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