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 "include/core/SkPaint.h"
9 #include "src/core/SkColorFilterBase.h"
10 #include "src/core/SkColorSpacePriv.h"
11 #include "src/core/SkPaintPriv.h"
12 #include "src/core/SkXfermodePriv.h"
13 #include "src/shaders/SkColorFilterShader.h"
14 #include "src/shaders/SkShaderBase.h"
15
changes_alpha(const SkPaint & paint)16 static bool changes_alpha(const SkPaint& paint) {
17 SkColorFilter* cf = paint.getColorFilter();
18 return cf && !as_CFB(cf)->isAlphaUnchanged();
19 }
20
Overwrites(const SkPaint * paint,ShaderOverrideOpacity overrideOpacity)21 bool SkPaintPriv::Overwrites(const SkPaint* paint, ShaderOverrideOpacity overrideOpacity) {
22 if (!paint) {
23 // No paint means we default to SRC_OVER, so we overwrite iff our shader-override
24 // is opaque, or we don't have one.
25 return overrideOpacity != kNotOpaque_ShaderOverrideOpacity;
26 }
27
28 SkXfermode::SrcColorOpacity opacityType = SkXfermode::kUnknown_SrcColorOpacity;
29
30 if (!changes_alpha(*paint)) {
31 const unsigned paintAlpha = paint->getAlpha();
32 if (0xff == paintAlpha && overrideOpacity != kNotOpaque_ShaderOverrideOpacity &&
33 (!paint->getShader() || paint->getShader()->isOpaque()))
34 {
35 opacityType = SkXfermode::kOpaque_SrcColorOpacity;
36 } else if (0 == paintAlpha) {
37 if (overrideOpacity == kNone_ShaderOverrideOpacity && !paint->getShader()) {
38 opacityType = SkXfermode::kTransparentBlack_SrcColorOpacity;
39 } else {
40 opacityType = SkXfermode::kTransparentAlpha_SrcColorOpacity;
41 }
42 }
43 }
44
45 const auto bm = paint->asBlendMode();
46 if (!bm) {
47 return false; // don't know for sure, so we play it safe and return false.
48 }
49 return SkXfermode::IsOpaque(bm.value(), opacityType);
50 }
51
ShouldDither(const SkPaint & p,SkColorType dstCT)52 bool SkPaintPriv::ShouldDither(const SkPaint& p, SkColorType dstCT) {
53 // The paint dither flag can veto.
54 if (!p.isDither()) {
55 return false;
56 }
57
58 // We always dither 565 or 4444 when requested.
59 if (dstCT == kRGB_565_SkColorType || dstCT == kARGB_4444_SkColorType) {
60 return true;
61 }
62
63 // Otherwise, dither is only needed for non-const paints.
64 return p.getImageFilter() || p.getMaskFilter() ||
65 (p.getShader() && !as_SB(p.getShader())->isConstant());
66 }
67
68 // return true if the paint is just a single color (i.e. not a shader). If its
69 // a shader, then we can't compute a const luminance for it :(
just_a_color(const SkPaint & paint,SkColor * color)70 static bool just_a_color(const SkPaint& paint, SkColor* color) {
71 SkColor c = paint.getColor();
72
73 const auto* shader = as_SB(paint.getShader());
74 if (shader && !shader->asLuminanceColor(&c)) {
75 return false;
76 }
77 if (paint.getColorFilter()) {
78 c = paint.getColorFilter()->filterColor(c);
79 }
80 if (color) {
81 *color = c;
82 }
83 return true;
84 }
85
ComputeLuminanceColor(const SkPaint & paint)86 SkColor SkPaintPriv::ComputeLuminanceColor(const SkPaint& paint) {
87 SkColor c;
88 if (!just_a_color(paint, &c)) {
89 c = SkColorSetRGB(0x7F, 0x80, 0x7F);
90 }
91 return c;
92 }
93
RemoveColorFilter(SkPaint * p,SkColorSpace * dstCS)94 void SkPaintPriv::RemoveColorFilter(SkPaint* p, SkColorSpace* dstCS) {
95 if (SkColorFilter* filter = p->getColorFilter()) {
96 if (SkShader* shader = p->getShader()) {
97 // SkColorFilterShader will modulate the shader color by paint alpha
98 // before applying the filter, so we'll reset it to opaque.
99 p->setShader(sk_make_sp<SkColorFilterShader>(sk_ref_sp(shader),
100 p->getAlphaf(),
101 sk_ref_sp(filter)));
102 p->setAlphaf(1.0f);
103 } else {
104 p->setColor(filter->filterColor4f(p->getColor4f(), sk_srgb_singleton(), dstCS), dstCS);
105 }
106 p->setColorFilter(nullptr);
107 }
108 }
109
ComputeResScaleForStroking(const SkMatrix & matrix)110 SkScalar SkPaintPriv::ComputeResScaleForStroking(const SkMatrix& matrix) {
111 // Not sure how to handle perspective differently, so we just don't try (yet)
112 SkScalar sx = SkPoint::Length(matrix[SkMatrix::kMScaleX], matrix[SkMatrix::kMSkewY]);
113 SkScalar sy = SkPoint::Length(matrix[SkMatrix::kMSkewX], matrix[SkMatrix::kMScaleY]);
114 if (SkScalarsAreFinite(sx, sy)) {
115 SkScalar scale = std::max(sx, sy);
116 if (scale > 0) {
117 return scale;
118 }
119 }
120 return 1;
121 }
122