SkGradientShader.h revision 8a1c16ff38322f0210116fa7293eb8817c7e477e 
1/*
2 * Copyright (C) 2006 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef SkGradientShader_DEFINED
18#define SkGradientShader_DEFINED
19
20#include "SkShader.h"
21
22class SkUnitMapper;
23
24/** \class SkGradientShader
25
26    SkGradientShader hosts factories for creating subclasses of SkShader that
27    render linear and radial gradients.
28*/
29class SkGradientShader {
30public:
31    /** Returns a shader that generates a linear gradient between the two
32        specified points.
33        <p />
34        CreateLinear returns a shader with a reference count of 1.
35        The caller should decrement the shader's reference count when done with the shader.
36        It is an error for count to be < 2.
37        @param  pts The start and end points for the gradient.
38        @param  colors  The array[count] of colors, to be distributed between the two points
39        @param  pos     May be NULL. array[count] of SkScalars, or NULL, of the relative position of
40                        each corresponding color in the colors array. If this is NULL,
41                        the the colors are distributed evenly between the start and end point.
42                        If this is not null, the values must begin with 0, end with 1.0, and
43                        intermediate values must be strictly increasing.
44        @param  count   Must be >=2. The number of colors (and pos if not NULL) entries.
45        @param  mode    The tiling mode
46        @param  mapper  May be NULL. Callback to modify the spread of the colors.
47    */
48    static SkShader* CreateLinear(  const SkPoint pts[2],
49                                    const SkColor colors[], const SkScalar pos[], int count,
50                                    SkShader::TileMode mode,
51                                    SkUnitMapper* mapper = NULL);
52
53    /** Returns a shader that generates a radial gradient given the center and radius.
54        <p />
55        CreateRadial returns a shader with a reference count of 1.
56        The caller should decrement the shader's reference count when done with the shader.
57        It is an error for colorCount to be < 2, or for radius to be <= 0.
58        @param  center  The center of the circle for this gradient
59        @param  radius  Must be positive. The radius of the circle for this gradient
60        @param  colors  The array[count] of colors, to be distributed between the center and edge of the circle
61        @param  pos     May be NULL. The array[count] of SkScalars, or NULL, of the relative position of
62                        each corresponding color in the colors array. If this is NULL,
63                        the the colors are distributed evenly between the center and edge of the circle.
64                        If this is not null, the values must begin with 0, end with 1.0, and
65                        intermediate values must be strictly increasing.
66        @param  count   Must be >= 2. The number of colors (and pos if not NULL) entries
67        @param  mode    The tiling mode
68        @param  mapper  May be NULL. Callback to modify the spread of the colors.
69    */
70    static SkShader* CreateRadial(  const SkPoint& center, SkScalar radius,
71                                    const SkColor colors[], const SkScalar pos[], int count,
72                                    SkShader::TileMode mode,
73                                    SkUnitMapper* mapper = NULL);
74
75    /** Returns a shader that generates a sweep gradient given a center.
76        <p />
77        CreateRadial returns a shader with a reference count of 1.
78        The caller should decrement the shader's reference count when done with the shader.
79        It is an error for colorCount to be < 2.
80        @param  cx      The X coordinate of the center of the sweep
81        @param  cx      The Y coordinate of the center of the sweep
82        @param  colors  The array[count] of colors, to be distributed around the center.
83        @param  pos     May be NULL. The array[count] of SkScalars, or NULL, of the relative position of
84                        each corresponding color in the colors array. If this is NULL,
85                        the the colors are distributed evenly between the center and edge of the circle.
86                        If this is not null, the values must begin with 0, end with 1.0, and
87                        intermediate values must be strictly increasing.
88        @param  count   Must be >= 2. The number of colors (and pos if not NULL) entries
89        @param  mapper  May be NULL. Callback to modify the spread of the colors.
90    */
91    static SkShader* CreateSweep(SkScalar cx, SkScalar cy,
92                                 const SkColor colors[], const SkScalar pos[],
93                                 int count, SkUnitMapper* mapper = NULL);
94};
95
96#endif
97
98