SkMipMap.cpp revision 92561a0b99ad6c08ab7a11dd1872f028199392e9 
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
112size_t SkMipMap::AllocLevelsSize(int levelCount, size_t pixelSize) {
113    if (levelCount < 0) {
114        return 0;
115    }
116    int64_t size = sk_64_mul(levelCount + 1, sizeof(Level)) + pixelSize;
117    if (!sk_64_isS32(size)) {
118        return 0;
119    }
120    return sk_64_asS32(size);
121}
122
123SkMipMap* SkMipMap::Build(const SkBitmap& src, SkDiscardableFactoryProc fact) {
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    size_t storageSize = SkMipMap::AllocLevelsSize(countLevels, size);
169    if (0 == storageSize) {
170        return NULL;
171    }
172
173    SkMipMap* mipmap;
174    if (fact) {
175        SkDiscardableMemory* dm = fact(storageSize);
176        if (NULL == dm) {
177            return NULL;
178        }
179        mipmap = SkNEW_ARGS(SkMipMap, (storageSize, dm));
180    } else {
181        mipmap = SkNEW_ARGS(SkMipMap, (sk_malloc_throw(storageSize), storageSize));
182    }
183
184    // init
185    mipmap->fCount = countLevels;
186    mipmap->fLevels = (Level*)mipmap->writable_data();
187
188    Level* levels = mipmap->fLevels;
189    uint8_t*    baseAddr = (uint8_t*)&levels[countLevels];
190    uint8_t*    addr = baseAddr;
191    int         width = src.width();
192    int         height = src.height();
193    uint32_t    rowBytes;
194    SkBitmap    srcBM(src);
195
196    for (int i = 0; i < countLevels; ++i) {
197        width >>= 1;
198        height >>= 1;
199        rowBytes = SkToU32(SkColorTypeMinRowBytes(ct, width));
200
201        levels[i].fPixels   = addr;
202        levels[i].fWidth    = width;
203        levels[i].fHeight   = height;
204        levels[i].fRowBytes = rowBytes;
205        levels[i].fScale    = (float)width / src.width();
206
207        SkBitmap dstBM;
208        dstBM.installPixels(SkImageInfo::Make(width, height, ct, at), addr, rowBytes);
209
210        srcBM.lockPixels();
211        for (int y = 0; y < height; y++) {
212            for (int x = 0; x < width; x++) {
213                proc(&dstBM, x, y, srcBM);
214            }
215        }
216        srcBM.unlockPixels();
217
218        srcBM = dstBM;
219        addr += height * rowBytes;
220    }
221    SkASSERT(addr == baseAddr + size);
222
223    return mipmap;
224}
225
226///////////////////////////////////////////////////////////////////////////////
227
228//static int gCounter;
229
230static SkFixed compute_level(SkScalar scale) {
231    SkFixed s = SkAbs32(SkScalarToFixed(SkScalarInvert(scale)));
232
233    if (s < SK_Fixed1) {
234        return 0;
235    }
236    int clz = SkCLZ(s);
237    SkASSERT(clz >= 1 && clz <= 15);
238    return SkIntToFixed(15 - clz) + ((unsigned)(s << (clz + 1)) >> 16);
239}
240
241bool SkMipMap::extractLevel(SkScalar scale, Level* levelPtr) const {
242    if (NULL == fLevels) {
243        return false;
244    }
245
246    if (scale >= SK_Scalar1) {
247        return false;
248    }
249
250    int level = compute_level(scale) >> 16;
251    SkASSERT(level >= 0);
252    if (level <= 0) {
253        return false;
254    }
255
256    if (level > fCount) {
257        level = fCount;
258    }
259    if (levelPtr) {
260        *levelPtr = fLevels[level - 1];
261    }
262    return true;
263}
264