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, so that the zero value is at 128,
23 // and the range is [-4, 4 - 1/255). Hence our multiplier is 8 - 1/32 and zero threshold is 128/255.
24 #define SK_DistanceFieldMultiplier "7.96875"
25 #define SK_DistanceFieldThreshold "0.50196078431"
26
27 /** Given 8-bit mask data, generate the associated distance field
28
29 * @param distanceField The distance field to be generated. Should already be allocated
30 * by the client with the padding above.
31 * @param image 8-bit mask we're using to generate the distance field.
32 * @param w Width of the original image.
33 * @param h Height of the original image.
34 * @param rowBytes Size of each row in the image, in bytes
35 */
36 bool SkGenerateDistanceFieldFromA8Image(unsigned char* distanceField,
37 const unsigned char* image,
38 int w, int h, size_t rowBytes);
39
40 /** Given 1-bit mask data, generate the associated distance field
41
42 * @param distanceField The distance field to be generated. Should already be allocated
43 * by the client with the padding above.
44 * @param image 1-bit mask we're using to generate the distance field.
45 * @param w Width of the original image.
46 * @param h Height of the original image.
47 * @param rowBytes Size of each row in the image, in bytes
48 */
49 bool SkGenerateDistanceFieldFromBWImage(unsigned char* distanceField,
50 const unsigned char* image,
51 int w, int h, size_t rowBytes);
52
53 /** Given width and height of original image, return size (in bytes) of distance field
54 * @param w Width of the original image.
55 * @param h Height of the original image.
56 */
SkComputeDistanceFieldSize(int w,int h)57 inline size_t SkComputeDistanceFieldSize(int w, int h) {
58 return (w + 2*SK_DistanceFieldPad) * (h + 2*SK_DistanceFieldPad) * sizeof(unsigned char);
59 }
60
61 #endif
62