return 0;
}
static UINT8 expand_quantized(UINT8 v, int bits) {
v = v << (8 - bits);
return v | (v >> bits);
}
static void bc7_lerp(rgba *dst, const rgba *e, int s0, int s1) {
int t0 = 64 - s0;
int t1 = 64 - s1;
dst->r = (UINT8)((t0 * e[0].r + s0 * e[1].r + 32) >> 6);
dst->g = (UINT8)((t0 * e[0].g + s0 * e[1].g + 32) >> 6);
dst->b = (UINT8)((t0 * e[0].b + s0 * e[1].b + 32) >> 6);
dst->a = (UINT8)((t1 * e[0].a + s1 * e[1].a + 32) >> 6);
}
static void decode_bc7_block(rgba *col, const UINT8* src) {
rgba endpoints[6];
int bit = 0, cibit, aibit;
int mode = src[0];
int i, j;
int numep, cb, ab, ib, ib2, i0, i1, s;
UINT8 index_sel, partition, rotation, val;
const char *cw, *aw;
const bc7_mode_info *info;
/* mode is the number of unset bits before the first set bit: */
if (!mode) {
/* degenerate case when no bits set */
for (i = 0; i < 16; i++) {
col[i].r = col[i].g = col[i].b = 0;
col[i].a = 255;
}
return;
}
while (!(mode & (1 << bit++))) ;
mode = bit - 1;
info = &bc7_modes[mode];
/* color selection bits: {subset}{endpoint} */
cb = info->cb;
ab = info->ab;
cw = bc7_get_weights(info->ib);
aw = bc7_get_weights((ab && info->ib2) ? info->ib2 : info->ib);
#define LOAD(DST, N) \
DST = get_bits(src, bit, N); \
bit += N;
LOAD(partition, info->pb);
LOAD(rotation, info->rb);
LOAD(index_sel, info->isb);
numep = info->ns << 1;
/* red */
for (i = 0; i < numep; i++) {
LOAD(val, cb);
endpoints[i].r = val;
}
/* green */
for (i = 0; i < numep; i++) {
LOAD(val, cb);
endpoints[i].g = val;
}
/* blue */
for (i = 0; i < numep; i++) {
LOAD(val, cb);
endpoints[i].b = val;
}
/* alpha */
for (i = 0; i < numep; i++) {
if (ab) {
LOAD(val, ab);
} else {
val = 255;
}
endpoints[i].a = val;
}
/* p-bits */
#define ASSIGN_P(x) x = (x << 1) | val
if (info->epb) {
/* per endpoint */
cb++;
if (ab) {
ab++;
}
for (i = 0; i < numep; i++) {
LOAD(val, 1);
ASSIGN_P(endpoints[i].r);
ASSIGN_P(endpoints[i].g);
ASSIGN_P(endpoints[i].b);
if (ab) {
ASSIGN_P(endpoints[i].a);
}
}
}
if (info->spb) {
/* per subset */
cb++;
if (ab) {
ab++;
}
for (i = 0; i < numep; i+=2) {
LOAD(val, 1);
for (j = 0; j < 2; j++) {
ASSIGN_P(endpoints[i+j].r);
ASSIGN_P(endpoints[i+j].g);
ASSIGN_P(endpoints[i+j].b);
if (ab) {
ASSIGN_P(endpoints[i+j].a);
}
}
}
}
#undef ASSIGN_P
#define EXPAND(x, b) x = expand_quantized(x, b)
for (i = 0; i < numep; i++) {
EXPAND(endpoints[i].r, cb);
EXPAND(endpoints[i].g, cb);
EXPAND(endpoints[i].b, cb);
if (ab) {
EXPAND(endpoints[i].a, ab);
}
}
#undef EXPAND
#undef LOAD
cibit = bit;
aibit = cibit + 16 * info->ib - info->ns;
for (i = 0; i < 16; i++) {
s = bc7_get_subset(info->ns, partition, i) << 1;
ib = info->ib;
if (i == 0) {
ib--;
} else if (info->ns == 2) {
if (i == bc7_ai0[partition]) {
ib--;
}
} else if (info->ns == 3) {
if (i == bc7_ai1[partition]) {
ib--;
} else if (i == bc7_ai2[partition]) {
ib--;
}
}
i0 = get_bits(src, cibit, ib);
cibit += ib;
if (ab && info->ib2) {
ib2 = info->ib2;
if (ib2 && i == 0) {
ib2--;
}
i1 = get_bits(src, aibit, ib2);
aibit += ib2;
if (index_sel) {
bc7_lerp(&col[i], &endpoints[s], aw[i1], cw[i0]);
} else {
bc7_lerp(&col[i], &endpoints[s], cw[i0], aw[i1]);
}
} else {
bc7_lerp(&col[i], &endpoints[s], cw[i0], cw[i0]);
}
#define ROTATE(x, y) \
val = x; \
x = y; \
y = val
if (rotation == 1) {
ROTATE(col[i].r, col[i].a);
} else if (rotation == 2) {
ROTATE(col[i].g, col[i].a);
} else if (rotation == 3) {
ROTATE(col[i].b, col[i].a);
}
#undef ROTATE
}
}
/* BC6 */
typedef struct {
char ns; /* number of subsets (also called regions) */
char tr; /* whether endpoints are delta-compressed */
char pb; /* partition bits */
char epb; /* endpoint bits */
char rb; /* red bits (delta) */
char gb; /* green bits (delta) */
char bb; /* blue bits (delta) */
} bc6_mode_info;
static const bc6_mode_info bc6_modes[] = {
// 00
{2, 1, 5, 10, 5, 5, 5},
// 01
{2, 1, 5, 7, 6, 6, 6},
// 10
{2, 1, 5, 11, 5, 4, 4},
{2, 1, 5, 11, 4, 5, 4},
{2, 1, 5, 11, 4, 4, 5},
{2, 1, 5, 9, 5, 5, 5},
{2, 1, 5, 8, 6, 5, 5},
{2, 1, 5, 8, 5, 6, 5},
{2, 1, 5, 8, 5, 5, 6},
{2, 0, 5, 6, 6, 6, 6},
// 11
{1, 0, 0, 10, 10, 10, 10},
{1, 1, 0, 11, 9, 9, 9},
{1, 1, 0, 12, 8, 8, 8},
{1, 1, 0, 16, 4, 4, 4}
};
/* Table.F, encoded as a sequence of bit indices */
static const UINT8 bc6_bit_packings[][75] = {
{116, 132, 176, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 22,
23, 24, 25, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52,
164, 112, 113, 114, 115, 64, 65, 66, 67, 68, 172, 160, 161, 162, 163, 80,
81, 82, 83, 84, 173, 128, 129, 130, 131, 96, 97, 98, 99, 100, 174, 144,
145, 146, 147, 148, 175},
{117, 164, 165, 0, 1, 2, 3, 4, 5, 6, 172, 173, 132, 16, 17, 18, 19, 20, 21,
22, 133, 174, 116, 32, 33, 34, 35, 36, 37, 38, 175, 177, 176, 48, 49, 50,
51, 52, 53, 112, 113, 114, 115, 64, 65, 66, 67, 68, 69, 160, 161, 162, 163,
80, 81, 82, 83, 84, 85, 128, 129, 130, 131, 96, 97, 98, 99, 100, 101, 144,
145, 146, 147, 148, 149},
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 32,
33, 34, 35, 36, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 10, 112, 113, 114,
115, 64, 65, 66, 67, 26, 172, 160, 161, 162, 163, 80, 81, 82, 83, 42, 173,
128, 129, 130, 131, 96, 97, 98, 99, 100, 174, 144, 145, 146, 147, 148,
175},
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 32,
33, 34, 35, 36, 37, 38, 39, 40, 41, 48, 49, 50, 51, 10, 164, 112, 113, 114,
115, 64, 65, 66, 67, 68, 26, 160, 161, 162, 163, 80, 81, 82, 83, 42, 173,
128, 129, 130, 131, 96, 97, 98, 99, 172, 174, 144, 145, 146, 147, 116,
175},
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 32,
33, 34, 35, 36, 37, 38, 39, 40, 41, 48, 49, 50, 51, 10, 132, 112, 113, 114,
115, 64, 65, 66, 67, 26, 172, 160, 161, 162, 163, 80, 81, 82, 83, 84, 42,
128, 129, 130, 131, 96, 97, 98, 99, 173, 174, 144, 145, 146, 147, 176,
175},
{0, 1, 2, 3, 4, 5, 6, 7, 8, 132, 16, 17, 18, 19, 20, 21, 22, 23, 24, 116,
32, 33, 34, 35, 36, 37, 38, 39, 40, 176, 48, 49, 50, 51, 52, 164, 112, 113,
114, 115, 64, 65, 66, 67, 68, 172, 160, 161, 162, 163, 80, 81, 82, 83, 84,
173, 128, 129, 130, 131, 96, 97, 98, 99, 100, 174, 144, 145, 146, 147, 148,
175},
{0, 1, 2, 3, 4, 5, 6, 7, 164, 132, 16, 17, 18, 19, 20, 21, 22, 23, 174, 116,
32, 33, 34, 35, 36, 37, 38, 39, 175, 176, 48, 49, 50, 51, 52, 53, 112, 113,
114, 115, 64, 65, 66, 67, 68, 172, 160, 161, 162, 163, 80, 81, 82, 83, 84,
173, 128, 129, 130, 131, 96, 97, 98, 99, 100, 101, 144, 145, 146, 147, 148,
149},
{0, 1, 2, 3, 4, 5, 6, 7, 172, 132, 16, 17, 18, 19, 20, 21, 22, 23, 117, 116,
32, 33, 34, 35, 36, 37, 38, 39, 165, 176, 48, 49, 50, 51, 52, 164, 112,
113, 114, 115, 64, 65, 66, 67, 68, 69, 160, 161, 162, 163, 80, 81, 82, 83,
84, 173, 128, 129, 130, 131, 96, 97, 98, 99, 100, 174, 144, 145, 146, 147,
148, 175},
{0, 1, 2, 3, 4, 5, 6, 7, 173, 132, 16, 17, 18, 19, 20, 21, 22, 23, 133, 116,
32, 33, 34, 35, 36, 37, 38, 39, 177, 176, 48, 49, 50, 51, 52, 164, 112,
113, 114, 115, 64, 65, 66, 67, 68, 172, 160, 161, 162, 163, 80, 81, 82, 83,
84, 85, 128, 129, 130, 131, 96, 97, 98, 99, 100, 174, 144, 145, 146, 147,
148, 175},
{0, 1, 2, 3, 4, 5, 164, 172, 173, 132, 16, 17, 18, 19, 20, 21, 117, 133,
174, 116, 32, 33, 34, 35, 36, 37, 165, 175, 177, 176, 48, 49, 50, 51, 52,
53, 112, 113, 114, 115, 64, 65, 66, 67, 68, 69, 160, 161, 162, 163, 80, 81,
82, 83, 84, 85, 128, 129, 130, 131, 96, 97, 98, 99, 100, 101, 144, 145,
146, 147, 148, 149},
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 32,
33, 34, 35, 36, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57,
64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 80, 81, 82, 83, 84, 85, 86, 87, 88,
89},
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 32,
33, 34, 35, 36, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 56, 10,
64, 65, 66, 67, 68, 69, 70, 71, 72, 26, 80, 81, 82, 83, 84, 85, 86, 87, 88,
42},
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 32,
33, 34, 35, 36, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 11, 10,
64, 65, 66, 67, 68, 69, 70, 71, 27, 26, 80, 81, 82, 83, 84, 85, 86, 87, 43,
42},
{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 32,
33, 34, 35, 36, 37, 38, 39, 40, 41, 48, 49, 50, 51, 15, 14, 13, 12, 11, 10,
64, 65, 66, 67, 31, 30, 29, 28, 27, 26, 80, 81, 82, 83, 47, 46, 45, 44, 43,
42}};
static void bc6_sign_extend(UINT16 *v, int prec) {
int x = *v;
if (x & (1 << (prec - 1))) {
x |= -1 << prec;
}
*v = (UINT16)x;
}
static int bc6_unquantize(UINT16 v, int prec, int sign) {
int s = 0;
int x;
if (!sign) {
x = v;
if (prec >= 15) return x;
if (x == 0) return 0;
if (x == ((1 << prec) - 1)) {
return 0xffff;
}
return ((x << 15) + 0x4000) >> (prec - 1);
} else {
x = (INT16)v;
if (prec >= 16) return x;
if (x < 0) {
s = 1;
x = -x;
}
if (x != 0) {
if (x >= ((1 << (prec - 1)) - 1)) {
x = 0x7fff;
} else {
x = ((x << 15) + 0x4000) >> (prec - 1);
}
}
if (s) {
return -x;
}
return x;
}
}
static float half_to_float(UINT16 h) {
/* https://gist.github.com/rygorous/2144712 */
union {
UINT32 u;
float f;
} o, m;
m.u = 0x77800000;
o.u = (h & 0x7fff) << 13;
o.f *= m.f;
m.u = 0x47800000;
if (o.f >= m.f) {
o.u |= 255 << 23;
}
o.u |= (h & 0x8000) << 16;
return o.f;
}
static float bc6_finalize(int v, int sign) {
if (sign) {
if (v < 0) {
v = ((-v) * 31) / 32;
return half_to_float((UINT16)(0x8000 | v));
} else {
return half_to_float((UINT16)((v * 31) / 32));
}
} else {
return half_to_float((UINT16)((v * 31) / 64));
}
}
static void bc6_lerp(rgb32f *col, int *e0, int *e1, int s, int sign) {
int r, g, b;
int t = 64 - s;
r = (e0[0] * t + e1[0] * s) >> 6;
g = (e0[1] * t + e1[1] * s) >> 6;
b = (e0[2] * t + e1[2] * s) >> 6;
col->r = bc6_finalize(r, sign);
col->g = bc6_finalize(g, sign);
col->b = bc6_finalize(b, sign);
}
static void decode_bc6_block(rgb32f *col, const UINT8* src, int sign) {
UINT16 endpoints[12]; /* storage for r0, g0, b0, r1, ... */
int ueps[12];
int i, i0, ib2, di, dw, mask, numep, s;
UINT8 partition;
const bc6_mode_info *info;
const char *cw;
int bit = 5;
int epbits = 75;
int ib = 3;
int mode = src[0] & 0x1f;
if ((mode & 3) == 0 || (mode & 3) == 1) {
mode &= 3;
bit = 2;
} else if ((mode & 3) == 2) {
mode = 2 + (mode >> 2);
epbits = 72;
} else {
mode = 10 + (mode >> 2);
epbits = 60;
ib = 4;
}
if (mode >= 14) {
/* invalid block */
memset(col, 0, 16 * sizeof(col[0]));
return;
}
info = &bc6_modes[mode];
cw = bc7_get_weights(ib);
numep = info->ns == 2 ? 12 : 6;
for (i = 0; i < 12; i++) {
endpoints[i] = 0;
}
for (i = 0; i < epbits; i++) {
di = bc6_bit_packings[mode][i];
dw = di >> 4;
di &= 15;
endpoints[dw] |= (UINT16)get_bit(src, bit + i) << di;
}
bit += epbits;
partition = get_bits(src, bit, info->pb);
bit += info->pb;
mask = (1 << info->epb) - 1;
if (sign) { /* sign-extend e0 if signed */
bc6_sign_extend(&endpoints[0], info->epb);
bc6_sign_extend(&endpoints[1], info->epb);
bc6_sign_extend(&endpoints[2], info->epb);
}
if (sign || info->tr) { /* sign-extend e1,2,3 if signed or deltas */
for (i = 3; i < numep; i += 3) {
bc6_sign_extend(&endpoints[i+0], info->rb);
bc6_sign_extend(&endpoints[i+1], info->gb);
bc6_sign_extend(&endpoints[i+2], info->bb);
}
}
if (info->tr) { /* apply deltas */
for (i = 3; i < numep; i++) {
endpoints[i] = (endpoints[i] + endpoints[0]) & mask;
}
if (sign) {
for (i = 3; i < numep; i += 3) {
bc6_sign_extend(&endpoints[i+0], info->rb);
bc6_sign_extend(&endpoints[i+1], info->gb);
bc6_sign_extend(&endpoints[i+2], info->bb);
}
}
}
for (i = 0; i < numep; i++) {
ueps[i] = bc6_unquantize(endpoints[i], info->epb, sign);
}
for (i = 0; i < 16; i++) {
s = bc7_get_subset(info->ns, partition, i) * 6;
ib2 = ib;
if (i == 0) {
ib2--;
} else if (info->ns == 2) {
if (i == bc7_ai0[partition]) {
ib2--;
}
}
i0 = get_bits(src, bit, ib2);
bit += ib2;
bc6_lerp(&col[i], &ueps[s], &ueps[s+3], cw[i0], sign);
}
}
static void put_block(Imaging im, ImagingCodecState state, const char *col, int sz, int C) {
int width = state->xsize;
int height = state->ysize;
int xmax = width + state->xoff;
int ymax = height + state->yoff;
int j, i, y, x;
char *dst;
for (j = 0; j < 4; j++) {
y = state->y + j;
if (C) {
if (y >= height) {
continue;
}
if (state->ystep < 0) {
y = state->yoff + ymax - y - 1;
}
dst = im->image[y];
for (i = 0; i < 4; i++) {
x = state->x + i;
if (x >= width) {
continue;
}
memcpy(dst + sz*x, col + sz*(j*4 + i), sz);
}
} else {
if (state->ystep < 0) {
y = state->yoff + ymax - y - 1;
}
x = state->x;
dst = im->image[y] + sz*x;
memcpy(dst, col + sz*(j*4), 4 * sz);
}
}
state->x += 4;
if (state->x >= xmax) {
state->y += 4;
state->x = state->xoff;
}
}
static int decode_bcn(Imaging im, ImagingCodecState state, const UINT8* src, int bytes, int N, int C) {
int ymax = state->ysize + state->yoff;
const UINT8 *ptr = src;
switch (N) {
#define DECODE_LOOP(NN, SZ, TY, ...) \
case NN: \
while (bytes >= SZ) { \
TY col[16]; \
decode_bc##NN##_block(col, ptr); \
put_block(im, state, (const char *)col, sizeof(col[0]), C); \
ptr += SZ; \
bytes -= SZ; \
if (state->y >= ymax) return -1; \
} \
break
DECODE_LOOP(1, 8, rgba);
DECODE_LOOP(2, 16, rgba);
DECODE_LOOP(3, 16, rgba);
DECODE_LOOP(4, 8, lum);
DECODE_LOOP(5, 16, rgba);
case 6:
while (bytes >= 16) {
rgb32f col[16];
decode_bc6_block(col, ptr, (state->state >> 4) & 1);
put_block(im, state, (const char *)col, sizeof(col[0]), C);
ptr += 16;
bytes -= 16;
if (state->y >= ymax) return -1; \
}
break;
DECODE_LOOP(7, 16, rgba);
#undef DECODE_LOOP
}
return (int)(ptr - src);
}
int ImagingBcnDecode(Imaging im, ImagingCodecState state, UINT8* buf, int bytes) {
int N = state->state & 0xf;
int width = state->xsize;
int height = state->ysize;
if ((width & 3) | (height & 3)) {
return decode_bcn(im, state, buf, bytes, N, 1);
} else {
return decode_bcn(im, state, buf, bytes, N, 0);
}
}