ref: 03ceda9701cd8c08ea5b4ee0c2d558a98fc4ed7d
dir: /src/sdf/ftsdfcommon.h/
/****************************************************************************
*
* ftsdfcommon.h
*
* Auxiliary data for Signed Distance Field support (specification only).
*
* Copyright (C) 2020 by
* David Turner, Robert Wilhelm, and Werner Lemberg.
*
* Written by Anuj Verma.
*
* This file is part of the FreeType project, and may only be used,
* modified, and distributed under the terms of the FreeType project
* license, LICENSE.TXT. By continuing to use, modify, or distribute
* this file you indicate that you have read the license and
* understand and accept it fully.
*
*/
/****************************************************
*
* This file contains common functions and properties
* for both the 'sdf' and 'bsdf' renderers.
*
*/
#ifndef FTSDFCOMMON_H_
#define FTSDFCOMMON_H_
#include <ft2build.h>
#include FT_CONFIG_CONFIG_H
#include <freetype/freetype.h>
FT_BEGIN_HEADER
/**************************************************************************
*
* default values (cannot be set individually for each renderer)
*
*/
/* default spread value */
#define DEFAULT_SPREAD 8
/* minimum spread supported by the renderer */
#define MIN_SPREAD 2
/* maximum spread supported by the renderer */
#define MAX_SPREAD 32
/**************************************************************************
*
* common definitions (cannot be set individually for each renderer)
*
*/
/* If this macro is set to 1 the rasterizer uses squared distances for */
/* computation. It can greatly improve the performance but there is a */
/* chance of overflow and artifacts. You can safely use it up to a */
/* pixel size of 128. */
#ifndef USE_SQUARED_DISTANCES
#define USE_SQUARED_DISTANCES 0
#endif
/**************************************************************************
*
* common macros
*
*/
/* convert int to 26.6 fixed-point */
#define FT_INT_26D6( x ) ( x * 64 )
/* convert int to 16.16 fixed-point */
#define FT_INT_16D16( x ) ( x * 65536 )
/* convert 26.6 to 16.16 fixed-point */
#define FT_26D6_16D16( x ) ( x * 1024 )
/* Convenience macro to call a function; it */
/* jumps to label `Exit` if an error occurs. */
#define FT_CALL( x ) do \
{ \
error = ( x ); \
if ( error != FT_Err_Ok ) \
goto Exit; \
} while ( 0 )
/*
* The macro `VECTOR_LENGTH_16D16` computes either squared distances or
* actual distances, depending on the value of `USE_SQUARED_DISTANCES`.
*
* By using squared distances the performance can be greatly improved but
* there is a risk of overflow.
*/
#if USE_SQUARED_DISTANCES
#define VECTOR_LENGTH_16D16( v ) ( FT_MulFix( v.x, v.x ) + \
FT_MulFix( v.y, v.y ) )
#else
#define VECTOR_LENGTH_16D16( v ) FT_Vector_Length( &v )
#endif
/**************************************************************************
*
* common typedefs
*
*/
typedef FT_Vector FT_26D6_Vec; /* with 26.6 fixed-point components */
typedef FT_Vector FT_16D16_Vec; /* with 16.16 fixed-point components */
typedef FT_Fixed FT_16D16; /* 16.16 fixed-point representation */
typedef FT_Fixed FT_26D6; /* 26.6 fixed-point representation */
typedef FT_Short FT_6D10; /* 6.10 fixed-point representation */
typedef FT_BBox FT_CBox; /* control box of a curve */
/**************************************************************************
*
* common functions
*
*/
/*
* Original algorithm:
*
* https://github.com/chmike/fpsqrt
*
* Use this to compute the square root of a 16.16 fixed point number.
*/
static FT_16D16
square_root( FT_16D16 val )
{
FT_ULong t, q, b, r;
r = val;
b = 0x40000000L;
q = 0;
while ( b > 0x40L )
{
t = q + b;
if ( r >= t )
{
r -= t;
q = t + b;
}
r <<= 1;
b >>= 1;
}
q >>= 8;
return q;
}
FT_END_HEADER
#endif /* FTSDFCOMMON_H_ */
/* END */