/*
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* Copyright 2014 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkDistanceFieldGen_DEFINED
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#define SkDistanceFieldGen_DEFINED
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#include "SkTypes.h"
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// the max magnitude for the distance field
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// distance values are limited to the range (-SK_DistanceFieldMagnitude, SK_DistanceFieldMagnitude]
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#define SK_DistanceFieldMagnitude 4
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// we need to pad around the original glyph to allow our maximum distance of
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// SK_DistanceFieldMagnitude texels away from any edge
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#define SK_DistanceFieldPad 4
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// the rect we render with is inset from the distance field glyph size to allow for bilerp
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#define SK_DistanceFieldInset 2
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// For the fragment shader:
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// The distance field is constructed as unsigned char values,
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// so that the zero value is at 128, and the supported range of distances is [-4 * 127/128, 4].
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// Hence our multiplier (width of the range) is 4 * 255/128 and zero threshold is 128/255.
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#define SK_DistanceFieldMultiplier "7.96875"
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#define SK_DistanceFieldThreshold "0.50196078431"
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/** Given 8-bit mask data, generate the associated distance field
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* @param distanceField The distance field to be generated. Should already be allocated
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* by the client with the padding above.
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* @param image 8-bit mask we're using to generate the distance field.
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* @param w Width of the original image.
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* @param h Height of the original image.
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* @param rowBytes Size of each row in the image, in bytes
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*/
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bool SkGenerateDistanceFieldFromA8Image(unsigned char* distanceField,
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const unsigned char* image,
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int w, int h, size_t rowBytes);
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/** Given LCD16 mask data (not a 16-bit image), generate the associated distance field
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* @param distanceField The distance field to be generated. Should already be allocated
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* by the client with the padding above.
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* @param image 16-bit LCD data we're using to generate the distance field.
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* @param w Width of the original image.
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* @param h Height of the original image.
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* @param rowBytes Size of each row in the image, in bytes
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*/
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bool SkGenerateDistanceFieldFromLCD16Mask(unsigned char* distanceField,
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const unsigned char* image,
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int w, int h, size_t rowBytes);
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/** Given 1-bit mask data, generate the associated distance field
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* @param distanceField The distance field to be generated. Should already be allocated
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* by the client with the padding above.
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* @param image 1-bit mask we're using to generate the distance field.
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* @param w Width of the original image.
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* @param h Height of the original image.
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* @param rowBytes Size of each row in the image, in bytes
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*/
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bool SkGenerateDistanceFieldFromBWImage(unsigned char* distanceField,
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const unsigned char* image,
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int w, int h, size_t rowBytes);
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/** Given width and height of original image, return size (in bytes) of distance field
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* @param w Width of the original image.
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* @param h Height of the original image.
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*/
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inline size_t SkComputeDistanceFieldSize(int w, int h) {
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return (w + 2*SK_DistanceFieldPad) * (h + 2*SK_DistanceFieldPad) * sizeof(unsigned char);
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}
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#endif
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