1 /*
2 * Copyright 2014 Google Inc.
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 #ifndef SkDistanceFieldGen_DEFINED
8 #define SkDistanceFieldGen_DEFINED
9
10 #include "SkTypes.h"
11
12 // the max magnitude for the distance field
13 // distance values are limited to the range (-SK_DistanceFieldMagnitude, SK_DistanceFieldMagnitude]
14 #define SK_DistanceFieldMagnitude 4
15 // we need to pad around the original glyph to allow our maximum distance of
16 // SK_DistanceFieldMagnitude texels away from any edge
17 #define SK_DistanceFieldPad 4
18 // the rect we render with is inset from the distance field glyph size to allow for bilerp
19 #define SK_DistanceFieldInset 2
20
21 // For the fragment shader:
22 // The distance field is constructed as unsigned char values,
23 // so that the zero value is at 128, and the supported range of distances is [-4 * 127/128, 4].
24 // Hence our multiplier (width of the range) is 4 * 255/128 and zero threshold is 128/255.
25 #define SK_DistanceFieldMultiplier "7.96875"
26 #define SK_DistanceFieldThreshold "0.50196078431"
27
28 /** Given 8-bit mask data, generate the associated distance field
29
30 * @param distanceField The distance field to be generated. Should already be allocated
31 * by the client with the padding above.
32 * @param image 8-bit mask we're using to generate the distance field.
33 * @param w Width of the original image.
34 * @param h Height of the original image.
35 * @param rowBytes Size of each row in the image, in bytes
36 */
37 bool SkGenerateDistanceFieldFromA8Image(unsigned char* distanceField,
38 const unsigned char* image,
39 int w, int h, size_t rowBytes);
40
41 /** Given LCD16 mask data (not a 16-bit image), generate the associated distance field
42
43 * @param distanceField The distance field to be generated. Should already be allocated
44 * by the client with the padding above.
45 * @param image 16-bit LCD data we're using to generate the distance field.
46 * @param w Width of the original image.
47 * @param h Height of the original image.
48 * @param rowBytes Size of each row in the image, in bytes
49 */
50 bool SkGenerateDistanceFieldFromLCD16Mask(unsigned char* distanceField,
51 const unsigned char* image,
52 int w, int h, size_t rowBytes);
53
54 /** Given 1-bit mask data, generate the associated distance field
55
56 * @param distanceField The distance field to be generated. Should already be allocated
57 * by the client with the padding above.
58 * @param image 1-bit mask we're using to generate the distance field.
59 * @param w Width of the original image.
60 * @param h Height of the original image.
61 * @param rowBytes Size of each row in the image, in bytes
62 */
63 bool SkGenerateDistanceFieldFromBWImage(unsigned char* distanceField,
64 const unsigned char* image,
65 int w, int h, size_t rowBytes);
66
67 /** Given width and height of original image, return size (in bytes) of distance field
68 * @param w Width of the original image.
69 * @param h Height of the original image.
70 */
SkComputeDistanceFieldSize(int w,int h)71 inline size_t SkComputeDistanceFieldSize(int w, int h) {
72 return (w + 2*SK_DistanceFieldPad) * (h + 2*SK_DistanceFieldPad) * sizeof(unsigned char);
73 }
74
75 #endif
76