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 "SkArithmeticMode.h"
9#include "SkColorPriv.h"
10#include "SkReadBuffer.h"
11#include "SkWriteBuffer.h"
12#include "SkString.h"
13#include "SkUnPreMultiply.h"
14#if SK_SUPPORT_GPU
15#include "SkArithmeticMode_gpu.h"
16#endif
17
18static const bool gUseUnpremul = false;
19
20class SkArithmeticMode_scalar : public SkXfermode {
21public:
22    static SkArithmeticMode_scalar* Create(SkScalar k1, SkScalar k2, SkScalar k3, SkScalar k4,
23                                           bool enforcePMColor) {
24        return SkNEW_ARGS(SkArithmeticMode_scalar, (k1, k2, k3, k4, enforcePMColor));
25    }
26
27    virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count,
28                        const SkAlpha aa[]) const override;
29
30    SK_TO_STRING_OVERRIDE()
31    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkArithmeticMode_scalar)
32
33#if SK_SUPPORT_GPU
34    bool asFragmentProcessor(GrFragmentProcessor**, GrTexture* background) const override;
35
36    bool asXPFactory(GrXPFactory**) const override;
37#endif
38
39private:
40    SkArithmeticMode_scalar(SkScalar k1, SkScalar k2, SkScalar k3, SkScalar k4, bool enforcePMColor) {
41        fK[0] = k1;
42        fK[1] = k2;
43        fK[2] = k3;
44        fK[3] = k4;
45        fEnforcePMColor = enforcePMColor;
46    }
47
48    void flatten(SkWriteBuffer& buffer) const override {
49        buffer.writeScalar(fK[0]);
50        buffer.writeScalar(fK[1]);
51        buffer.writeScalar(fK[2]);
52        buffer.writeScalar(fK[3]);
53        buffer.writeBool(fEnforcePMColor);
54    }
55    SkScalar fK[4];
56    bool fEnforcePMColor;
57
58    friend class SkArithmeticMode;
59
60    typedef SkXfermode INHERITED;
61};
62
63SkFlattenable* SkArithmeticMode_scalar::CreateProc(SkReadBuffer& buffer) {
64    const SkScalar k1 = buffer.readScalar();
65    const SkScalar k2 = buffer.readScalar();
66    const SkScalar k3 = buffer.readScalar();
67    const SkScalar k4 = buffer.readScalar();
68    const bool enforcePMColor = buffer.readBool();
69    return Create(k1, k2, k3, k4, enforcePMColor);
70}
71
72static int pinToByte(int value) {
73    if (value < 0) {
74        value = 0;
75    } else if (value > 255) {
76        value = 255;
77    }
78    return value;
79}
80
81static int arith(SkScalar k1, SkScalar k2, SkScalar k3, SkScalar k4,
82                 int src, int dst) {
83    SkScalar result = SkScalarMul(k1, src * dst) +
84                      SkScalarMul(k2, src) +
85                      SkScalarMul(k3, dst) +
86                      k4;
87    int res = SkScalarRoundToInt(result);
88    return pinToByte(res);
89}
90
91static int blend(int src, int dst, int scale) {
92    return dst + ((src - dst) * scale >> 8);
93}
94
95static bool needsUnpremul(int alpha) {
96    return 0 != alpha && 0xFF != alpha;
97}
98
99void SkArithmeticMode_scalar::xfer32(SkPMColor dst[], const SkPMColor src[],
100                                 int count, const SkAlpha aaCoverage[]) const {
101    SkScalar k1 = fK[0] / 255;
102    SkScalar k2 = fK[1];
103    SkScalar k3 = fK[2];
104    SkScalar k4 = fK[3] * 255;
105
106    for (int i = 0; i < count; ++i) {
107        if ((NULL == aaCoverage) || aaCoverage[i]) {
108            SkPMColor sc = src[i];
109            SkPMColor dc = dst[i];
110
111            int a, r, g, b;
112
113            if (gUseUnpremul) {
114                int sa = SkGetPackedA32(sc);
115                int da = SkGetPackedA32(dc);
116
117                int srcNeedsUnpremul = needsUnpremul(sa);
118                int dstNeedsUnpremul = needsUnpremul(da);
119
120                if (!srcNeedsUnpremul && !dstNeedsUnpremul) {
121                    a = arith(k1, k2, k3, k4, sa, da);
122                    r = arith(k1, k2, k3, k4, SkGetPackedR32(sc), SkGetPackedR32(dc));
123                    g = arith(k1, k2, k3, k4, SkGetPackedG32(sc), SkGetPackedG32(dc));
124                    b = arith(k1, k2, k3, k4, SkGetPackedB32(sc), SkGetPackedB32(dc));
125                } else {
126                    int sr = SkGetPackedR32(sc);
127                    int sg = SkGetPackedG32(sc);
128                    int sb = SkGetPackedB32(sc);
129                    if (srcNeedsUnpremul) {
130                        SkUnPreMultiply::Scale scale = SkUnPreMultiply::GetScale(sa);
131                        sr = SkUnPreMultiply::ApplyScale(scale, sr);
132                        sg = SkUnPreMultiply::ApplyScale(scale, sg);
133                        sb = SkUnPreMultiply::ApplyScale(scale, sb);
134                    }
135
136                    int dr = SkGetPackedR32(dc);
137                    int dg = SkGetPackedG32(dc);
138                    int db = SkGetPackedB32(dc);
139                    if (dstNeedsUnpremul) {
140                        SkUnPreMultiply::Scale scale = SkUnPreMultiply::GetScale(da);
141                        dr = SkUnPreMultiply::ApplyScale(scale, dr);
142                        dg = SkUnPreMultiply::ApplyScale(scale, dg);
143                        db = SkUnPreMultiply::ApplyScale(scale, db);
144                    }
145
146                    a = arith(k1, k2, k3, k4, sa, da);
147                    r = arith(k1, k2, k3, k4, sr, dr);
148                    g = arith(k1, k2, k3, k4, sg, dg);
149                    b = arith(k1, k2, k3, k4, sb, db);
150                }
151            } else {
152                a = arith(k1, k2, k3, k4, SkGetPackedA32(sc), SkGetPackedA32(dc));
153                r = arith(k1, k2, k3, k4, SkGetPackedR32(sc), SkGetPackedR32(dc));
154                g = arith(k1, k2, k3, k4, SkGetPackedG32(sc), SkGetPackedG32(dc));
155                b = arith(k1, k2, k3, k4, SkGetPackedB32(sc), SkGetPackedB32(dc));
156                if (fEnforcePMColor) {
157                    r = SkMin32(r, a);
158                    g = SkMin32(g, a);
159                    b = SkMin32(b, a);
160                }
161            }
162
163            // apply antialias coverage if necessary
164            if (aaCoverage && 0xFF != aaCoverage[i]) {
165                int scale = aaCoverage[i] + (aaCoverage[i] >> 7);
166                a = blend(a, SkGetPackedA32(sc), scale);
167                r = blend(r, SkGetPackedR32(sc), scale);
168                g = blend(g, SkGetPackedG32(sc), scale);
169                b = blend(b, SkGetPackedB32(sc), scale);
170            }
171
172            // turn the result back into premul
173            if (gUseUnpremul && (0xFF != a)) {
174                int scale = a + (a >> 7);
175                r = SkAlphaMul(r, scale);
176                g = SkAlphaMul(g, scale);
177                b = SkAlphaMul(b, scale);
178            }
179            dst[i] = fEnforcePMColor ? SkPackARGB32(a, r, g, b) : SkPackARGB32NoCheck(a, r, g, b);
180        }
181    }
182}
183
184#ifndef SK_IGNORE_TO_STRING
185void SkArithmeticMode_scalar::toString(SkString* str) const {
186    str->append("SkArithmeticMode_scalar: ");
187    for (int i = 0; i < 4; ++i) {
188        str->appendScalar(fK[i]);
189        str->append(" ");
190    }
191    str->appendS32(fEnforcePMColor ? 1 : 0);
192}
193#endif
194
195///////////////////////////////////////////////////////////////////////////////
196
197static bool fitsInBits(SkScalar x, int bits) {
198    return SkScalarAbs(x) < (1 << (bits - 1));
199}
200
201#if 0 // UNUSED
202static int32_t toDot8(SkScalar x) {
203    return (int32_t)(x * 256);
204}
205#endif
206
207SkXfermode* SkArithmeticMode::Create(SkScalar k1, SkScalar k2,
208                                     SkScalar k3, SkScalar k4,
209                                     bool enforcePMColor) {
210    if (fitsInBits(k1, 8) && fitsInBits(k2, 16) &&
211        fitsInBits(k2, 16) && fitsInBits(k2, 24)) {
212
213#if 0 // UNUSED
214        int32_t i1 = toDot8(k1);
215        int32_t i2 = toDot8(k2);
216        int32_t i3 = toDot8(k3);
217        int32_t i4 = toDot8(k4);
218        if (i1) {
219            return SkNEW_ARGS(SkArithmeticMode_quad, (i1, i2, i3, i4));
220        }
221        if (0 == i2) {
222            return SkNEW_ARGS(SkArithmeticMode_dst, (i3, i4));
223        }
224        if (0 == i3) {
225            return SkNEW_ARGS(SkArithmeticMode_src, (i2, i4));
226        }
227        return SkNEW_ARGS(SkArithmeticMode_linear, (i2, i3, i4));
228#endif
229    }
230    return SkArithmeticMode_scalar::Create(k1, k2, k3, k4, enforcePMColor);
231}
232
233
234//////////////////////////////////////////////////////////////////////////////
235
236#if SK_SUPPORT_GPU
237bool SkArithmeticMode_scalar::asFragmentProcessor(GrFragmentProcessor** fp,
238                                                  GrTexture* background) const {
239    if (fp) {
240        *fp = GrArithmeticFP::Create(SkScalarToFloat(fK[0]),
241                                     SkScalarToFloat(fK[1]),
242                                     SkScalarToFloat(fK[2]),
243                                     SkScalarToFloat(fK[3]),
244                                     fEnforcePMColor,
245                                     background);
246    }
247    return true;
248}
249
250bool SkArithmeticMode_scalar::asXPFactory(GrXPFactory** xpf) const {
251    if (xpf) {
252        *xpf = GrArithmeticXPFactory::Create(SkScalarToFloat(fK[0]),
253                                             SkScalarToFloat(fK[1]),
254                                             SkScalarToFloat(fK[2]),
255                                             SkScalarToFloat(fK[3]),
256                                             fEnforcePMColor);
257    }
258    return true;
259}
260
261#endif
262
263SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_START(SkArithmeticMode)
264    SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkArithmeticMode_scalar)
265SK_DEFINE_FLATTENABLE_REGISTRAR_GROUP_END
266