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