1/*
2 * Copyright 2013 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#include "SkMipMap.h"
9#include "SkBitmap.h"
10#include "SkColorPriv.h"
11
12static void downsampleby2_proc32(SkBitmap* dst, int x, int y,
13                                 const SkBitmap& src) {
14    x <<= 1;
15    y <<= 1;
16    const SkPMColor* p = src.getAddr32(x, y);
17    const SkPMColor* baseP = p;
18    SkPMColor c, ag, rb;
19
20    c = *p; ag = (c >> 8) & 0xFF00FF; rb = c & 0xFF00FF;
21    if (x < src.width() - 1) {
22        p += 1;
23    }
24    c = *p; ag += (c >> 8) & 0xFF00FF; rb += c & 0xFF00FF;
25
26    p = baseP;
27    if (y < src.height() - 1) {
28        p += src.rowBytes() >> 2;
29    }
30    c = *p; ag += (c >> 8) & 0xFF00FF; rb += c & 0xFF00FF;
31    if (x < src.width() - 1) {
32        p += 1;
33    }
34    c = *p; ag += (c >> 8) & 0xFF00FF; rb += c & 0xFF00FF;
35
36    *dst->getAddr32(x >> 1, y >> 1) =
37    ((rb >> 2) & 0xFF00FF) | ((ag << 6) & 0xFF00FF00);
38}
39
40static inline uint32_t expand16(U16CPU c) {
41    return (c & ~SK_G16_MASK_IN_PLACE) | ((c & SK_G16_MASK_IN_PLACE) << 16);
42}
43
44// returns dirt in the top 16bits, but we don't care, since we only
45// store the low 16bits.
46static inline U16CPU pack16(uint32_t c) {
47    return (c & ~SK_G16_MASK_IN_PLACE) | ((c >> 16) & SK_G16_MASK_IN_PLACE);
48}
49
50static void downsampleby2_proc16(SkBitmap* dst, int x, int y,
51                                 const SkBitmap& src) {
52    x <<= 1;
53    y <<= 1;
54    const uint16_t* p = src.getAddr16(x, y);
55    const uint16_t* baseP = p;
56    SkPMColor       c;
57
58    c = expand16(*p);
59    if (x < src.width() - 1) {
60        p += 1;
61    }
62    c += expand16(*p);
63
64    p = baseP;
65    if (y < src.height() - 1) {
66        p += src.rowBytes() >> 1;
67    }
68    c += expand16(*p);
69    if (x < src.width() - 1) {
70        p += 1;
71    }
72    c += expand16(*p);
73
74    *dst->getAddr16(x >> 1, y >> 1) = (uint16_t)pack16(c >> 2);
75}
76
77static uint32_t expand4444(U16CPU c) {
78    return (c & 0xF0F) | ((c & ~0xF0F) << 12);
79}
80
81static U16CPU collaps4444(uint32_t c) {
82    return (c & 0xF0F) | ((c >> 12) & ~0xF0F);
83}
84
85static void downsampleby2_proc4444(SkBitmap* dst, int x, int y,
86                                   const SkBitmap& src) {
87    x <<= 1;
88    y <<= 1;
89    const uint16_t* p = src.getAddr16(x, y);
90    const uint16_t* baseP = p;
91    uint32_t        c;
92
93    c = expand4444(*p);
94    if (x < src.width() - 1) {
95        p += 1;
96    }
97    c += expand4444(*p);
98
99    p = baseP;
100    if (y < src.height() - 1) {
101        p += src.rowBytes() >> 1;
102    }
103    c += expand4444(*p);
104    if (x < src.width() - 1) {
105        p += 1;
106    }
107    c += expand4444(*p);
108
109    *dst->getAddr16(x >> 1, y >> 1) = (uint16_t)collaps4444(c >> 2);
110}
111
112SkMipMap::Level* SkMipMap::AllocLevels(int levelCount, size_t pixelSize) {
113    if (levelCount < 0) {
114        return NULL;
115    }
116    int64_t size = sk_64_mul(levelCount + 1, sizeof(Level)) + pixelSize;
117    if (!sk_64_isS32(size)) {
118        return NULL;
119    }
120    return (Level*)sk_malloc_throw(sk_64_asS32(size));
121}
122
123SkMipMap* SkMipMap::Build(const SkBitmap& src) {
124    void (*proc)(SkBitmap* dst, int x, int y, const SkBitmap& src);
125
126    const SkColorType ct = src.colorType();
127    const SkAlphaType at = src.alphaType();
128    switch (ct) {
129        case kRGBA_8888_SkColorType:
130        case kBGRA_8888_SkColorType:
131            proc = downsampleby2_proc32;
132            break;
133        case kRGB_565_SkColorType:
134            proc = downsampleby2_proc16;
135            break;
136        case kARGB_4444_SkColorType:
137            proc = downsampleby2_proc4444;
138            break;
139        default:
140            return NULL; // don't build mipmaps for any other colortypes (yet)
141    }
142
143    SkAutoLockPixels alp(src);
144    if (!src.readyToDraw()) {
145        return NULL;
146    }
147
148    // whip through our loop to compute the exact size needed
149    size_t  size = 0;
150    int     countLevels = 0;
151    {
152        int width = src.width();
153        int height = src.height();
154        for (;;) {
155            width >>= 1;
156            height >>= 1;
157            if (0 == width || 0 == height) {
158                break;
159            }
160            size += SkColorTypeMinRowBytes(ct, width) * height;
161            countLevels += 1;
162        }
163    }
164    if (0 == countLevels) {
165        return NULL;
166    }
167
168    Level* levels = SkMipMap::AllocLevels(countLevels, size);
169    if (NULL == levels) {
170        return NULL;
171    }
172
173    uint8_t*    baseAddr = (uint8_t*)&levels[countLevels];
174    uint8_t*    addr = baseAddr;
175    int         width = src.width();
176    int         height = src.height();
177    uint32_t    rowBytes;
178    SkBitmap    srcBM(src);
179
180    for (int i = 0; i < countLevels; ++i) {
181        width >>= 1;
182        height >>= 1;
183        rowBytes = SkToU32(SkColorTypeMinRowBytes(ct, width));
184
185        levels[i].fPixels   = addr;
186        levels[i].fWidth    = width;
187        levels[i].fHeight   = height;
188        levels[i].fRowBytes = rowBytes;
189        levels[i].fScale    = (float)width / src.width();
190
191        SkBitmap dstBM;
192        dstBM.installPixels(SkImageInfo::Make(width, height, ct, at), addr, rowBytes);
193
194        srcBM.lockPixels();
195        for (int y = 0; y < height; y++) {
196            for (int x = 0; x < width; x++) {
197                proc(&dstBM, x, y, srcBM);
198            }
199        }
200        srcBM.unlockPixels();
201
202        srcBM = dstBM;
203        addr += height * rowBytes;
204    }
205    SkASSERT(addr == baseAddr + size);
206
207    return SkNEW_ARGS(SkMipMap, (levels, countLevels, size));
208}
209
210///////////////////////////////////////////////////////////////////////////////
211
212//static int gCounter;
213
214SkMipMap::SkMipMap(Level* levels, int count, size_t size)
215    : fSize(size), fLevels(levels), fCount(count) {
216    SkASSERT(levels);
217    SkASSERT(count > 0);
218//    SkDebugf("mips %d\n", ++gCounter);
219}
220
221SkMipMap::~SkMipMap() {
222    sk_free(fLevels);
223//    SkDebugf("mips %d\n", --gCounter);
224}
225
226static SkFixed compute_level(SkScalar scale) {
227    SkFixed s = SkAbs32(SkScalarToFixed(SkScalarInvert(scale)));
228
229    if (s < SK_Fixed1) {
230        return 0;
231    }
232    int clz = SkCLZ(s);
233    SkASSERT(clz >= 1 && clz <= 15);
234    return SkIntToFixed(15 - clz) + ((unsigned)(s << (clz + 1)) >> 16);
235}
236
237bool SkMipMap::extractLevel(SkScalar scale, Level* levelPtr) const {
238    if (scale >= SK_Scalar1) {
239        return false;
240    }
241
242    int level = compute_level(scale) >> 16;
243    SkASSERT(level >= 0);
244    if (level <= 0) {
245        return false;
246    }
247
248    if (level > fCount) {
249        level = fCount;
250    }
251    if (levelPtr) {
252        *levelPtr = fLevels[level - 1];
253    }
254    return true;
255}
256