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, int 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, int 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 */ 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
