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/*
* Copyright 2014 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkDistanceFieldGen_DEFINED
#define SkDistanceFieldGen_DEFINED
#include "SkTypes.h"
// the max magnitude for the distance field
// distance values are limited to the range (-SK_DistanceFieldMagnitude, SK_DistanceFieldMagnitude]
#define SK_DistanceFieldMagnitude 4
// we need to pad around the original glyph to allow our maximum distance of
// SK_DistanceFieldMagnitude texels away from any edge
#define SK_DistanceFieldPad 4
// the rect we render with is inset from the distance field glyph size to allow for bilerp
#define SK_DistanceFieldInset 2
// For the fragment shader:
// The distance field is constructed as unsigned char values,
// so that the zero value is at 128, and the supported range of distances is [-4 * 127/128, 4].
// Hence our multiplier (width of the range) is 4 * 255/128 and zero threshold is 128/255.
#define SK_DistanceFieldMultiplier "7.96875"
#define SK_DistanceFieldThreshold "0.50196078431"
/** Given 8-bit mask data, generate the associated distance field
* @param distanceField The distance field to be generated. Should already be allocated
* by the client with the padding above.
* @param image 8-bit mask we're using to generate the distance field.
* @param w Width of the original image.
* @param h Height of the original image.
* @param rowBytes Size of each row in the image, in bytes
*/
bool SkGenerateDistanceFieldFromA8Image(unsigned char* distanceField,
const unsigned char* image,
int w, int h, size_t rowBytes);
/** Given 1-bit mask data, generate the associated distance field
* @param distanceField The distance field to be generated. Should already be allocated
* by the client with the padding above.
* @param image 1-bit mask we're using to generate the distance field.
* @param w Width of the original image.
* @param h Height of the original image.
* @param rowBytes Size of each row in the image, in bytes
*/
bool SkGenerateDistanceFieldFromBWImage(unsigned char* distanceField,
const unsigned char* image,
int w, int h, size_t rowBytes);
/** Given width and height of original image, return size (in bytes) of distance field
* @param w Width of the original image.
* @param h Height of the original image.
*/
inline size_t SkComputeDistanceFieldSize(int w, int h) {
return (w + 2*SK_DistanceFieldPad) * (h + 2*SK_DistanceFieldPad) * sizeof(unsigned char);
}
#endif
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