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1 #include "SkBitmapProcState.h"
2 #include "SkBitmapProcState_filter.h"
3 #include "SkColorPriv.h"
4 #include "SkFilterProc.h"
5 #include "SkPaint.h"
6 #include "SkShader.h"   // for tilemodes
7 
8 // returns expanded * 5bits
Filter_565_Expanded(unsigned x,unsigned y,uint32_t a00,uint32_t a01,uint32_t a10,uint32_t a11)9 static inline uint32_t Filter_565_Expanded(unsigned x, unsigned y,
10                                            uint32_t a00, uint32_t a01,
11                                            uint32_t a10, uint32_t a11) {
12     SkASSERT((unsigned)x <= 0xF);
13     SkASSERT((unsigned)y <= 0xF);
14 
15     a00 = SkExpand_rgb_16(a00);
16     a01 = SkExpand_rgb_16(a01);
17     a10 = SkExpand_rgb_16(a10);
18     a11 = SkExpand_rgb_16(a11);
19 
20     int xy = x * y >> 3;
21     return  a00 * (32 - 2*y - 2*x + xy) +
22             a01 * (2*x - xy) +
23             a10 * (2*y - xy) +
24             a11 * xy;
25 }
26 
27 // turn an expanded 565 * 5bits into SkPMColor
28 // g:11 | r:10 | x:1 | b:10
SkExpanded_565_To_PMColor(uint32_t c)29 static inline SkPMColor SkExpanded_565_To_PMColor(uint32_t c) {
30     unsigned r = (c >> 13) & 0xFF;
31     unsigned g = (c >> 24);
32     unsigned b = (c >> 2) & 0xFF;
33     return SkPackARGB32(0xFF, r, g, b);
34 }
35 
36 // returns answer in SkPMColor format
Filter_4444_D32(unsigned x,unsigned y,uint32_t a00,uint32_t a01,uint32_t a10,uint32_t a11)37 static inline SkPMColor Filter_4444_D32(unsigned x, unsigned y,
38                                         uint32_t a00, uint32_t a01,
39                                         uint32_t a10, uint32_t a11) {
40     SkASSERT((unsigned)x <= 0xF);
41     SkASSERT((unsigned)y <= 0xF);
42 
43     a00 = SkExpand_4444(a00);
44     a01 = SkExpand_4444(a01);
45     a10 = SkExpand_4444(a10);
46     a11 = SkExpand_4444(a11);
47 
48     int xy = x * y >> 4;
49     uint32_t result =   a00 * (16 - y - x + xy) +
50                         a01 * (x - xy) +
51                         a10 * (y - xy) +
52                         a11 * xy;
53 
54     return SkCompact_8888(result);
55 }
56 
Filter_8(unsigned x,unsigned y,U8CPU a00,U8CPU a01,U8CPU a10,U8CPU a11)57 static inline U8CPU Filter_8(unsigned x, unsigned y,
58                              U8CPU a00, U8CPU a01,
59                              U8CPU a10, U8CPU a11) {
60     SkASSERT((unsigned)x <= 0xF);
61     SkASSERT((unsigned)y <= 0xF);
62 
63     int xy = x * y;
64     unsigned result =   a00 * (256 - 16*y - 16*x + xy) +
65                         a01 * (16*x - xy) +
66                         a10 * (16*y - xy) +
67                         a11 * xy;
68 
69     return result >> 8;
70 }
71 
72 /*****************************************************************************
73  *
74  *  D32 functions
75  *
76  */
77 
78 // SRC == 8888
79 
80 #define FILTER_PROC(x, y, a, b, c, d, dst)   Filter_32_opaque(x, y, a, b, c, d, dst)
81 
82 #define MAKENAME(suffix)        S32_opaque_D32 ## suffix
83 #define DSTSIZE                 32
84 #define SRCTYPE                 SkPMColor
85 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kARGB_8888_Config); \
86                                 SkASSERT(state.fAlphaScale == 256)
87 #define RETURNDST(src)          src
88 #define SRC_TO_FILTER(src)      src
89 #include "SkBitmapProcState_sample.h"
90 
91 #undef FILTER_PROC
92 #define FILTER_PROC(x, y, a, b, c, d, dst)   Filter_32_alpha(x, y, a, b, c, d, dst, alphaScale)
93 
94 #define MAKENAME(suffix)        S32_alpha_D32 ## suffix
95 #define DSTSIZE                 32
96 #define SRCTYPE                 SkPMColor
97 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kARGB_8888_Config); \
98                                 SkASSERT(state.fAlphaScale < 256)
99 #define PREAMBLE(state)         unsigned alphaScale = state.fAlphaScale
100 #define RETURNDST(src)          SkAlphaMulQ(src, alphaScale)
101 #define SRC_TO_FILTER(src)      src
102 #include "SkBitmapProcState_sample.h"
103 
104 // SRC == 565
105 
106 #undef FILTER_PROC
107 #define FILTER_PROC(x, y, a, b, c, d, dst) \
108     do {                                                        \
109         uint32_t tmp = Filter_565_Expanded(x, y, a, b, c, d);   \
110         *(dst) = SkExpanded_565_To_PMColor(tmp);                \
111     } while (0)
112 
113 #define MAKENAME(suffix)        S16_opaque_D32 ## suffix
114 #define DSTSIZE                 32
115 #define SRCTYPE                 uint16_t
116 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kRGB_565_Config); \
117                                 SkASSERT(state.fAlphaScale == 256)
118 #define RETURNDST(src)          SkPixel16ToPixel32(src)
119 #define SRC_TO_FILTER(src)      src
120 #include "SkBitmapProcState_sample.h"
121 
122 #undef FILTER_PROC
123 #define FILTER_PROC(x, y, a, b, c, d, dst) \
124     do {                                                                    \
125         uint32_t tmp = Filter_565_Expanded(x, y, a, b, c, d);               \
126         *(dst) = SkAlphaMulQ(SkExpanded_565_To_PMColor(tmp), alphaScale);   \
127     } while (0)
128 
129 #define MAKENAME(suffix)        S16_alpha_D32 ## suffix
130 #define DSTSIZE                 32
131 #define SRCTYPE                 uint16_t
132 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kRGB_565_Config); \
133                                 SkASSERT(state.fAlphaScale < 256)
134 #define PREAMBLE(state)         unsigned alphaScale = state.fAlphaScale
135 #define RETURNDST(src)          SkAlphaMulQ(SkPixel16ToPixel32(src), alphaScale)
136 #define SRC_TO_FILTER(src)      src
137 #include "SkBitmapProcState_sample.h"
138 
139 // SRC == Index8
140 
141 #undef FILTER_PROC
142 #define FILTER_PROC(x, y, a, b, c, d, dst)   Filter_32_opaque(x, y, a, b, c, d, dst)
143 
144 #define MAKENAME(suffix)        SI8_opaque_D32 ## suffix
145 #define DSTSIZE                 32
146 #define SRCTYPE                 uint8_t
147 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kIndex8_Config); \
148                                 SkASSERT(state.fAlphaScale == 256)
149 #define PREAMBLE(state)         const SkPMColor* SK_RESTRICT table = state.fBitmap->getColorTable()->lockColors()
150 #define RETURNDST(src)          table[src]
151 #define SRC_TO_FILTER(src)      table[src]
152 #define POSTAMBLE(state)        state.fBitmap->getColorTable()->unlockColors(false)
153 #include "SkBitmapProcState_sample.h"
154 
155 #undef FILTER_PROC
156 #define FILTER_PROC(x, y, a, b, c, d, dst)   Filter_32_alpha(x, y, a, b, c, d, dst, alphaScale)
157 
158 #define MAKENAME(suffix)        SI8_alpha_D32 ## suffix
159 #define DSTSIZE                 32
160 #define SRCTYPE                 uint8_t
161 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kIndex8_Config); \
162                                 SkASSERT(state.fAlphaScale < 256)
163 #define PREAMBLE(state)         unsigned alphaScale = state.fAlphaScale; \
164                                 const SkPMColor* SK_RESTRICT table = state.fBitmap->getColorTable()->lockColors()
165 #define RETURNDST(src)          SkAlphaMulQ(table[src], alphaScale)
166 #define SRC_TO_FILTER(src)      table[src]
167 #define POSTAMBLE(state)        state.fBitmap->getColorTable()->unlockColors(false)
168 #include "SkBitmapProcState_sample.h"
169 
170 // SRC == 4444
171 
172 #undef FILTER_PROC
173 #define FILTER_PROC(x, y, a, b, c, d, dst)  *(dst) = Filter_4444_D32(x, y, a, b, c, d)
174 
175 #define MAKENAME(suffix)        S4444_opaque_D32 ## suffix
176 #define DSTSIZE                 32
177 #define SRCTYPE                 SkPMColor16
178 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kARGB_4444_Config); \
179                                 SkASSERT(state.fAlphaScale == 256)
180 #define RETURNDST(src)          SkPixel4444ToPixel32(src)
181 #define SRC_TO_FILTER(src)      src
182 #include "SkBitmapProcState_sample.h"
183 
184 #undef FILTER_PROC
185 #define FILTER_PROC(x, y, a, b, c, d, dst)  \
186     do {                                                    \
187         uint32_t tmp = Filter_4444_D32(x, y, a, b, c, d);   \
188         *(dst) = SkAlphaMulQ(tmp, alphaScale);              \
189     } while (0)
190 
191 #define MAKENAME(suffix)        S4444_alpha_D32 ## suffix
192 #define DSTSIZE                 32
193 #define SRCTYPE                 SkPMColor16
194 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kARGB_4444_Config); \
195                                 SkASSERT(state.fAlphaScale < 256)
196 #define PREAMBLE(state)         unsigned alphaScale = state.fAlphaScale
197 #define RETURNDST(src)          SkAlphaMulQ(SkPixel4444ToPixel32(src), alphaScale)
198 #define SRC_TO_FILTER(src)      src
199 #include "SkBitmapProcState_sample.h"
200 
201 // SRC == A8
202 
203 #undef FILTER_PROC
204 #define FILTER_PROC(x, y, a, b, c, d, dst) \
205     do {                                                        \
206         unsigned tmp = Filter_8(x, y, a, b, c, d);              \
207         *(dst) = SkAlphaMulQ(pmColor, SkAlpha255To256(tmp));    \
208     } while (0)
209 
210 #define MAKENAME(suffix)        SA8_alpha_D32 ## suffix
211 #define DSTSIZE                 32
212 #define SRCTYPE                 uint8_t
213 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kA8_Config); \
214                                 SkASSERT(state.fAlphaScale == 256)
215 #define PREAMBLE(state)         const SkPMColor pmColor = state.fPaintPMColor;
216 #define RETURNDST(src)          SkAlphaMulQ(pmColor, SkAlpha255To256(src))
217 #define SRC_TO_FILTER(src)      src
218 #include "SkBitmapProcState_sample.h"
219 
220 /*****************************************************************************
221  *
222  *  D16 functions
223  *
224  */
225 
226 // SRC == 8888
227 
228 #undef FILTER_PROC
229 #define FILTER_PROC(x, y, a, b, c, d, dst) \
230     do {                                                \
231         SkPMColor dstColor;                             \
232         Filter_32_opaque(x, y, a, b, c, d, &dstColor);  \
233         (*dst) = SkPixel32ToPixel16(dstColor);          \
234     } while (0)
235 
236 #define MAKENAME(suffix)        S32_D16 ## suffix
237 #define DSTSIZE                 16
238 #define SRCTYPE                 SkPMColor
239 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kARGB_8888_Config); \
240                                 SkASSERT(state.fBitmap->isOpaque())
241 #define RETURNDST(src)          SkPixel32ToPixel16(src)
242 #define SRC_TO_FILTER(src)      src
243 #include "SkBitmapProcState_sample.h"
244 
245 // SRC == 565
246 
247 #undef FILTER_PROC
248 #define FILTER_PROC(x, y, a, b, c, d, dst) \
249     do {                                                        \
250         uint32_t tmp = Filter_565_Expanded(x, y, a, b, c, d);   \
251         *(dst) = SkCompact_rgb_16((tmp) >> 5);                  \
252     } while (0)
253 
254 #define MAKENAME(suffix)        S16_D16 ## suffix
255 #define DSTSIZE                 16
256 #define SRCTYPE                 uint16_t
257 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kRGB_565_Config)
258 #define RETURNDST(src)          src
259 #define SRC_TO_FILTER(src)      src
260 #include "SkBitmapProcState_sample.h"
261 
262 // SRC == Index8
263 
264 #undef FILTER_PROC
265 #define FILTER_PROC(x, y, a, b, c, d, dst) \
266     do {                                                        \
267         uint32_t tmp = Filter_565_Expanded(x, y, a, b, c, d);   \
268         *(dst) = SkCompact_rgb_16((tmp) >> 5);                  \
269     } while (0)
270 
271 #define MAKENAME(suffix)        SI8_D16 ## suffix
272 #define DSTSIZE                 16
273 #define SRCTYPE                 uint8_t
274 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kIndex8_Config); \
275                                 SkASSERT(state.fBitmap->isOpaque())
276 #define PREAMBLE(state)         const uint16_t* SK_RESTRICT table = state.fBitmap->getColorTable()->lock16BitCache()
277 #define RETURNDST(src)          table[src]
278 #define SRC_TO_FILTER(src)      table[src]
279 #define POSTAMBLE(state)        state.fBitmap->getColorTable()->unlock16BitCache()
280 #include "SkBitmapProcState_sample.h"
281 
282 ///////////////////////////////////////////////////////////////////////////////
283 
284 #undef FILTER_PROC
285 #define FILTER_PROC(x, y, a, b, c, d, dst) \
286     do {                                                        \
287         uint32_t tmp = Filter_565_Expanded(x, y, a, b, c, d);   \
288         *(dst) = SkCompact_rgb_16((tmp) >> 5);                  \
289     } while (0)
290 
291 
292 #define TILEX_PROCF(fx, max)    SkClampMax((fx) >> 16, max)
293 #define TILEY_PROCF(fy, max)    SkClampMax((fy) >> 16, max)
294 #define TILEX_LOW_BITS(fx, max) (((fx) >> 12) & 0xF)
295 #define TILEY_LOW_BITS(fy, max) (((fy) >> 12) & 0xF)
296 
297 #define MAKENAME(suffix)        Clamp_S16_D16 ## suffix
298 #define SRCTYPE                 uint16_t
299 #define DSTTYPE                 uint16_t
300 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kRGB_565_Config)
301 #define SRC_TO_FILTER(src)      src
302 #include "SkBitmapProcState_shaderproc.h"
303 
304 
305 #define TILEX_PROCF(fx, max)    (((fx) & 0xFFFF) * ((max) + 1) >> 16)
306 #define TILEY_PROCF(fy, max)    (((fy) & 0xFFFF) * ((max) + 1) >> 16)
307 #define TILEX_LOW_BITS(fx, max) ((((fx) & 0xFFFF) * ((max) + 1) >> 12) & 0xF)
308 #define TILEY_LOW_BITS(fy, max) ((((fy) & 0xFFFF) * ((max) + 1) >> 12) & 0xF)
309 
310 #define MAKENAME(suffix)        Repeat_S16_D16 ## suffix
311 #define SRCTYPE                 uint16_t
312 #define DSTTYPE                 uint16_t
313 #define CHECKSTATE(state)       SkASSERT(state.fBitmap->config() == SkBitmap::kRGB_565_Config)
314 #define SRC_TO_FILTER(src)      src
315 #include "SkBitmapProcState_shaderproc.h"
316 
317 ///////////////////////////////////////////////////////////////////////////////
318 
valid_for_filtering(unsigned dimension)319 static bool valid_for_filtering(unsigned dimension) {
320     // for filtering, width and height must fit in 14bits, since we use steal
321     // 2 bits from each to store our 4bit subpixel data
322     return (dimension & ~0x3FFF) == 0;
323 }
324 
chooseProcs(const SkMatrix & inv,const SkPaint & paint)325 bool SkBitmapProcState::chooseProcs(const SkMatrix& inv, const SkPaint& paint) {
326     if (fOrigBitmap.width() == 0 || fOrigBitmap.height() == 0) {
327         return false;
328     }
329 
330     const SkMatrix* m;
331     bool trivial_matrix = (inv.getType() & ~SkMatrix::kTranslate_Mask) == 0;
332     bool clamp_clamp = SkShader::kClamp_TileMode == fTileModeX &&
333                        SkShader::kClamp_TileMode == fTileModeY;
334 
335     if (clamp_clamp || trivial_matrix) {
336         m = &inv;
337     } else {
338         fUnitInvMatrix = inv;
339         fUnitInvMatrix.postIDiv(fOrigBitmap.width(), fOrigBitmap.height());
340         m = &fUnitInvMatrix;
341     }
342 
343     fBitmap = &fOrigBitmap;
344     if (fOrigBitmap.hasMipMap()) {
345         int shift = fOrigBitmap.extractMipLevel(&fMipBitmap,
346                                                 SkScalarToFixed(m->getScaleX()),
347                                                 SkScalarToFixed(m->getSkewY()));
348 
349         if (shift > 0) {
350             if (m != &fUnitInvMatrix) {
351                 fUnitInvMatrix = *m;
352                 m = &fUnitInvMatrix;
353             }
354 
355             SkScalar scale = SkFixedToScalar(SK_Fixed1 >> shift);
356             fUnitInvMatrix.postScale(scale, scale);
357 
358             // now point here instead of fOrigBitmap
359             fBitmap = &fMipBitmap;
360         }
361     }
362 
363     fInvMatrix      = m;
364     fInvProc        = m->getMapXYProc();
365     fInvType        = m->getType();
366     fInvSx          = SkScalarToFixed(m->getScaleX());
367     fInvKy          = SkScalarToFixed(m->getSkewY());
368 
369     fAlphaScale = SkAlpha255To256(paint.getAlpha());
370 
371     // pick-up filtering from the paint, but only if the matrix is
372     // more complex than identity/translate (i.e. no need to pay the cost
373     // of filtering if we're not scaled etc.).
374     // note: we explicitly check inv, since m might be scaled due to unitinv
375     //       trickery, but we don't want to see that for this test
376     fDoFilter = paint.isFilterBitmap() &&
377                 (inv.getType() > SkMatrix::kTranslate_Mask &&
378                  valid_for_filtering(fBitmap->width() | fBitmap->height()));
379 
380     fShaderProc32 = NULL;
381     fShaderProc16 = NULL;
382     fSampleProc32 = NULL;
383     fSampleProc16 = NULL;
384 
385     fMatrixProc = this->chooseMatrixProc(trivial_matrix);
386     if (NULL == fMatrixProc) {
387         return false;
388     }
389 
390     ///////////////////////////////////////////////////////////////////////
391 
392     int index = 0;
393     if (fAlphaScale < 256) {  // note: this distinction is not used for D16
394         index |= 1;
395     }
396     if (fInvType <= (SkMatrix::kTranslate_Mask | SkMatrix::kScale_Mask)) {
397         index |= 2;
398     }
399     if (fDoFilter) {
400         index |= 4;
401     }
402     // bits 3,4,5 encoding the source bitmap format
403     switch (fBitmap->config()) {
404         case SkBitmap::kARGB_8888_Config:
405             index |= 0;
406             break;
407         case SkBitmap::kRGB_565_Config:
408             index |= 8;
409             break;
410         case SkBitmap::kIndex8_Config:
411             index |= 16;
412             break;
413         case SkBitmap::kARGB_4444_Config:
414             index |= 24;
415             break;
416         case SkBitmap::kA8_Config:
417             index |= 32;
418             fPaintPMColor = SkPreMultiplyColor(paint.getColor());
419             break;
420         default:
421             return false;
422     }
423 
424     static const SampleProc32 gSample32[] = {
425         S32_opaque_D32_nofilter_DXDY,
426         S32_alpha_D32_nofilter_DXDY,
427         S32_opaque_D32_nofilter_DX,
428         S32_alpha_D32_nofilter_DX,
429         S32_opaque_D32_filter_DXDY,
430         S32_alpha_D32_filter_DXDY,
431         S32_opaque_D32_filter_DX,
432         S32_alpha_D32_filter_DX,
433 
434         S16_opaque_D32_nofilter_DXDY,
435         S16_alpha_D32_nofilter_DXDY,
436         S16_opaque_D32_nofilter_DX,
437         S16_alpha_D32_nofilter_DX,
438         S16_opaque_D32_filter_DXDY,
439         S16_alpha_D32_filter_DXDY,
440         S16_opaque_D32_filter_DX,
441         S16_alpha_D32_filter_DX,
442 
443         SI8_opaque_D32_nofilter_DXDY,
444         SI8_alpha_D32_nofilter_DXDY,
445         SI8_opaque_D32_nofilter_DX,
446         SI8_alpha_D32_nofilter_DX,
447         SI8_opaque_D32_filter_DXDY,
448         SI8_alpha_D32_filter_DXDY,
449         SI8_opaque_D32_filter_DX,
450         SI8_alpha_D32_filter_DX,
451 
452         S4444_opaque_D32_nofilter_DXDY,
453         S4444_alpha_D32_nofilter_DXDY,
454         S4444_opaque_D32_nofilter_DX,
455         S4444_alpha_D32_nofilter_DX,
456         S4444_opaque_D32_filter_DXDY,
457         S4444_alpha_D32_filter_DXDY,
458         S4444_opaque_D32_filter_DX,
459         S4444_alpha_D32_filter_DX,
460 
461         // A8 treats alpha/opauqe the same (equally efficient)
462         SA8_alpha_D32_nofilter_DXDY,
463         SA8_alpha_D32_nofilter_DXDY,
464         SA8_alpha_D32_nofilter_DX,
465         SA8_alpha_D32_nofilter_DX,
466         SA8_alpha_D32_filter_DXDY,
467         SA8_alpha_D32_filter_DXDY,
468         SA8_alpha_D32_filter_DX,
469         SA8_alpha_D32_filter_DX
470     };
471 
472     static const SampleProc16 gSample16[] = {
473         S32_D16_nofilter_DXDY,
474         S32_D16_nofilter_DX,
475         S32_D16_filter_DXDY,
476         S32_D16_filter_DX,
477 
478         S16_D16_nofilter_DXDY,
479         S16_D16_nofilter_DX,
480         S16_D16_filter_DXDY,
481         S16_D16_filter_DX,
482 
483         SI8_D16_nofilter_DXDY,
484         SI8_D16_nofilter_DX,
485         SI8_D16_filter_DXDY,
486         SI8_D16_filter_DX,
487 
488         // Don't support 4444 -> 565
489         NULL, NULL, NULL, NULL,
490         // Don't support A8 -> 565
491         NULL, NULL, NULL, NULL
492     };
493 
494     fSampleProc32 = gSample32[index];
495     index >>= 1;    // shift away any opaque/alpha distinction
496     fSampleProc16 = gSample16[index];
497 
498     // our special-case shaderprocs
499     if (S16_D16_filter_DX == fSampleProc16) {
500         if (clamp_clamp) {
501             fShaderProc16 = Clamp_S16_D16_filter_DX_shaderproc;
502         } else if (SkShader::kRepeat_TileMode == fTileModeX &&
503                    SkShader::kRepeat_TileMode == fTileModeY) {
504             fShaderProc16 = Repeat_S16_D16_filter_DX_shaderproc;
505         }
506     }
507 
508     // see if our platform has any accelerated overrides
509     this->platformProcs();
510     return true;
511 }
512 
513 ///////////////////////////////////////////////////////////////////////////////
514 /*
515     The storage requirements for the different matrix procs are as follows,
516     where each X or Y is 2 bytes, and N is the number of pixels/elements:
517 
518     scale/translate     nofilter      Y(4bytes) + N * X
519     affine/perspective  nofilter      N * (X Y)
520     scale/translate     filter        Y Y + N * (X X)
521     affine/perspective  filter        N * (Y Y X X)
522  */
maxCountForBufferSize(size_t bufferSize) const523 int SkBitmapProcState::maxCountForBufferSize(size_t bufferSize) const {
524     int32_t size = static_cast<int32_t>(bufferSize);
525     int perElemShift;
526 
527     size &= ~3; // only care about 4-byte aligned chunks
528     if (fInvType <= (SkMatrix::kTranslate_Mask | SkMatrix::kScale_Mask)) {
529         size -= 4;   // the shared Y (or YY) coordinate
530         if (size < 0) {
531             size = 0;
532         }
533         perElemShift = fDoFilter ? 2 : 1;
534     } else {
535         perElemShift = fDoFilter ? 3 : 2;
536     }
537 
538     return size >> perElemShift;
539 }
540 
541