1 2 /* 3 * Copyright 2017 Google Inc. 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 #ifndef SkShadowUtils_DEFINED 9 #define SkShadowUtils_DEFINED 10 11 #include "SkColor.h" 12 #include "SkPoint3.h" 13 #include "SkScalar.h" 14 #include "../private/SkShadowFlags.h" 15 16 class SkCanvas; 17 class SkPath; 18 class SkResourceCache; 19 20 class SK_API SkShadowUtils { 21 public: 22 /** 23 * Draw an offset spot shadow and outlining ambient shadow for the given path using a disc 24 * light. The shadow may be cached, depending on the path type and canvas matrix. If the 25 * matrix is perspective or the path is volatile, it will not be cached. 26 * 27 * @param canvas The canvas on which to draw the shadows. 28 * @param path The occluder used to generate the shadows. 29 * @param zPlaneParams Values for the plane function which returns the Z offset of the 30 * occluder from the canvas based on local x and y values (the current matrix is not applied). 31 * @param lightPos The 3D position of the light relative to the canvas plane. This is 32 * independent of the canvas's current matrix. 33 * @param lightRadius The radius of the disc light. 34 * @param ambientColor The color of the ambient shadow. 35 * @param spotColor The color of the spot shadow. 36 * @param flags Options controlling opaque occluder optimizations and shadow appearance. See 37 * SkShadowFlags. 38 */ 39 static void DrawShadow(SkCanvas* canvas, const SkPath& path, const SkPoint3& zPlaneParams, 40 const SkPoint3& lightPos, SkScalar lightRadius, 41 SkColor ambientColor, SkColor spotColor, 42 uint32_t flags = SkShadowFlags::kNone_ShadowFlag); 43 44 /** 45 * Deprecated version that uses one color and two alphas, and supports tonal color. 46 * 47 * Draw an offset spot shadow and outlining ambient shadow for the given path using a disc 48 * light. The shadow may be cached, depending on the path type and canvas matrix. If the 49 * matrix is perspective or the path is volatile, it will not be cached. 50 * 51 * @param canvas The canvas on which to draw the shadows. 52 * @param path The occluder used to generate the shadows. 53 * @param zPlaneParams Values for the plane function which returns the Z offset of the 54 * occluder from the canvas based on local x and y values (the current matrix is not applied). 55 * @param lightPos The 3D position of the light relative to the canvas plane. This is 56 * independent of the canvas's current matrix. 57 * @param lightRadius The radius of the disc light. 58 * @param ambientAlpha The maximum alpha of the ambient shadow. 59 * @param spotAlpha The maxium alpha of the spot shadow. 60 * @param color The shadow color. 61 * @param flags Options controlling opaque occluder optimizations and shadow appearance. See 62 * SkShadowFlags. 63 */ 64 static void DrawShadow(SkCanvas* canvas, const SkPath& path, const SkPoint3& zPlane, 65 const SkPoint3& lightPos, SkScalar lightRadius, SkScalar ambientAlpha, 66 SkScalar spotAlpha, SkColor color, 67 uint32_t flags = SkShadowFlags::kNone_ShadowFlag) { 68 SkColor ambientColor; 69 SkColor spotColor; 70 if (flags & SkShadowFlags::kDisableTonalColor_ShadowFlag) { 71 ambientColor = SkColorSetARGB(ambientAlpha*SkColorGetA(color), SkColorGetR(color), 72 SkColorGetG(color), SkColorGetB(color)); 73 spotColor = SkColorSetARGB(spotAlpha*SkColorGetA(color), SkColorGetR(color), 74 SkColorGetG(color), SkColorGetB(color)); 75 } else { 76 SkColor inAmbient = SkColorSetA(color, ambientAlpha*SkColorGetA(color)); 77 SkColor inSpot = SkColorSetA(color, spotAlpha*SkColorGetA(color)); 78 ComputeTonalColors(inAmbient, inSpot, &ambientColor, &spotColor); 79 } 80 81 DrawShadow(canvas, path, zPlane, lightPos, lightRadius, ambientColor, spotColor, flags); 82 } 83 84 /** 85 * Deprecated version with height value (to be removed when Flutter is updated). 86 * 87 * Draw an offset spot shadow and outlining ambient shadow for the given path using a disc 88 * light. 89 * 90 * @param canvas The canvas on which to draw the shadows. 91 * @param path The occluder used to generate the shadows. 92 * @param occluderHeight The vertical offset of the occluder from the canvas. This is 93 * independent of the canvas's current matrix. 94 * @param lightPos The 3D position of the light relative to the canvas plane. This is 95 * independent of the canvas's current matrix. 96 * @param lightRadius The radius of the disc light. 97 * @param ambientAlpha The maximum alpha of the ambient shadow. 98 * @param spotAlpha The maxium alpha of the spot shadow. 99 * @param color The shadow color. 100 * @param flags Options controlling opaque occluder optimizations and shadow appearance. See 101 * SkShadowFlags. 102 */ 103 static void DrawShadow(SkCanvas* canvas, const SkPath& path, SkScalar occluderHeight, 104 const SkPoint3& lightPos, SkScalar lightRadius, SkScalar ambientAlpha, 105 SkScalar spotAlpha, SkColor color, 106 uint32_t flags = SkShadowFlags::kNone_ShadowFlag) { 107 SkPoint3 zPlane = SkPoint3::Make(0, 0, occluderHeight); 108 DrawShadow(canvas, path, zPlane, lightPos, lightRadius, ambientAlpha, spotAlpha, 109 color, flags); 110 } 111 112 /** 113 * Helper routine to compute color values for one-pass tonal alpha. 114 * 115 * @param inAmbientColor Original ambient color 116 * @param inSpotColor Original spot color 117 * @param outAmbientColor Modified ambient color 118 * @param outSpotColor Modified spot color 119 */ 120 static void ComputeTonalColors(SkColor inAmbientColor, SkColor inSpotColor, 121 SkColor* outAmbientColor, SkColor* outSpotColor); 122 }; 123 124 #endif 125