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[sdf, bsdf] Added better documentation.

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* src/sdf/ftsdf.c, src/sdf/ftbsdf.c (*): Added documentation
  of the structs and enums for both the renderers.
This commit is contained in:
Anuj Verma 2020-08-07 16:47:50 +05:30
parent 06bbff76b9
commit 307b0cbd6f
3 changed files with 292 additions and 56 deletions
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7
[GSoC]ChangeLog
View File

@ -1,3 +1,10 @@
2020-08-7 Anuj Verma <anujv@iitbhilai.ac.in>
[sdf, bsdf] Added better documentation.
* src/sdf/ftsdf.c, src/sdf/ftbsdf.c (*): Added documentation
of the structs and enums for both the renderers.
2020-08-6 Anuj Verma <anujv@iitbhilai.ac.in>
[sdf] Added function to get contour orientation.

82
src/sdf/ftbsdf.c
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@ -22,22 +22,87 @@
*
*/
/**************************************************************************
*
* @Struct:
* BSDF_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 BSDF_TRaster_
{
FT_Memory memory; /* used internally to allocate memory */
FT_Memory memory;
} BSDF_TRaster;
/* Euclidean distance used for euclidean distance transform */
/* can also be interpreted as edge distance. */
/**************************************************************************
*
* @Struct:
* ED
*
* @Description:
* Euclidean distance used for euclidean distance transform can also be
* interpreted as edge distance.
*
* @Fields:
* dist ::
* Vector length of the `near' parameter. Can be squared or absolute
* depending on the `USE_SQUARED_DISTANCES' parameter defined in
* `ftsdfcommon.h'.
*
* near ::
* Vector to the nearest edge. Can also be interpreted as shortest
* distance of a point.
*
* alpha ::
* Alpha value of the original bitmap from which we generate SDF.
* While computing the gradient and determining the proper sign
* of a pixel this field is used.
*
*/
typedef struct ED_
{
FT_16D16 dist; /* distance at `near' */
FT_16D16_Vec near; /* nearest point */
FT_Byte alpha; /* alpha of the source */
FT_16D16 dist;
FT_16D16_Vec near;
FT_Byte alpha;
} ED;
/**************************************************************************
*
* @Struct:
* BSDF_Worker
*
* @Description:
* Just a convenient struct which is passed to most of the functions
* while generating SDF. This makes it easier to pass parameters because
* most functions require the same parameters.
*
* @Fields:
* distance_map ::
* A 1D array which is interpreted as 2D array. This array contains
* the Euclidean distance of all the points of the bitmap.
*
* width ::
* Width of the above `distance_map'.
*
* rows ::
* Number of rows in the above `distance_map'.
*
* params ::
* Internal params and properties required by the rasterizer. See
* `ftsdf.h' for the fields of this struct.
*
*/
typedef struct BSDF_Worker_
{
ED* distance_map;
@ -977,6 +1042,7 @@
*
*/
/* called when adding a new module through `FT_Add_Module' */
static FT_Error
bsdf_raster_new( FT_Memory memory,
FT_Raster* araster)
@ -995,6 +1061,7 @@
return error;
}
/* unused */
static void
bsdf_raster_reset( FT_Raster raster,
unsigned char* pool_base,
@ -1006,6 +1073,7 @@
FT_UNUSED( pool_size );
}
/* unused */
static FT_Error
bsdf_raster_set_mode( FT_Raster raster,
unsigned long mode,
@ -1019,6 +1087,7 @@
return FT_Err_Ok;
}
/* called while rendering through `FT_Render_Glyph' */
static FT_Error
bsdf_raster_render( FT_Raster raster,
const FT_Raster_Params* params )
@ -1112,6 +1181,7 @@
return error;
}
/* called while deleting a `FT_Library' only if the module is added */
static void
bsdf_raster_done( FT_Raster raster )
{

259
src/sdf/ftsdf.c
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@ -143,6 +143,8 @@
/* then they will be checked for corner if they have ambiguity. */
#define CORNER_CHECK_EPSILON 32
/* Coarse grid dimension. Probably will be removed in the future cause */
/* coarse grid optimization is the slowest. */
#define CG_DIMEN 8
/**************************************************************************
@ -161,101 +163,258 @@
*
*/
/**************************************************************************
*
* @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; /* used internally to allocate memory */
FT_Memory memory;
} SDF_TRaster;
/* enumeration of all the types of curve present in vector fonts */
/**************************************************************************
*
* @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, /* undefined, used to initialize */
SDF_EDGE_LINE = 1, /* straight line segment */
SDF_EDGE_CONIC = 2, /* second order bezier curve */
SDF_EDGE_CUBIC = 3 /* third order bezier curve */
SDF_EDGE_UNDEFINED = 0,
SDF_EDGE_LINE = 1,
SDF_EDGE_CONIC = 2,
SDF_EDGE_CUBIC = 3
} SDF_Edge_Type;
/* Enumeration for the orientation of a contour, remember */
/* the orientation is independent of the fill rule. */
/**************************************************************************
*
* @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, /* undefined, used to initialize */
SDF_ORIENTATION_CW = 0, /* clockwise orientation */
SDF_ORIENTATION_ACW = 0, /* anti-clockwise orientation */
SDF_ORIENTATION_NONE = 0,
SDF_ORIENTATION_CW = 0,
SDF_ORIENTATION_ACW = 0
} SDF_Contour_Orientation;
/* represent a single edge in a contour */
/**************************************************************************
*
* @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; /* start position of the edge */
FT_26D6_Vec end_pos; /* end position of the edge */
FT_26D6_Vec control_a; /* first control point of a bezier curve */
FT_26D6_Vec control_b; /* second control point of a bezier curve */
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; /* edge identifier */
SDF_Edge_Type edge_type;
struct SDF_Edge_* next; /* to create linked list */
struct SDF_Edge_* next;
} SDF_Edge;
/* A contour represent a set of edges which make a closed */
/* loop. */
/**************************************************************************
*
* @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; /* end position of the last edge */
SDF_Edge* edges; /* list of all edges in the contour */
FT_26D6_Vec last_pos;
SDF_Edge* edges;
struct SDF_Contour_* next; /* to create linked list */
struct SDF_Contour_* next;
} SDF_Contour;
/* Represent a set a contours which makes up a complete */
/* glyph outline. */
/**************************************************************************
*
* @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; /* used internally to allocate memory */
SDF_Contour* contours; /* list of all contours in the outline */
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_
{
/* Unsigned shortest distance from the point to */
/* the above `nearest_point'. */
/* [NOTE]: This can represent both squared as or */
/* actual distance. This is controlled by the */
/* `USE_SQUARED_DISTANCES' macro. */
FT_16D16 distance;
/* The cross product of distance vector and the */
/* direction. ( aka orthogonality ) */
FT_16D16 cross;
/* Represent weather the distance vector is outside */
/* or inside the contour corresponding to the edge. */
/* [note]: This sign may or may not be correct, */
/* therefore it must be checked properly in */
/* case there is an ambiguity. */
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.
*
*/
typedef struct SDF_Params_
{
/* Used to properly assign sign to the pixels. In */
/* truetype the right should be inside but in post */
/* script left should be inside. */
FT_Orientation orientation;
/* Simply flip the sign if this is true. */
FT_Bool flip_sign;
/* If set to true the output will be upside down. */
/* Can be useful because OpenGL and DirectX have */
/* different coordinate system for textures. */
FT_Bool flip_y;
} SDF_Params;