1 /*
2 * Copyright 2022 Google LLC
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 SkAlphaType_DEFINED
9 #define SkAlphaType_DEFINED
10
11 #include "include/private/base/SkAPI.h"
12
13 /** \enum SkAlphaType
14 Describes how to interpret the alpha component of a pixel. A pixel may
15 be opaque, or alpha, describing multiple levels of transparency.
16
17 In simple blending, alpha weights the draw color and the destination
18 color to create a new color. If alpha describes a weight from zero to one:
19
20 new color = draw color * alpha + destination color * (1 - alpha)
21
22 In practice alpha is encoded in two or more bits, where 1.0 equals all bits set.
23
24 RGB may have alpha included in each component value; the stored
25 value is the original RGB multiplied by alpha. Premultiplied color
26 components improve performance.
27 */
28 enum SK_API SkAlphaType : int {
29 kUnknown_SkAlphaType, //!< uninitialized
30 kOpaque_SkAlphaType, //!< pixel is opaque
31 kPremul_SkAlphaType, //!< pixel components are premultiplied by alpha
32 kUnpremul_SkAlphaType, //!< pixel components are independent of alpha
33 kLastEnum_SkAlphaType = kUnpremul_SkAlphaType, //!< last valid value
34 };
35
36 /** Returns true if SkAlphaType equals kOpaque_SkAlphaType.
37
38 kOpaque_SkAlphaType is a hint that the SkColorType is opaque, or that all
39 alpha values are set to their 1.0 equivalent. If SkAlphaType is
40 kOpaque_SkAlphaType, and SkColorType is not opaque, then the result of
41 drawing any pixel with a alpha value less than 1.0 is undefined.
42 */
SkAlphaTypeIsOpaque(SkAlphaType at)43 static inline bool SkAlphaTypeIsOpaque(SkAlphaType at) {
44 return kOpaque_SkAlphaType == at;
45 }
46
47 #endif
48