1 /*
2 * Copyright 2006 The Android Open Source Project
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 #ifndef SkScalerContext_DEFINED
9 #define SkScalerContext_DEFINED
10
11 #include "SkGlyph.h"
12 #include "SkMask.h"
13 #include "SkMaskGamma.h"
14 #include "SkMatrix.h"
15 #include "SkPaint.h"
16 #include "SkTypeface.h"
17
18 class SkDescriptor;
19 class SkMaskFilter;
20 class SkPathEffect;
21 class SkRasterizer;
22
23 struct SkScalerContextEffects {
SkScalerContextEffectsSkScalerContextEffects24 SkScalerContextEffects() : fPathEffect(nullptr), fMaskFilter(nullptr), fRasterizer(nullptr) {}
SkScalerContextEffectsSkScalerContextEffects25 SkScalerContextEffects(SkPathEffect* pe, SkMaskFilter* mf, SkRasterizer* ra)
26 : fPathEffect(pe), fMaskFilter(mf), fRasterizer(ra) {}
27
28 SkPathEffect* fPathEffect;
29 SkMaskFilter* fMaskFilter;
30 SkRasterizer* fRasterizer;
31 };
32
33 enum SkAxisAlignment {
34 kNone_SkAxisAlignment,
35 kX_SkAxisAlignment,
36 kY_SkAxisAlignment
37 };
38
39 /*
40 * To allow this to be forward-declared, it must be its own typename, rather
41 * than a nested struct inside SkScalerContext (where it started).
42 */
43 struct SkScalerContextRec {
44 uint32_t fFontID;
45 SkScalar fTextSize, fPreScaleX, fPreSkewX;
46 SkScalar fPost2x2[2][2];
47 SkScalar fFrameWidth, fMiterLimit;
48
49 //These describe the parameters to create (uniquely identify) the pre-blend.
50 uint32_t fLumBits;
51 uint8_t fDeviceGamma; //2.6, (0.0, 4.0) gamma, 0.0 for sRGB
52 uint8_t fPaintGamma; //2.6, (0.0, 4.0) gamma, 0.0 for sRGB
53 uint8_t fContrast; //0.8+1, [0.0, 1.0] artificial contrast
54 uint8_t fReservedAlign;
55
getDeviceGammaSkScalerContextRec56 SkScalar getDeviceGamma() const {
57 return SkIntToScalar(fDeviceGamma) / (1 << 6);
58 }
setDeviceGammaSkScalerContextRec59 void setDeviceGamma(SkScalar dg) {
60 SkASSERT(0 <= dg && dg < SkIntToScalar(4));
61 fDeviceGamma = SkScalarFloorToInt(dg * (1 << 6));
62 }
63
getPaintGammaSkScalerContextRec64 SkScalar getPaintGamma() const {
65 return SkIntToScalar(fPaintGamma) / (1 << 6);
66 }
setPaintGammaSkScalerContextRec67 void setPaintGamma(SkScalar pg) {
68 SkASSERT(0 <= pg && pg < SkIntToScalar(4));
69 fPaintGamma = SkScalarFloorToInt(pg * (1 << 6));
70 }
71
getContrastSkScalerContextRec72 SkScalar getContrast() const {
73 return SkIntToScalar(fContrast) / ((1 << 8) - 1);
74 }
setContrastSkScalerContextRec75 void setContrast(SkScalar c) {
76 SkASSERT(0 <= c && c <= SK_Scalar1);
77 fContrast = SkScalarRoundToInt(c * ((1 << 8) - 1));
78 }
79
80 /**
81 * Causes the luminance color to be ignored, and the paint and device
82 * gamma to be effectively 1.0
83 */
ignoreGammaSkScalerContextRec84 void ignoreGamma() {
85 setLuminanceColor(SK_ColorTRANSPARENT);
86 setPaintGamma(SK_Scalar1);
87 setDeviceGamma(SK_Scalar1);
88 }
89
90 /**
91 * Causes the luminance color and contrast to be ignored, and the
92 * paint and device gamma to be effectively 1.0.
93 */
ignorePreBlendSkScalerContextRec94 void ignorePreBlend() {
95 ignoreGamma();
96 setContrast(0);
97 }
98
99 uint8_t fMaskFormat;
100 uint8_t fStrokeJoin : 4;
101 uint8_t fStrokeCap : 4;
102 uint16_t fFlags;
103 // Warning: when adding members note that the size of this structure
104 // must be a multiple of 4. SkDescriptor requires that its arguments be
105 // multiples of four and this structure is put in an SkDescriptor in
106 // SkPaint::MakeRec.
107
108 void getMatrixFrom2x2(SkMatrix*) const;
109 void getLocalMatrix(SkMatrix*) const;
110 void getSingleMatrix(SkMatrix*) const;
111
112 /** The kind of scale which will be applied by the underlying port (pre-matrix). */
113 enum PreMatrixScale {
114 kFull_PreMatrixScale, // The underlying port can apply both x and y scale.
115 kVertical_PreMatrixScale, // The underlying port can only apply a y scale.
116 kVerticalInteger_PreMatrixScale // The underlying port can only apply an integer y scale.
117 };
118 /**
119 * Compute useful matrices for use with sizing in underlying libraries.
120 *
121 * There are two kinds of text size, a 'requested/logical size' which is like asking for size
122 * '12' and a 'real' size which is the size after the matrix is applied. The matrices produced
123 * by this method are based on the 'real' size. This method effectively finds the total device
124 * matrix and decomposes it in various ways.
125 *
126 * The most useful decomposition is into 'scale' and 'remaining'. The 'scale' is applied first
127 * and then the 'remaining' to fully apply the total matrix. This decomposition is useful when
128 * the text size ('scale') may have meaning apart from the total matrix. This is true when
129 * hinting, and sometimes true for other properties as well.
130 *
131 * The second (optional) decomposition is of 'remaining' into a non-rotational part
132 * 'remainingWithoutRotation' and a rotational part 'remainingRotation'. The 'scale' is applied
133 * first, then 'remainingWithoutRotation', then 'remainingRotation' to fully apply the total
134 * matrix. This decomposition is helpful when only horizontal metrics can be trusted, so the
135 * 'scale' and 'remainingWithoutRotation' will be handled by the underlying library, but
136 * the final rotation 'remainingRotation' will be handled manually.
137 *
138 * The 'total' matrix is also (optionally) available. This is useful in cases where the
139 * underlying library will not be used, often when working directly with font data.
140 *
141 * The parameters 'scale' and 'remaining' are required, the other pointers may be nullptr.
142 *
143 * @param preMatrixScale the kind of scale to extract from the total matrix.
144 * @param scale the scale extracted from the total matrix (both values positive).
145 * @param remaining apply after scale to apply the total matrix.
146 * @param remainingWithoutRotation apply after scale to apply the total matrix sans rotation.
147 * @param remainingRotation apply after remainingWithoutRotation to apply the total matrix.
148 * @param total the total matrix.
149 * @return false if the matrix was singular. The output will be valid but not invertible.
150 */
151 bool computeMatrices(PreMatrixScale preMatrixScale,
152 SkVector* scale, SkMatrix* remaining,
153 SkMatrix* remainingWithoutRotation = nullptr,
154 SkMatrix* remainingRotation = nullptr,
155 SkMatrix* total = nullptr);
156
157 inline SkPaint::Hinting getHinting() const;
158 inline void setHinting(SkPaint::Hinting);
159
getFormatSkScalerContextRec160 SkMask::Format getFormat() const {
161 return static_cast<SkMask::Format>(fMaskFormat);
162 }
163
getLuminanceColorSkScalerContextRec164 SkColor getLuminanceColor() const {
165 return fLumBits;
166 }
167
setLuminanceColorSkScalerContextRec168 void setLuminanceColor(SkColor c) {
169 fLumBits = c;
170 }
171 };
172
173 //The following typedef hides from the rest of the implementation the number of
174 //most significant bits to consider when creating mask gamma tables. Two bits
175 //per channel was chosen as a balance between fidelity (more bits) and cache
176 //sizes (fewer bits). Three bits per channel was chosen when #303942; (used by
177 //the Chrome UI) turned out too green.
178 typedef SkTMaskGamma<3, 3, 3> SkMaskGamma;
179
180 class SkScalerContext {
181 public:
182 typedef SkScalerContextRec Rec;
183
184 enum Flags {
185 kFrameAndFill_Flag = 0x0001,
186 kDevKernText_Flag = 0x0002,
187 kEmbeddedBitmapText_Flag = 0x0004,
188 kEmbolden_Flag = 0x0008,
189 kSubpixelPositioning_Flag = 0x0010,
190 kForceAutohinting_Flag = 0x0020, // Use auto instead of bytcode hinting if hinting.
191 kVertical_Flag = 0x0040,
192
193 // together, these two flags resulting in a two bit value which matches
194 // up with the SkPaint::Hinting enum.
195 kHinting_Shift = 7, // to shift into the other flags above
196 kHintingBit1_Flag = 0x0080,
197 kHintingBit2_Flag = 0x0100,
198
199 // Pixel geometry information.
200 // only meaningful if fMaskFormat is kLCD16
201 kLCD_Vertical_Flag = 0x0200, // else Horizontal
202 kLCD_BGROrder_Flag = 0x0400, // else RGB order
203
204 // Generate A8 from LCD source (for GDI and CoreGraphics).
205 // only meaningful if fMaskFormat is kA8
206 kGenA8FromLCD_Flag = 0x0800, // could be 0x200 (bit meaning dependent on fMaskFormat)
207 };
208
209 // computed values
210 enum {
211 kHinting_Mask = kHintingBit1_Flag | kHintingBit2_Flag,
212 };
213
214 SkScalerContext(sk_sp<SkTypeface>, const SkScalerContextEffects&, const SkDescriptor*);
215 virtual ~SkScalerContext();
216
getTypeface()217 SkTypeface* getTypeface() const { return fTypeface.get(); }
218
getMaskFormat()219 SkMask::Format getMaskFormat() const {
220 return (SkMask::Format)fRec.fMaskFormat;
221 }
222
isSubpixel()223 bool isSubpixel() const {
224 return SkToBool(fRec.fFlags & kSubpixelPositioning_Flag);
225 }
226
isVertical()227 bool isVertical() const {
228 return SkToBool(fRec.fFlags & kVertical_Flag);
229 }
230
231 /** Return the corresponding glyph for the specified unichar. Since contexts
232 may be chained (under the hood), the glyphID that is returned may in
233 fact correspond to a different font/context. In that case, we use the
234 base-glyph-count to know how to translate back into local glyph space.
235 */
charToGlyphID(SkUnichar uni)236 uint16_t charToGlyphID(SkUnichar uni) {
237 return generateCharToGlyph(uni);
238 }
239
240 /** Map the glyphID to its glyph index, and then to its char code. Unmapped
241 glyphs return zero.
242 */
glyphIDToChar(uint16_t glyphID)243 SkUnichar glyphIDToChar(uint16_t glyphID) {
244 return (glyphID < getGlyphCount()) ? generateGlyphToChar(glyphID) : 0;
245 }
246
getGlyphCount()247 unsigned getGlyphCount() { return this->generateGlyphCount(); }
248 void getAdvance(SkGlyph*);
249 void getMetrics(SkGlyph*);
250 void getImage(const SkGlyph&);
251 void getPath(SkPackedGlyphID, SkPath*);
252 void getFontMetrics(SkPaint::FontMetrics*);
253
254 /** Return the size in bytes of the associated gamma lookup table
255 */
256 static size_t GetGammaLUTSize(SkScalar contrast, SkScalar paintGamma, SkScalar deviceGamma,
257 int* width, int* height);
258
259 /** Get the associated gamma lookup table. The 'data' pointer must point to pre-allocated
260 memory, with size in bytes greater than or equal to the return value of getGammaLUTSize().
261 */
262 static void GetGammaLUTData(SkScalar contrast, SkScalar paintGamma, SkScalar deviceGamma,
263 void* data);
264
265 static void MakeRec(const SkPaint&, const SkSurfaceProps* surfaceProps,
266 const SkMatrix*, Rec* rec);
267 static inline void PostMakeRec(const SkPaint&, Rec*);
268
269 static SkMaskGamma::PreBlend GetMaskPreBlend(const Rec& rec);
270
getRec()271 const Rec& getRec() const { return fRec; }
272
getEffects()273 SkScalerContextEffects getEffects() const {
274 return { fPathEffect.get(), fMaskFilter.get(), fRasterizer.get() };
275 }
276
277 /**
278 * Return the axis (if any) that the baseline for horizontal text should land on.
279 * As an example, the identity matrix will return kX_SkAxisAlignment
280 */
281 SkAxisAlignment computeAxisAlignmentForHText();
282
283 protected:
284 Rec fRec;
285
286 /** Generates the contents of glyph.fAdvanceX and glyph.fAdvanceY.
287 * May call getMetrics if that would be just as fast.
288 */
289 virtual void generateAdvance(SkGlyph* glyph) = 0;
290
291 /** Generates the contents of glyph.fWidth, fHeight, fTop, fLeft,
292 * as well as fAdvanceX and fAdvanceY if not already set.
293 *
294 * TODO: fMaskFormat is set by getMetrics later; cannot be set here.
295 */
296 virtual void generateMetrics(SkGlyph* glyph) = 0;
297
298 /** Generates the contents of glyph.fImage.
299 * When called, glyph.fImage will be pointing to a pre-allocated,
300 * uninitialized region of memory of size glyph.computeImageSize().
301 * This method may change glyph.fMaskFormat if the new image size is
302 * less than or equal to the old image size.
303 *
304 * Because glyph.computeImageSize() will determine the size of fImage,
305 * generateMetrics will be called before generateImage.
306 */
307 virtual void generateImage(const SkGlyph& glyph) = 0;
308
309 /** Sets the passed path to the glyph outline.
310 * If this cannot be done the path is set to empty;
311 * this is indistinguishable from a glyph with an empty path.
312 */
313 virtual void generatePath(SkGlyphID glyphId, SkPath* path) = 0;
314
315 /** Retrieves font metrics. */
316 virtual void generateFontMetrics(SkPaint::FontMetrics*) = 0;
317
318 /** Returns the number of glyphs in the font. */
319 virtual unsigned generateGlyphCount() = 0;
320
321 /** Returns the glyph id for the given unichar.
322 * If there is no 1:1 mapping from the unichar to a glyph id, returns 0.
323 */
324 virtual uint16_t generateCharToGlyph(SkUnichar unichar) = 0;
325
326 /** Returns the unichar for the given glyph id.
327 * If there is no 1:1 mapping from the glyph id to a unichar, returns 0.
328 * The default implementation always returns 0, indicating failure.
329 */
330 virtual SkUnichar generateGlyphToChar(uint16_t glyphId);
331
forceGenerateImageFromPath()332 void forceGenerateImageFromPath() { fGenerateImageFromPath = true; }
forceOffGenerateImageFromPath()333 void forceOffGenerateImageFromPath() { fGenerateImageFromPath = false; }
334
335 private:
336 friend class SkRandomScalerContext; // For debug purposes
337
338 // never null
339 sk_sp<SkTypeface> fTypeface;
340
341 // optional objects, which may be null
342 sk_sp<SkPathEffect> fPathEffect;
343 sk_sp<SkMaskFilter> fMaskFilter;
344 sk_sp<SkRasterizer> fRasterizer;
345
346 // if this is set, we draw the image from a path, rather than
347 // calling generateImage.
348 bool fGenerateImageFromPath;
349
350 void internalGetPath(SkPackedGlyphID id, SkPath* fillPath,
351 SkPath* devPath, SkMatrix* fillToDevMatrix);
352
353 // SkMaskGamma::PreBlend converts linear masks to gamma correcting masks.
354 protected:
355 // Visible to subclasses so that generateImage can apply the pre-blend directly.
356 const SkMaskGamma::PreBlend fPreBlend;
357 private:
358 // When there is a filter, previous steps must create a linear mask
359 // and the pre-blend applied as a final step.
360 const SkMaskGamma::PreBlend fPreBlendForFilter;
361 };
362
363 #define kRec_SkDescriptorTag SkSetFourByteTag('s', 'r', 'e', 'c')
364 #define kPathEffect_SkDescriptorTag SkSetFourByteTag('p', 't', 'h', 'e')
365 #define kMaskFilter_SkDescriptorTag SkSetFourByteTag('m', 's', 'k', 'f')
366 #define kRasterizer_SkDescriptorTag SkSetFourByteTag('r', 'a', 's', 't')
367
368 ///////////////////////////////////////////////////////////////////////////////
369
getHinting()370 SkPaint::Hinting SkScalerContextRec::getHinting() const {
371 unsigned hint = (fFlags & SkScalerContext::kHinting_Mask) >>
372 SkScalerContext::kHinting_Shift;
373 return static_cast<SkPaint::Hinting>(hint);
374 }
375
setHinting(SkPaint::Hinting hinting)376 void SkScalerContextRec::setHinting(SkPaint::Hinting hinting) {
377 fFlags = (fFlags & ~SkScalerContext::kHinting_Mask) |
378 (hinting << SkScalerContext::kHinting_Shift);
379 }
380
381
382 #endif
383