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[sdf] Add common elements for 'sdf' and 'bsdf' renderers. 

* src/sdf/ftsdfrend.h (SDF_Rendere_Module, ft_sdf_renderer_class,
ft_bitmap_sdf_renderer_class): New structures.

* src/sdf/ftsdfcommon.h (DEFAULT_SPREAD, MIN_SPREAD_MAX_SPREAD,
USE_SQUARED_DISTANCES): New macros.
(FT_INT_26D6, FT_INT_16D16, FT_26D6_16D16): New macros.
(FT_CALL, VECTOR_LENGTH_16D16): New macros.
(FT_26D6_Vec, FT_16D16_Vec, FT_16D16, FT_26D6, FT_6D10, FT_CBox):
New typedefs.
(square_root): New macro.

* src/sdf/ftsdferrs.h: Add module error setup.
This commit is contained in:
Anuj Verma 2020-08-17 11:40:57 +05:30 committed by Werner Lemberg
parent cd6ff28a17
commit 216270327d
4 changed files with 258 additions and 0 deletions
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17
ChangeLog
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@ -1,3 +1,20 @@
2020-08-17 Anuj Verma <anujv@iitbhilai.ac.in>
[sdf] Add common elements for 'sdf' and 'bsdf' renderers.
* src/sdf/ftsdfrend.h (SDF_Rendere_Module, ft_sdf_renderer_class,
ft_bitmap_sdf_renderer_class): New structures.
* src/sdf/ftsdfcommon.h (DEFAULT_SPREAD, MIN_SPREAD_MAX_SPREAD,
USE_SQUARED_DISTANCES): New macros.
(FT_INT_26D6, FT_INT_16D16, FT_26D6_16D16): New macros.
(FT_CALL, VECTOR_LENGTH_16D16): New macros.
(FT_26D6_Vec, FT_16D16_Vec, FT_16D16, FT_26D6, FT_6D10, FT_CBox):
New typedefs.
(square_root): New macro.
* src/sdf/ftsdferrs.h: Add module error setup.
2020-08-16 Anuj Verma <anujv@iitbhilai.ac.in>
[sdf] Add files for new 'sdf' module.

143
src/sdf/ftsdfcommon.h
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@ -1,7 +1,150 @@
/****************************************************
*
* 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_ */

9
src/sdf/ftsdferrs.h
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@ -2,6 +2,15 @@
#ifndef FTSDFERRS_H_
#define FTSDFERRS_H_
#include <freetype/ftmoderr.h>
#undef FTERRORS_H_
#undef FT_ERR_PREFIX
#define FT_ERR_PREFIX Sdf_Err_
#define FT_ERR_BASE FT_Mod_Err_Sdf
#include <freetype/fterrors.h>
#endif /* FTSDFERRS_H_ */

89
src/sdf/ftsdfrend.h
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@ -2,6 +2,95 @@
#ifndef FTSDFREND_H_
#define FTSDFREND_H_
#include <freetype/ftrender.h>
#include <freetype/ftmodapi.h>
#include <freetype/internal/ftobjs.h>
FT_BEGIN_HEADER
/**************************************************************************
*
* @struct:
* SDF_Renderer_Module
*
* @description:
* This struct extends the native renderer struct `FT_RendererRec`. It
* is basically used to store various parameters required by the
* renderer and some additional parameters that can be used to tweak the
* output of the renderer.
*
* @fields:
* root ::
* The native rendere struct.
*
* spread ::
* This is an essential parameter/property required by the renderer.
* `spread` defines the maximum unsigned value that is present in the
* final SDF output. For the default value check file
* `ftsdfcommon.h`.
*
* flip_sign ::
* By default positive values indicate positions inside of contours,
* i.e., filled by a contour. If this property is true then that
* output will be the opposite of the default, i.e., negative values
* indicate positions inside of contours.
*
* flip_y ::
* Setting this parameter to true makes the output image flipped
* along the y-axis.
*
* overlaps ::
* Set this to true to generate SDF for glyphs having overlapping
* contours. The overlapping support is limited to glyphs that do not
* have self-intersecting contours. Also, removing overlaps require a
* considerable amount of extra memory; additionally, it will not work
* if generating SDF from bitmap.
*
* @note:
* All properties except `overlaps` are valid for both the 'sdf' and
* 'bsdf' renderers.
*/
typedef struct SDF_Renderer_Module_
{
FT_RendererRec root;
FT_UInt spread;
FT_Bool flip_sign;
FT_Bool flip_y;
FT_Bool overlaps;
} SDF_Renderer_Module, *SDF_Renderer;
/**************************************************************************
*
* @renderer:
* ft_sdf_renderer_class
*
* @description:
* Renderer to convert @FT_Outline to signed distance fields.
*
*/
FT_DECLARE_RENDERER( ft_sdf_renderer_class )
/**************************************************************************
*
* @renderer:
* ft_bitmap_sdf_renderer_class
*
* @description:
* This is not exactly a renderer; it is just a converter that
* transforms bitmaps to signed distance fields.
*
* @note:
* This is not a separate module, it is part of the 'sdf' module.
*
*/
FT_DECLARE_RENDERER( ft_bitmap_sdf_renderer_class )
FT_END_HEADER
#endif /* FTSDFREND_H_ */