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[sdf] Added basic outline of the functions required to generate sdf.

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Anuj Verma 2020-06-28 10:10:15 +05:30 committed by anujverma
parent 6d4e00ae37
commit e9fce03032
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21
[GSoC]ChangeLog
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@ -1,3 +1,24 @@
2020-06-27 Anuj Verma <anujv@iitbhilai.ac.in>
[sdf] Added basic outline of the functions required to
generate sdf.
* src/sdf/ftsdf.c (SDF_Signed_Distance): Added struct which
represent a complete signed distance and can be used to
get cross, dot, sign etc.
* src/sdf/ftsdf.c (SDF_Iterator_IO): This struct will be used
while `FT_List_Iterate'.
* src/sdf/ftsdf.c (sdf_generate): Added function which genearte
SDF from `SDF_Shape'.
* src/sdf/ftsdf.c (sdf_edge_iterator_func,
sdf_contour_iterator_func): Added funcions
which iterate through contours and edges and return the shortest
distance.
2020-06-26 Anuj Verma <anujv@iitbhilai.ac.in>
[sdf] Added `SDF_Raster_Params' struct which extends

215
src/sdf/ftsdf.c
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@ -6,6 +6,14 @@
#include "ftsdferrs.h"
/**************************************************************************
*
* macros
*
*/
#define FT_INT_26D6( x ) ( x * 64 ) /* convert int to 26.6 fixed point */
/**************************************************************************
*
* typedefs
@ -15,6 +23,8 @@
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 */
/**************************************************************************
*
* structures and enums
@ -67,6 +77,40 @@
} SDF_Shape;
typedef struct SDF_Signed_Distance_
{
/* Nearest point the outline to a given point. */
/* [note]: This is not a *direction* vector, this */
/* simply a *point* vector on the grid. */
FT_16D16_Vec neartest_point;
/* The normalized direction of the curve at the */
/* above point. */
/* [note]: This is a *direction* vector. */
FT_16D16_Vec direction;
/* Unsigned shortest distance from the point to */
/* the above `nearest_point'. */
FT_16D16 distance;
/* Represent weather the `nearest_point' 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;
/* This struct servers as both input and output while */
/* iterating through the contours and edges. */
typedef struct SDF_Iterator_IO_
{
FT_26D6_Vec current_point; /* input */
SDF_Signed_Distance shortest_point; /* output */
} SDF_Iterator_IO;
/**************************************************************************
*
* constants, initializer and destructor
@ -87,6 +131,10 @@
static
const SDF_Shape null_shape = { NULL, { NULL, NULL } };
static
const SDF_Signed_Distance max_sdf_dist = { { 0, 0 }, { 0, 0 },
FT_INT_MAX, 0 };
/* Creates a new `SDF_Edge' on the heap and assigns the `edge' */
/* pointer to the newly allocated memory. */
static FT_Error
@ -547,6 +595,173 @@
#endif
/*************************************************************************/
/*************************************************************************/
/** **/
/** RASTERIZER **/
/** **/
/*************************************************************************/
/*************************************************************************/
/**************************************************************************
*
* @Function:
* sdf_edge_iterator_func
*
* @Description:
* This function find the shortest distance from a point to
* a given point. The function assign the output if current edge
* distance is smaller than the output. Make sure to assign max
* distance to io.shortest_point before calling the iterator first
* time.
*
* @Input:
* [TODO]
*
* @Return:
* [TODO]
*/
static FT_Error
sdf_edge_iterator_func( FT_ListNode node,
void* user )
{
FT_Error error = FT_Err_Ok;
SDF_Iterator_IO* io = (SDF_Iterator_IO*)user;
if ( !node || !user )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
Exit:
return error;
}
/**************************************************************************
*
* @Function:
* sdf_contour_iterator_func
*
* @Description:
* This function iterate through all the edges that make up
* the contour and find the shortest distance from a point to
* this contour. The function assign the output if any edge distance
* is smaller than the output. Make sure to assign max distance to
* io.shortest_point before calling the iterator for the first time.
*
* @Input:
* [TODO]
*
* @Return:
* [TODO]
*/
static FT_Error
sdf_contour_iterator_func( FT_ListNode node,
void* user )
{
FT_Error error = FT_Err_Ok;
SDF_Iterator_IO* io = (SDF_Iterator_IO*)user;
if ( !node || !user )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
Exit:
return error;
}
/**************************************************************************
*
* @Function:
* sdf_generate
*
* @Description:
* This is the main function that is responsible for generating
* signed distance fields. The function will not align or compute
* the size of the `bitmap', therefore setup the `bitmap' properly
* and transform the `shape' appropriately before calling this
* function.
* Currently we check all the pixels against all the contours and
* all the edges.
*
* @Input:
* [TODO]
*
* @Return:
* [TODO]
*/
static FT_Error
sdf_generate( const SDF_Shape* shape,
FT_UInt spread,
FT_Bitmap* bitmap )
{
FT_Error error = FT_Err_Ok;
FT_UInt width = 0;
FT_UInt rows = 0;
FT_UInt x = 0; /* used to loop in x direction i.e. width */
FT_UInt y = 0; /* used to loop in y direction i.e. rows */
if ( !shape || !bitmap )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
if ( spread < MIN_SPREAD || spread > MAX_SPREAD )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
width = bitmap->width;
rows = bitmap->rows;
if ( width == 0 || rows == 0 )
{
FT_TRACE0(( "[sdf] sdf_generate:\n"
" Cannot render glyph with width/height == 0\n"
" (width, height provided [%d, %d])", width, rows ));
error = FT_THROW( Cannot_Render_Glyph );
goto Exit;
}
/* loop through all the rows */
for ( y = 0; y < rows; y++ )
{
/* loop through all the pixels of a row */
for ( x = 0; x < width; x++ )
{
/* `grid_point' is the current pixel position */
/* our task is to find the shortest distance */
/* from this point to the entire shape. */
FT_26D6_Vec grid_point = { FT_INT_26D6( x ),
FT_INT_26D6( y ) };
SDF_Iterator_IO arg;
/* This `grid_point' is at the corner, but we */
/* use the center of the pixel. */
grid_point.x += FT_INT_26D6( 1 ) / 2;
grid_point.y += FT_INT_26D6( 1 ) / 2;
arg.current_point = grid_point;
arg.shortest_point = max_sdf_dist;
/* [TODO]: iterate through all the contours */
/* [TODO]: Now check the returned distance and assign */
/* the values to the bitmap. */
}
}
Exit:
return FT_THROW( Unimplemented_Feature );
}
/**************************************************************************
*
* interface functions