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[sdf] Added basic overlapping contour support. 

* src/sdf/ftsdf.c (sdf_generate_with_overlaps): New function.
(sdf_raster_render): Enable it.
This commit is contained in:
Anuj Verma 2020-08-20 07:54:13 +05:30 committed by Werner Lemberg
parent 879ca87f0b
commit 05f6088df3
2 changed files with 259 additions and 6 deletions
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7
ChangeLog
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@ -1,3 +1,10 @@
2020-08-20 Anuj Verma <anujv@iitbhilai.ac.in>
[sdf] Added basic overlapping contour support.
* src/sdf/ftsdf.c (sdf_generate_with_overlaps): New function.
(sdf_raster_render): Enable it.
2020-08-19 Anuj Verma <anujv@iitbhilai.ac.in>
[sdf] Add build infrastructure.

258
src/sdf/ftsdf.c
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@ -436,7 +436,7 @@
* orientation ::
* This is not the @SDF_Contour_Orientation value but @FT_Orientation,
* which determines whether clockwise-oriented outlines are to be
* filled or anti-clockwise-oriented ones.
* filled or counter-clockwise-oriented ones.
*
* flip_sign ::
* If set to true, flip the sign. By default the points filled by the
@ -996,8 +996,8 @@
head = head->next;
}
/* Clockwise contours cover a positive area, and anti-clockwise */
/* contours cover a negative area. */
/* Clockwise contours cover a positive area, and counter-clockwise */
/* contours cover a negative area. */
if ( area > 0 )
return SDF_ORIENTATION_CW;
else
@ -3353,6 +3353,255 @@
}
/**************************************************************************
*
* @Function:
* sdf_generate_with_overlaps
*
* @Description:
* This function can be used to generate SDF for glyphs with overlapping
* contours. The function generates SDF for contours separately on
* separate bitmaps (to generate SDF it uses
* `sdf_generate_subdivision`). At the end it simply combines all the
* SDF into the output bitmap; this fixes all the signs and removes
* overlaps.
*
* @Input:
* internal_params ::
* Internal parameters and properties required by the rasterizer. See
* @SDF_Params for more.
*
* shape ::
* A complete shape which is used to generate SDF.
*
* spread ::
* Maximum distances to be allowed in the output bitmap.
*
* @Output:
* bitmap ::
* The output bitmap which will contain the SDF information.
*
* @Return:
* FreeType error, 0 means success.
*
* @Note:
* The function cannot generate a proper SDF for glyphs with
* self-intersecting contours because we cannot separate them into two
* separate bitmaps. In case of self-intersecting contours it is
* necessary to remove the overlaps before generating the SDF.
*
*/
static FT_Error
sdf_generate_with_overlaps( SDF_Params internal_params,
SDF_Shape* shape,
FT_UInt spread,
const FT_Bitmap* bitmap )
{
FT_Error error = FT_Err_Ok;
FT_Int num_contours; /* total number of contours */
FT_Int i, j; /* iterators */
FT_Int width, rows; /* width and rows of the bitmap */
FT_Bitmap* bitmaps; /* separate bitmaps for contours */
SDF_Contour* contour; /* temporary variable to iterate */
SDF_Contour* temp_contour; /* temporary contour */
SDF_Contour* head; /* head of the contour list */
SDF_Shape temp_shape; /* temporary shape */
FT_Memory memory; /* to allocate memory */
FT_6D10* t; /* target bitmap buffer */
FT_Bool flip_sign; /* filp sign? */
/* orientation of all the separate contours */
SDF_Contour_Orientation* orientations;
bitmaps = NULL;
orientations = NULL;
head = NULL;
if ( !shape || !bitmap || !shape->memory )
{
error = FT_THROW( Invalid_Argument );
goto Exit;
}
contour = shape->contours;
memory = shape->memory;
temp_shape.memory = memory;
width = (FT_Int)bitmap->width;
rows = (FT_Int)bitmap->rows;
num_contours = 0;
/* find the number of contours in the shape */
while ( contour )
{
num_contours++;
contour = contour->next;
}
/* allocate the bitmaps to generate SDF for separate contours */
if ( SDF_ALLOC( bitmaps, num_contours * sizeof ( *bitmaps ) ) )
goto Exit;
/* zero the memory */
ft_memset( bitmaps, 0, num_contours * sizeof ( *bitmaps ) );
/* allocate array to hold orientation for all contours */
if ( SDF_ALLOC( orientations, num_contours * sizeof ( *orientations ) ) )
goto Exit;
/* zero the memory */
ft_memset( orientations, 0, num_contours * sizeof ( *orientations ) );
/* Disable `flip_sign` to avoid extra complication */
/* during the combination phase. */
flip_sign = internal_params.flip_sign;
internal_params.flip_sign = 0;
contour = shape->contours;
/* Iterate over all contours and generate SDF separately. */
for ( i = 0; i < num_contours; i++ )
{
/* initialize the corresponding bitmap */
FT_Bitmap_Init( &bitmaps[i] );
bitmaps[i].width = bitmap->width;
bitmaps[i].rows = bitmap->rows;
bitmaps[i].pitch = bitmap->pitch;
bitmaps[i].num_grays = bitmap->num_grays;
bitmaps[i].pixel_mode = bitmap->pixel_mode;
/* allocate memory for the buffer */
if ( SDF_ALLOC( bitmaps[i].buffer, bitmap->rows * bitmap->pitch ) )
goto Exit;
/* determine the orientation */
orientations[i] = get_contour_orientation( contour );
/* The `overload_sign` property is specific to */
/* `sdf_generate_bounding_box`. This basically */
/* overloads the default sign of the outside */
/* pixels, which is necessary for */
/* counter-clockwise contours. */
if ( orientations[i] == SDF_ORIENTATION_ACW &&
internal_params.orientation == FT_ORIENTATION_FILL_RIGHT )
internal_params.overload_sign = 1;
else if ( orientations[i] == SDF_ORIENTATION_CW &&
internal_params.orientation == FT_ORIENTATION_FILL_LEFT )
internal_params.overload_sign = 1;
else
internal_params.overload_sign = 0;
/* Make `contour->next` NULL so that there is */
/* one contour in the list. Also hold the next */
/* contour in a temporary variable so as to */
/* restore the original value. */
temp_contour = contour->next;
contour->next = NULL;
/* Use `temp_shape` to hold the new contour. */
/* Now, `temp_shape` has only one contour. */
temp_shape.contours = contour;
/* finally generate the SDF */
FT_CALL( sdf_generate_subdivision( internal_params,
&temp_shape,
spread,
&bitmaps[i] ) );
/* Restore the original `next` variable. */
contour->next = temp_contour;
/* Since `split_sdf_shape` deallocated the original */
/* contours list we need to assign the new value to */
/* the shape's contour. */
temp_shape.contours->next = head;
head = temp_shape.contours;
/* Simply flip the orientation in case of post-script fonts */
/* so as to avoid modificatons in the combining phase. */
if ( internal_params.orientation == FT_ORIENTATION_FILL_LEFT )
{
if ( orientations[i] == SDF_ORIENTATION_CW )
orientations[i] = SDF_ORIENTATION_ACW;
else if ( orientations[i] == SDF_ORIENTATION_ACW )
orientations[i] = SDF_ORIENTATION_CW;
}
contour = contour->next;
}
/* assign the new contour list to `shape->contours` */
shape->contours = head;
/* cast the output bitmap buffer */
t = (FT_6D10*)bitmap->buffer;
/* Iterate over all pixels and combine all separate */
/* contours. These are the rules for combining: */
/* */
/* (1) For all clockwise contours, compute the largest */
/* value. Name this as `val_c`. */
/* (2) For all counter-clockwise contours, compute the */
/* smallest value. Name this as `val_ac`. */
/* (3) Now, finally use the smaller value of `val_c' */
/* and `val_ac'. */
for ( j = 0; j < rows; j++ )
{
for ( i = 0; i < width; i++ )
{
FT_Int id = j * width + i; /* index of current pixel */
FT_Int c; /* contour iterator */
FT_6D10 val_c = SHRT_MIN; /* max clockwise value */
FT_6D10 val_ac = SHRT_MAX; /* min counter-clockwise val */
/* iterate through all the contours */
for ( c = 0; c < num_contours; c++ )
{
/* current contour value */
FT_6D10 temp = ((FT_6D10*)bitmaps[c].buffer)[id];
if ( orientations[c] == SDF_ORIENTATION_CW )
val_c = FT_MAX( val_c, temp ); /* clockwise */
else
val_ac = FT_MIN( val_ac, temp ); /* counter-clockwise */
}
/* Finally find the smaller of the two and assign to output. */
/* Also apply `flip_sign` if set. */
t[id] = FT_MIN( val_c, val_ac ) * ( flip_sign ? -1 : 1 );
}
}
Exit:
/* deallocate orientations array */
if ( orientations )
SDF_FREE( orientations );
/* deallocate temporary bitmaps */
if ( bitmaps )
{
if ( num_contours == 0 )
error = FT_THROW( Raster_Corrupted );
else
{
for ( i = 0; i < num_contours; i++ )
SDF_FREE( bitmaps[i].buffer );
SDF_FREE( bitmaps );
}
}
return error;
}
/**************************************************************************
*
* interface functions
@ -3497,14 +3746,11 @@
FT_CALL( sdf_outline_decompose( outline, shape ) );
#if 0
/* XXX to be added */
if ( sdf_params->overlaps )
FT_CALL( sdf_generate_with_overlaps( internal_params,
shape, sdf_params->spread,
sdf_params->root.target ) );
else
#endif
FT_CALL( sdf_generate_subdivision( internal_params,
shape, sdf_params->spread,
sdf_params->root.target ) );