1/*
2 * Copyright 2017 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#ifndef SkDrawShadowInfo_DEFINED
9#define SkDrawShadowInfo_DEFINED
10
11#include "include/core/SkColor.h"
12#include "include/core/SkPoint.h"
13#include "include/core/SkPoint3.h"
14
15class SkMatrix;
16class SkPath;
17struct SkRect;
18
19struct SkDrawShadowRec {
20 SkPoint3 fZPlaneParams;
21 SkPoint3 fLightPos;
22 SkScalar fLightRadius;
23 SkColor fAmbientColor;
24 SkColor fSpotColor;
25 uint32_t fFlags;
26};
27
28namespace SkDrawShadowMetrics {
29
30static constexpr auto kAmbientHeightFactor = 1.0f / 128.0f;
31static constexpr auto kAmbientGeomFactor = 64.0f;
32// Assuming that we have a light height of 600 for the spot shadow,
33// the spot values will reach their maximum at a height of approximately 292.3077.
34// We'll round up to 300 to keep it simple.
35static constexpr auto kMaxAmbientRadius = 300*kAmbientHeightFactor*kAmbientGeomFactor;
36
37static inline float divide_and_pin(float numer, float denom, float min, float max) {
38 float result = SkTPin(sk_ieee_float_divide(numer, denom), min, max);
39 // ensure that SkTPin handled non-finites correctly
40 SkASSERT(result >= min && result <= max);
41 return result;
42}
43
44inline SkScalar AmbientBlurRadius(SkScalar height) {
45 return std::min(height*kAmbientHeightFactor*kAmbientGeomFactor, kMaxAmbientRadius);
46}
47
48inline SkScalar AmbientRecipAlpha(SkScalar height) {
49 return 1.0f + std::max(height*kAmbientHeightFactor, 0.0f);
50}
51
52inline SkScalar SpotBlurRadius(SkScalar occluderZ, SkScalar lightZ, SkScalar lightRadius) {
53 return lightRadius*divide_and_pin(occluderZ, lightZ - occluderZ, 0.0f, 0.95f);
54}
55
56inline void GetSpotParams(SkScalar occluderZ, SkScalar lightX, SkScalar lightY, SkScalar lightZ,
57 SkScalar lightRadius,
58 SkScalar* blurRadius, SkScalar* scale, SkVector* translate) {
59 SkScalar zRatio = divide_and_pin(occluderZ, lightZ - occluderZ, 0.0f, 0.95f);
60 *blurRadius = lightRadius*zRatio;
61 *scale = divide_and_pin(lightZ, lightZ - occluderZ, 1.0f, 1.95f);
62 *translate = SkVector::Make(-zRatio * lightX, -zRatio * lightY);
63}
64
65// Create the transformation to apply to a path to get its base shadow outline, given the light
66// parameters and the path's 3D transformation (given by ctm and zPlaneParams).
67// Also computes the blur radius to apply the transformed outline.
68bool GetSpotShadowTransform(const SkPoint3& lightPos, SkScalar lightRadius,
69 const SkMatrix& ctm, const SkPoint3& zPlaneParams,
70 const SkRect& pathBounds, SkMatrix* shadowTransform, SkScalar* radius);
71
72// get bounds prior to the ctm being applied
73void GetLocalBounds(const SkPath&, const SkDrawShadowRec&, const SkMatrix& ctm, SkRect* bounds);
74
75} // namespace SkDrawShadowMetrics
76
77#endif
78