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freetype2/src/sdf/ftsdf.c

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#include <freetype/internal/ftobjs.h>
#include <freetype/internal/ftdebug.h>
#include <freetype/fttrigon.h>
#include "ftsdf.h"
#include "ftsdferrs.h"
/**************************************************************************
*
* for tracking memory used
*
*/
#ifdef FT_DEBUG_LEVEL_TRACE
#undef FT_DEBUG_INNER
#undef FT_ASSIGNP_INNER
#define FT_DEBUG_INNER( exp ) ( _ft_debug_file = __FILE__, \
_ft_debug_lineno = line, \
(exp) )
#define FT_ASSIGNP_INNER( p, exp ) ( _ft_debug_file = __FILE__, \
_ft_debug_lineno = line, \
FT_ASSIGNP( p, exp ) )
/* To be used with `FT_Memory::user' in order to track */
/* memory allocations. */
typedef struct SDF_MemoryUser_
{
void* prev_user;
FT_Long total_usage;
} SDF_MemoryUser;
/* Use these functions while allocating and deallocating */
/* memory. These macros restore the previous user pointer */
/* before calling the allocation functions, which is ess- */
/* ential if the program is compiled with macro */
/* `FT_DEBUG_MEMORY'. */
static FT_Pointer
sdf_alloc( FT_Memory memory,
FT_Long size,
FT_Error* err,
FT_Int line )
{
SDF_MemoryUser* current_user;
FT_Pointer ptr;
FT_Error error;
current_user = (SDF_MemoryUser*)memory->user;
memory->user = current_user->prev_user;
if ( !FT_QALLOC( ptr, size ) )
current_user->total_usage += size;
memory->user = (void*)current_user;
*err = error;
return ptr;
}
static void
sdf_free( FT_Memory memory,
FT_Pointer ptr,
FT_Int line )
{
SDF_MemoryUser* current_user;
current_user = (SDF_MemoryUser*)memory->user;
memory->user = current_user->prev_user;
FT_FREE( ptr );
memory->user = (void*)current_user;
}
#define SDF_ALLOC( ptr, size ) \
( ptr = sdf_alloc( memory, size, \
&error, __LINE__ ), \
error != 0 )
#define SDF_FREE( ptr ) \
sdf_free( memory, ptr, __LINE__ ) \
#define SDF_MEMORY_TRACKER_DECLARE() SDF_MemoryUser sdf_memory_user
#define SDF_MEMORY_TRACKER_SETUP() \
sdf_memory_user.prev_user = memory->user; \
sdf_memory_user.total_usage = 0; \
memory->user = &sdf_memory_user
#define SDF_MEMORY_TRACKER_DONE() \
memory->user = sdf_memory_user.prev_user; \
FT_TRACE0(( "[sdf] sdf_raster_render: " \
"Total memory used = %ld\n", \
sdf_memory_user.total_usage ))
#else
/* Use the native allocation functions. */
#define SDF_ALLOC FT_QALLOC
#define SDF_FREE FT_FREE
/* Do nothing */
#define SDF_MEMORY_TRACKER_DECLARE() FT_DUMMY_STMNT
#define SDF_MEMORY_TRACKER_SETUP() FT_DUMMY_STMNT
#define SDF_MEMORY_TRACKER_DONE() FT_DUMMY_STMNT
#endif
/**************************************************************************
*
* definitions
*
*/
/* If it is defined to 1 then the rasterizer will use Newton-Raphson's */
/* method for finding shortest distance from a point to a conic curve. */
/* The other method is an analytical method which find the roots of a */
/* cubic polynomial to find the shortest distance. But the analytical */
/* method has underflow as of now. So, use the Newton's method if there */
/* is any visible artifacts. */
#ifndef USE_NEWTON_FOR_CONIC
# define USE_NEWTON_FOR_CONIC 1
#endif
/* `MAX_NEWTON_DIVISIONS' is the number of intervals the bezier curve */
/* is sampled and checked for shortest distance. */
#define MAX_NEWTON_DIVISIONS 4
/* `MAX_NEWTON_STEPS' is the number of steps of Newton's iterations in */
/* each interval of the bezier curve. Basically for each division we */
/* run the Newton's approximation (i.e. x -= Q( t ) / Q'( t )) to get */
/* the shortest distance. */
#define MAX_NEWTON_STEPS 4
/* This is the distance in 16.16 which is used for corner resolving. If */
/* the difference of two distance is less than `CORNER_CHECK_EPSILON' */
/* then they will be checked for corner if they have ambiguity. */
#define CORNER_CHECK_EPSILON 32
#if 0
/* Coarse grid dimension. Probably will be removed in the future cause */
/* coarse grid optimization is the slowest. */
#define CG_DIMEN 8
#endif
/**************************************************************************
*
* macros
*
*/
#define MUL_26D6( a, b ) ( ( ( a ) * ( b ) ) / 64 )
#define VEC_26D6_DOT( p, q ) ( MUL_26D6( p.x, q.x ) + \
MUL_26D6( p.y, q.y ) )
/**************************************************************************
*
* structures and enums
*
*/
/**************************************************************************
*
* @Struct:
* SDF_TRaster
*
* @Description:
* This struct is used in place of `FT_Raster' and is stored within
* the internal freetype renderer struct. While rasterizing this is
* passed to the `FT_Raster_Render_Func' function, which then can be
* used however we want.
*
* @Fields:
* memory ::
* Used internally to allocate intermediate memory while raterizing.
*
*/
typedef struct SDF_TRaster_
{
FT_Memory memory;
} SDF_TRaster;
/**************************************************************************
*
* @Enum:
* SDF_Edge_Type
*
* @Description:
* Enumeration of all the types of curve present in fonts.
*
* @Fields:
* SDF_EDGE_UNDEFINED ::
* Undefined edge, simply used to initialize and detect errors.
*
* SDF_EDGE_LINE ::
* Line segment with start and end point.
*
* SDF_EDGE_CONIC ::
* A conic/quadratic bezier curve with start, end and on control
* point.
*
* SDF_EDGE_CUBIC ::
* A cubic bezier curve with start, end and two control points.
*
*/
typedef enum SDF_Edge_Type_
{
SDF_EDGE_UNDEFINED = 0,
SDF_EDGE_LINE = 1,
SDF_EDGE_CONIC = 2,
SDF_EDGE_CUBIC = 3
} SDF_Edge_Type;
/**************************************************************************
*
* @Enum:
* SDF_Contour_Orientation
*
* @Description:
* Enumeration of all the orientation of a contour. We determine the
* orientation by calculating the area covered by a contour.
*
* @Fields:
* SDF_ORIENTATION_NONE ::
* Undefined orientation, simply used to initialize and detect errors.
*
* SDF_ORIENTATION_CW ::
* Clockwise orientation. (positive area covered)
*
* SDF_ORIENTATION_ACW ::
* Anti-clockwise orientation. (negative area covered)
*
* @Note:
* The orientation is independent of the fill rule of a `FT_Outline',
* that means the fill will be different for different font formats.
* For example, for TrueType fonts clockwise contours are filled, while
* for OpenType fonts anti-clockwise contours are filled. To determine
* the propert fill rule use `FT_Outline_Get_Orientation'.
*
*/
typedef enum SDF_Contour_Orientation_
{
SDF_ORIENTATION_NONE = 0,
SDF_ORIENTATION_CW = 1,
SDF_ORIENTATION_ACW = 2
} SDF_Contour_Orientation;
/**************************************************************************
*
* @Enum:
* SDF_Edge
*
* @Description:
* Represent an edge of a contour.
*
* @Fields:
* start_pos ::
* Start position of an edge. Valid for all types of edges.
*
* end_pos ::
* Etart position of an edge. Valid for all types of edges.
*
* control_a ::
* A control point of the edge. Valid only for `SDF_EDGE_CONIC'
* and `SDF_EDGE_CUBIC'.
*
* control_b ::
* Another control point of the edge. Valid only for `SDF_EDGE_CONIC'.
*
* edge_type ::
* Type of the edge, see `SDF_Edge_Type' for all possible edge types.
*
* next ::
* Used to create a singly linked list, which can be interpreted
* as a contour.
*
*/
typedef struct SDF_Edge_
{
FT_26D6_Vec start_pos;
FT_26D6_Vec end_pos;
FT_26D6_Vec control_a;
FT_26D6_Vec control_b;
SDF_Edge_Type edge_type;
struct SDF_Edge_* next;
} SDF_Edge;
/**************************************************************************
*
* @Enum:
* SDF_Contour
*
* @Description:
* Represent a complete contour, which contains a list of edges.
*
* @Fields:
* last_pos ::
* Contains the position of the `end_pos' of the last edge
* in the list of edges. Useful while decomposing the outline
* using `FT_Outline_Decompose'.
*
* edges ::
* Linked list of all the edges that make the contour.
*
* next ::
* Used to create a singly linked list, which can be interpreted
* as a complete shape or `FT_Outline'.
*
*/
typedef struct SDF_Contour_
{
FT_26D6_Vec last_pos;
SDF_Edge* edges;
struct SDF_Contour_* next;
} SDF_Contour;
/**************************************************************************
*
* @Enum:
* SDF_Shape
*
* @Description:
* Represent a complete shape which is the decomposition of `FT_Outline'.
*
* @Fields:
* memory ::
* Used internally to allocate memory.
*
* contours ::
* Linked list of all the contours that make the shape.
*
*/
typedef struct SDF_Shape_
{
FT_Memory memory;
SDF_Contour* contours;
} SDF_Shape;
/**************************************************************************
*
* @Enum:
* SDF_Signed_Distance
*
* @Description:
* Represent signed distance of a point, i.e. the distance of the
* edge nearest to the point.
*
* @Fields:
* distance ::
* Distance of the point from the nearest edge. Can be squared or
* absolute depending on the `USE_SQUARED_DISTANCES' parameter
* defined in `ftsdfcommon.h'.
*
* cross ::
* Cross product of the shortest distance vector (i.e. the vector
* the point to the nearest edge) and the direction of the edge
* at the nearest point. This is used to resolve any ambiguity
* in the sign.
*
* sign ::
* Represent weather the distance vector is outside or inside the
* contour corresponding to the edge.
*
* @Note:
* The `sign' may or may not be correct, therefore it must be checked
* properly in case there is an ambiguity.
*
*/
typedef struct SDF_Signed_Distance_
{
FT_16D16 distance;
FT_16D16 cross;
FT_Char sign;
} SDF_Signed_Distance;
/**************************************************************************
*
* @Enum:
* SDF_Params
*
* @Description:
* Yet another internal parameters required by the rasterizer.
*
* @Fields:
* orientation ::
* This is not the `SDF_Contour_Orientation', this is the
* `FT_Orientation', which determine weather clockwise is to
* be filled or anti-clockwise.
*
* flip_sign ::
* Simply flip the sign if this is true. By default the points
* filled by the outline are positive.
*
* flip_y ::
* If set to true the output bitmap will be upside down. Can be
* useful because OpenGL and DirectX have different coordinate
* system for textures.
*
* overload_sign ::
* In the subdivision and bounding box optimization, the default
* outside sign is taken as -1. This parameter can be used to
* modify that behaviour. For example, while generating SDF for
* single counter-clockwise contour the outside sign should be 1.
*
*/
typedef struct SDF_Params_
{
FT_Orientation orientation;
FT_Bool flip_sign;
FT_Bool flip_y;
FT_Int overload_sign;
} SDF_Params;
/**************************************************************************
*
* constants, initializer and destructor
*
*/
static
const FT_Vector zero_vector = { 0, 0 };
static
const SDF_Edge null_edge = { { 0, 0 }, { 0, 0 },
{ 0, 0 }, { 0, 0 },
SDF_EDGE_UNDEFINED, NULL };
static
const SDF_Contour null_contour = { { 0, 0 }, NULL, NULL };
static
const SDF_Shape null_shape = { NULL, NULL };
static
const SDF_Signed_Distance max_sdf = { INT_MAX, 0, 0 };
/* Creates a new `SDF_Edge' on the heap and assigns the `edge' */
/* pointer to the newly allocated memory. */
static FT_Error
sdf_edge_new( FT_Memory memory,
SDF_Edge** edge )
{
FT_Error error = FT_Err_Ok;
SDF_Edge* ptr = NULL;
if ( !memory || !edge )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
if ( !SDF_ALLOC( ptr, sizeof( *ptr ) ) )
{
*ptr = null_edge;
*edge = ptr;
}
Exit:
return error;
}
/* Frees the allocated `edge' variable. */
static void
sdf_edge_done( FT_Memory memory,
SDF_Edge** edge )
{
if ( !memory || !edge || !*edge )
return;
SDF_FREE( *edge );
}
/* Creates a new `SDF_Contour' on the heap and assigns */
/* the `contour' pointer to the newly allocated memory. */
static FT_Error
sdf_contour_new( FT_Memory memory,
SDF_Contour** contour )
{
FT_Error error = FT_Err_Ok;
SDF_Contour* ptr = NULL;
if ( !memory || !contour )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
if ( !SDF_ALLOC( ptr, sizeof( *ptr ) ) )
{
*ptr = null_contour;
*contour = ptr;
}
Exit:
return error;
}
/* Frees the allocated `contour' variable and also frees */
/* the list of edges. */
static void
sdf_contour_done( FT_Memory memory,
SDF_Contour** contour )
{
SDF_Edge* edges;
SDF_Edge* temp;
if ( !memory || !contour || !*contour )
return;
edges = (*contour)->edges;
/* release all the edges */
while ( edges )
{
temp = edges;
edges = edges->next;
sdf_edge_done( memory, &temp );
}
SDF_FREE( *contour );
}
/* Creates a new `SDF_Shape' on the heap and assigns */
/* the `shape' pointer to the newly allocated memory. */
static FT_Error
sdf_shape_new( FT_Memory memory,
SDF_Shape** shape )
{
FT_Error error = FT_Err_Ok;
SDF_Shape* ptr = NULL;
if ( !memory || !shape )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
if ( !SDF_ALLOC( ptr, sizeof( *ptr ) ) )
{
*ptr = null_shape;
ptr->memory = memory;
*shape = ptr;
}
Exit:
return error;
}
/* Frees the allocated `shape' variable and also frees */
/* the list of contours. */
static void
sdf_shape_done( SDF_Shape** shape )
{
FT_Memory memory;
SDF_Contour* contours;
SDF_Contour* temp;
if ( !shape || !*shape )
return;
memory = (*shape)->memory;
contours = (*shape)->contours;
if ( !memory )
return;
/* release all the contours */
while ( contours )
{
temp = contours;
contours = contours->next;
sdf_contour_done( memory, &temp );
}
/* release the allocated shape struct */
SDF_FREE( *shape );
}
/**************************************************************************
*
* shape decomposition functions
*
*/
/* This function is called when walking along a new contour */
/* so add a new contour to the shape's list. */
static FT_Error
sdf_move_to( const FT_26D6_Vec* to,
void* user )
{
SDF_Shape* shape = ( SDF_Shape* )user;
SDF_Contour* contour = NULL;
FT_Error error = FT_Err_Ok;
FT_Memory memory = shape->memory;
if ( !to || !user )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
FT_CALL( sdf_contour_new( memory, &contour ) );
contour->last_pos = *to;
contour->next = shape->contours;
shape->contours = contour;
Exit:
return error;
}
/* This function is called when there is a line in the */
/* contour. The line is from the previous edge point to */
/* the parameter `to'. */
static FT_Error
sdf_line_to( const FT_26D6_Vec* to,
void* user )
{
SDF_Shape* shape = ( SDF_Shape* )user;
SDF_Edge* edge = NULL;
SDF_Contour* contour = NULL;
FT_Error error = FT_Err_Ok;
FT_Memory memory = shape->memory;
if ( !to || !user )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
contour = shape->contours;
if ( contour->last_pos.x == to->x &&
contour->last_pos.y == to->y )
goto Exit;
FT_CALL( sdf_edge_new( memory, &edge ) );
edge->edge_type = SDF_EDGE_LINE;
edge->start_pos = contour->last_pos;
edge->end_pos = *to;
edge->next = contour->edges;
contour->edges = edge;
contour->last_pos = *to;
Exit:
return error;
}
/* This function is called when there is a conic bezier */
/* curve in the contour. The bezier is from the previous */
/* edge point to the parameter `to' with the control */
/* point being `control_1'. */
static FT_Error
sdf_conic_to( const FT_26D6_Vec* control_1,
const FT_26D6_Vec* to,
void* user )
{
SDF_Shape* shape = ( SDF_Shape* )user;
SDF_Edge* edge = NULL;
SDF_Contour* contour = NULL;
FT_Error error = FT_Err_Ok;
FT_Memory memory = shape->memory;
if ( !control_1 || !to || !user )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
contour = shape->contours;
FT_CALL( sdf_edge_new( memory, &edge ) );
edge->edge_type = SDF_EDGE_CONIC;
edge->start_pos = contour->last_pos;
edge->control_a = *control_1;
edge->end_pos = *to;
edge->next = contour->edges;
contour->edges = edge;
contour->last_pos = *to;
Exit:
return error;
}
/* This function is called when there is a cubic bezier */
/* curve in the contour. The bezier is from the previous */
/* edge point to the parameter `to' with one control */
/* point being `control_1' and another `control_2'. */
static FT_Error
sdf_cubic_to( const FT_26D6_Vec* control_1,
const FT_26D6_Vec* control_2,
const FT_26D6_Vec* to,
void* user )
{
SDF_Shape* shape = ( SDF_Shape* )user;
SDF_Edge* edge = NULL;
SDF_Contour* contour = NULL;
FT_Error error = FT_Err_Ok;
FT_Memory memory = shape->memory;
if ( !control_2 || !control_1 || !to || !user )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
contour = shape->contours;
FT_CALL( sdf_edge_new( memory, &edge ) );
edge->edge_type = SDF_EDGE_CUBIC;
edge->start_pos = contour->last_pos;
edge->control_a = *control_1;
edge->control_b = *control_2;
edge->end_pos = *to;
edge->next = contour->edges;
contour->edges = edge;
contour->last_pos = *to;
Exit:
return error;
}
/* Construct the struct to hold all four outline */
/* decomposition functions. */
FT_DEFINE_OUTLINE_FUNCS(
sdf_decompose_funcs,
(FT_Outline_MoveTo_Func) sdf_move_to, /* move_to */
(FT_Outline_LineTo_Func) sdf_line_to, /* line_to */
(FT_Outline_ConicTo_Func) sdf_conic_to, /* conic_to */
(FT_Outline_CubicTo_Func) sdf_cubic_to, /* cubic_to */
0, /* shift */
0 /* delta */
)
/* The function decomposes the outline and puts it */
/* into the `shape' struct. */
static FT_Error
sdf_outline_decompose( FT_Outline* outline,
SDF_Shape* shape )
{
FT_Error error = FT_Err_Ok;
if ( !outline || !shape )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
error = FT_Outline_Decompose( outline,
&sdf_decompose_funcs,
(void*)shape );
Exit:
return error;
}
/**************************************************************************
*
* utility functions
*
*/
/* The function returns the control box of a edge. */
/* The control box is a rectangle in which all the */
/* control points can fit tightly. */
static FT_CBox
get_control_box( SDF_Edge edge )
{
FT_CBox cbox;
FT_Bool is_set = 0;
switch (edge.edge_type) {
case SDF_EDGE_CUBIC:
{
cbox.xMin = edge.control_b.x;
cbox.xMax = edge.control_b.x;
cbox.yMin = edge.control_b.y;
cbox.yMax = edge.control_b.y;
is_set = 1;
}
case SDF_EDGE_CONIC:
{
if ( is_set )
{
cbox.xMin = edge.control_a.x < cbox.xMin ?
edge.control_a.x : cbox.xMin;
cbox.xMax = edge.control_a.x > cbox.xMax ?
edge.control_a.x : cbox.xMax;
cbox.yMin = edge.control_a.y < cbox.yMin ?
edge.control_a.y : cbox.yMin;
cbox.yMax = edge.control_a.y > cbox.yMax ?
edge.control_a.y : cbox.yMax;
}
else
{
cbox.xMin = edge.control_a.x;
cbox.xMax = edge.control_a.x;
cbox.yMin = edge.control_a.y;
cbox.yMax = edge.control_a.y;
is_set = 1;
}
}
case SDF_EDGE_LINE:
{
if ( is_set )
{
cbox.xMin = edge.start_pos.x < cbox.xMin ?
edge.start_pos.x : cbox.xMin;
cbox.xMax = edge.start_pos.x > cbox.xMax ?
edge.start_pos.x : cbox.xMax;
cbox.yMin = edge.start_pos.y < cbox.yMin ?
edge.start_pos.y : cbox.yMin;
cbox.yMax = edge.start_pos.y > cbox.yMax ?
edge.start_pos.y : cbox.yMax;
}
else
{
cbox.xMin = edge.start_pos.x;
cbox.xMax = edge.start_pos.x;
cbox.yMin = edge.start_pos.y;
cbox.yMax = edge.start_pos.y;
}
cbox.xMin = edge.end_pos.x < cbox.xMin ?
edge.end_pos.x : cbox.xMin;
cbox.xMax = edge.end_pos.x > cbox.xMax ?
edge.end_pos.x : cbox.xMax;
cbox.yMin = edge.end_pos.y < cbox.yMin ?
edge.end_pos.y : cbox.yMin;
cbox.yMax = edge.end_pos.y > cbox.yMax ?
edge.end_pos.y : cbox.yMax;
break;
}
default:
break;
}
return cbox;
}
/* The function returns the orientation for a single contour. */
/* Note that the orientation is independent of the fill rule. */
/* So, for ttf the clockwise has to be filled and the opposite */
/* for otf fonts. */
static SDF_Contour_Orientation
get_contour_orientation ( SDF_Contour* contour )
{
SDF_Edge* head = NULL;
FT_26D6 area = 0;
/* return none if invalid parameters */
if ( !contour || !contour->edges )
return SDF_ORIENTATION_NONE;
head = contour->edges;
/* Simply calculate the area of the control box for */
/* all the edges. */
while ( head )
{
switch ( head->edge_type ) {
case SDF_EDGE_LINE:
{
area += MUL_26D6( ( head->end_pos.x - head->start_pos.x ),
( head->end_pos.y + head->start_pos.y ) );
break;
}
case SDF_EDGE_CONIC:
{
area += MUL_26D6( head->control_a.x - head->start_pos.x,
head->control_a.y + head->start_pos.y );
area += MUL_26D6( head->end_pos.x - head->control_a.x,
head->end_pos.y + head->control_a.y );
break;
}
case SDF_EDGE_CUBIC:
{
area += MUL_26D6( head->control_a.x - head->start_pos.x,
head->control_a.y + head->start_pos.y );
area += MUL_26D6( head->control_b.x - head->control_a.x,
head->control_b.y + head->control_a.y );
area += MUL_26D6( head->end_pos.x - head->control_b.x,
head->end_pos.y + head->control_b.y );
break;
}
default:
return SDF_ORIENTATION_NONE;
}
head = head->next;
}
/* Clockwise contour cover a positive area, and Anti-Clockwise */
/* contour cover a negitive area. */
if ( area > 0 )
return SDF_ORIENTATION_CW;
else
return SDF_ORIENTATION_ACW;
}
/* The function is exactly same as the one */
/* in the smooth renderer. It splits a conic */
/* into two conic exactly half way at t = 0.5 */
static void
split_conic( FT_26D6_Vec* base )
{
FT_26D6 a, b;
base[4].x = base[2].x;
a = base[0].x + base[1].x;
b = base[1].x + base[2].x;
base[3].x = b / 2;
base[2].x = ( a + b ) / 4;
base[1].x = a / 2;
base[4].y = base[2].y;
a = base[0].y + base[1].y;
b = base[1].y + base[2].y;
base[3].y = b / 2;
base[2].y = ( a + b ) / 4;
base[1].y = a / 2;
}
/* The function is exactly same as the one */
/* in the smooth renderer. It splits a cubic */
/* into two cubic exactly half way at t = 0.5 */
static void
split_cubic( FT_26D6_Vec* base )
{
FT_26D6 a, b, c;
base[6].x = base[3].x;
a = base[0].x + base[1].x;
b = base[1].x + base[2].x;
c = base[2].x + base[3].x;
base[5].x = c / 2;
c += b;
base[4].x = c / 4;
base[1].x = a / 2;
a += b;
base[2].x = a / 4;
base[3].x = ( a + c ) / 8;
base[6].y = base[3].y;
a = base[0].y + base[1].y;
b = base[1].y + base[2].y;
c = base[2].y + base[3].y;
base[5].y = c / 2;
c += b;
base[4].y = c / 4;
base[1].y = a / 2;
a += b;
base[2].y = a / 4;
base[3].y = ( a + c ) / 8;
}
/* the function splits a conic bezier curve */
/* into a number of lines and adds them to */
/* a list `out'. The function uses recursion */
/* that is why a `max_splits' param is required */
/* for stopping. */
static FT_Error
split_sdf_conic( FT_Memory memory,
FT_26D6_Vec* control_points,
FT_Int max_splits,
SDF_Edge** out )
{
FT_Error error = FT_Err_Ok;
FT_26D6_Vec cpos[5];
SDF_Edge* left,* right;
if ( !memory || !out )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
/* split the conic */
cpos[0] = control_points[0];
cpos[1] = control_points[1];
cpos[2] = control_points[2];
split_conic( cpos );
/* If max number of splits is done */
/* then stop and add the lines to */
/* the list. */
if ( max_splits <= 2 )
goto Append;
/* If not max splits then keep splitting */
FT_CALL( split_sdf_conic( memory, &cpos[0], max_splits / 2, out ) );
FT_CALL( split_sdf_conic( memory, &cpos[2], max_splits / 2, out ) );
/* [NOTE]: This is not an efficient way of */
/* splitting the curve. Check the deviation */
/* instead and stop if the deviation is less */
/* than a pixel. */
goto Exit;
Append:
/* Allocation and add the lines to the list. */
FT_CALL( sdf_edge_new( memory, &left) );
FT_CALL( sdf_edge_new( memory, &right) );
left->start_pos = cpos[0];
left->end_pos = cpos[2];
left->edge_type = SDF_EDGE_LINE;
right->start_pos = cpos[2];
right->end_pos = cpos[4];
right->edge_type = SDF_EDGE_LINE;
left->next = right;
right->next = (*out);
*out = left;
Exit:
return error;
}
/* the function splits a cubic bezier curve */
/* into a number of lines and adds them to */
/* a list `out'. The function uses recursion */
/* that is why a `max_splits' param is required */
/* for stopping. */
static FT_Error
split_sdf_cubic( FT_Memory memory,
FT_26D6_Vec* control_points,
FT_Int max_splits,
SDF_Edge** out )
{
FT_Error error = FT_Err_Ok;
FT_26D6_Vec cpos[7];
SDF_Edge* left,* right;
if ( !memory || !out )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
/* split the conic */
cpos[0] = control_points[0];
cpos[1] = control_points[1];
cpos[2] = control_points[2];
cpos[3] = control_points[3];
split_cubic( cpos );
/* If max number of splits is done */
/* then stop and add the lines to */
/* the list. */
if ( max_splits <= 2 )
goto Append;
/* If not max splits then keep splitting */
FT_CALL( split_sdf_cubic( memory, &cpos[0], max_splits / 2, out ) );
FT_CALL( split_sdf_cubic( memory, &cpos[3], max_splits / 2, out ) );
/* [NOTE]: This is not an efficient way of */
/* splitting the curve. Check the deviation */
/* instead and stop if the deviation is less */
/* than a pixel. */
goto Exit;
Append:
/* Allocation and add the lines to the list. */
FT_CALL( sdf_edge_new( memory, &left) );
FT_CALL( sdf_edge_new( memory, &right) );
left->start_pos = cpos[0];
left->end_pos = cpos[3];
left->edge_type = SDF_EDGE_LINE;
right->start_pos = cpos[3];
right->end_pos = cpos[6];
right->edge_type = SDF_EDGE_LINE;
left->next = right;
right->next = (*out);
*out = left;
Exit:
return error;
}
/* This function subdivide and entire shape */
/* into line segment such that it doesn't */
/* look visually different from the original */
/* curve. */
static FT_Error
split_sdf_shape( SDF_Shape* shape )
{
FT_Error error = FT_Err_Ok;
FT_Memory memory;
SDF_Contour* contours;
SDF_Contour* new_contours = NULL;
if ( !shape || !shape->memory )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
contours = shape->contours;
memory = shape->memory;
/* for each contour */
while ( contours )
{
SDF_Edge* edges = contours->edges;
SDF_Edge* new_edges = NULL;
SDF_Contour* tempc;
/* for each edge */
while ( edges )
{
SDF_Edge* edge = edges;
SDF_Edge* temp;
switch ( edge->edge_type )
{
case SDF_EDGE_LINE:
{
/* Just create a duplicate edge in case */
/* it is a line. We can use the same edge. */
FT_CALL( sdf_edge_new( memory, &temp ) );
ft_memcpy( temp, edge, sizeof( *edge ) );
temp->next = new_edges;
new_edges = temp;
break;
}
case SDF_EDGE_CONIC:
{
/* Subdivide the curve and add to the list. */
FT_26D6_Vec ctrls[3];
ctrls[0] = edge->start_pos;
ctrls[1] = edge->control_a;
ctrls[2] = edge->end_pos;
error = split_sdf_conic( memory, ctrls, 32, &new_edges );
break;
}
case SDF_EDGE_CUBIC:
{
/* Subdivide the curve and add to the list. */
FT_26D6_Vec ctrls[4];
ctrls[0] = edge->start_pos;
ctrls[1] = edge->control_a;
ctrls[2] = edge->control_b;
ctrls[3] = edge->end_pos;
error = split_sdf_cubic( memory, ctrls, 32, &new_edges );
break;
}
default:
error = FT_THROW( Invalid_Argument );
goto Exit;
}
edges = edges->next;
}
/* add to the contours list */
FT_CALL( sdf_contour_new( memory, &tempc ) );
tempc->next = new_contours;
tempc->edges = new_edges;
new_contours = tempc;
new_edges = NULL;
/* deallocate the contour */
tempc = contours;
contours = contours->next;
sdf_contour_done( memory, &tempc );
}
shape->contours = new_contours;
Exit:
return error;
}
/* END */
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