103 lines
4.7 KiB
C++
103 lines
4.7 KiB
C++
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/*
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* Copyright 2017 Google LLC
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkShadowUtils_DEFINED
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#define SkShadowUtils_DEFINED
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#include "include/core/SkColor.h"
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#include "include/core/SkScalar.h"
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#include "include/core/SkTypes.h"
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#include <cstdint>
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class SkCanvas;
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class SkMatrix;
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class SkPath;
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struct SkPoint3;
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struct SkRect;
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enum SkShadowFlags {
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kNone_ShadowFlag = 0x00,
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/** The occluding object is not opaque. Knowing that the occluder is opaque allows
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* us to cull shadow geometry behind it and improve performance. */
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kTransparentOccluder_ShadowFlag = 0x01,
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/** Don't try to use analytic shadows. */
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kGeometricOnly_ShadowFlag = 0x02,
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/** Light position represents a direction, light radius is blur radius at elevation 1 */
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kDirectionalLight_ShadowFlag = 0x04,
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/** Concave paths will only use blur to generate the shadow */
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kConcaveBlurOnly_ShadowFlag = 0x08,
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/** mask for all shadow flags */
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kAll_ShadowFlag = 0x0F
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};
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class SK_API SkShadowUtils {
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public:
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/**
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* Draw an offset spot shadow and outlining ambient shadow for the given path using a disc
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* light. The shadow may be cached, depending on the path type and canvas matrix. If the
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* matrix is perspective or the path is volatile, it will not be cached.
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*
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* @param canvas The canvas on which to draw the shadows.
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* @param path The occluder used to generate the shadows.
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* @param zPlaneParams Values for the plane function which returns the Z offset of the
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* occluder from the canvas based on local x and y values (the current matrix is not applied).
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* @param lightPos Generally, the 3D position of the light relative to the canvas plane.
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* If kDirectionalLight_ShadowFlag is set, this specifies a vector pointing
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* towards the light.
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* @param lightRadius Generally, the radius of the disc light.
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* If DirectionalLight_ShadowFlag is set, this specifies the amount of
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* blur when the occluder is at Z offset == 1. The blur will grow linearly
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* as the Z value increases.
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* @param ambientColor The color of the ambient shadow.
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* @param spotColor The color of the spot shadow.
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* @param flags Options controlling opaque occluder optimizations, shadow appearance,
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* and light position. See SkShadowFlags.
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*/
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static void DrawShadow(SkCanvas* canvas, const SkPath& path, const SkPoint3& zPlaneParams,
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const SkPoint3& lightPos, SkScalar lightRadius,
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SkColor ambientColor, SkColor spotColor,
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uint32_t flags = SkShadowFlags::kNone_ShadowFlag);
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/**
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* Generate bounding box for shadows relative to path. Includes both the ambient and spot
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* shadow bounds.
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*
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* @param ctm Current transformation matrix to device space.
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* @param path The occluder used to generate the shadows.
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* @param zPlaneParams Values for the plane function which returns the Z offset of the
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* occluder from the canvas based on local x and y values (the current matrix is not applied).
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* @param lightPos Generally, the 3D position of the light relative to the canvas plane.
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* If kDirectionalLight_ShadowFlag is set, this specifies a vector pointing
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* towards the light.
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* @param lightRadius Generally, the radius of the disc light.
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* If DirectionalLight_ShadowFlag is set, this specifies the amount of
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* blur when the occluder is at Z offset == 1. The blur will grow linearly
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* as the Z value increases.
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* @param flags Options controlling opaque occluder optimizations, shadow appearance,
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* and light position. See SkShadowFlags.
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* @param bounds Return value for shadow bounding box.
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* @return Returns true if successful, false otherwise.
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*/
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static bool GetLocalBounds(const SkMatrix& ctm, const SkPath& path,
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const SkPoint3& zPlaneParams, const SkPoint3& lightPos,
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SkScalar lightRadius, uint32_t flags, SkRect* bounds);
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/**
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* Helper routine to compute color values for one-pass tonal alpha.
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*
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* @param inAmbientColor Original ambient color
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* @param inSpotColor Original spot color
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* @param outAmbientColor Modified ambient color
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* @param outSpotColor Modified spot color
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*/
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static void ComputeTonalColors(SkColor inAmbientColor, SkColor inSpotColor,
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SkColor* outAmbientColor, SkColor* outSpotColor);
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};
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#endif
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