/***************************************************************************/
/* */
/* ftgrays.c */
/* */
/* A new `perfect' anti-aliasing renderer (body). */
/* */
/* Copyright 2000-2003, 2005-2014 by */
/* David Turner, Robert Wilhelm, and Werner Lemberg. */
/* */
/* This file is part of the FreeType project, and may only be used, */
/* modified, and distributed under the terms of the FreeType project */
/* license, LICENSE.TXT. By continuing to use, modify, or distribute */
/* this file you indicate that you have read the license and */
/* understand and accept it fully. */
/* */
/***************************************************************************/
/*************************************************************************/
/* */
/* This is a new anti-aliasing scan-converter for FreeType 2. The */
/* algorithm used here is _very_ different from the one in the standard */
/* `ftraster' module. Actually, `ftgrays' computes the _exact_ */
/* coverage of the outline on each pixel cell. */
/* */
/* It is based on ideas that I initially found in Raph Levien's */
/* excellent LibArt graphics library (see http://www.levien.com/libart */
/* for more information, though the web pages do not tell anything */
/* about the renderer; you'll have to dive into the source code to */
/* understand how it works). */
/* */
/* Note, however, that this is a _very_ different implementation */
/* compared to Raph's. Coverage information is stored in a very */
/* different way, and I don't use sorted vector paths. Also, it doesn't */
/* use floating point values. */
/* */
/* This renderer has the following advantages: */
/* */
/* - It doesn't need an intermediate bitmap. Instead, one can supply a */
/* callback function that will be called by the renderer to draw gray */
/* spans on any target surface. You can thus do direct composition on */
/* any kind of bitmap, provided that you give the renderer the right */
/* callback. */
/* */
/* - A perfect anti-aliaser, i.e., it computes the _exact_ coverage on */
/* each pixel cell. */
/* */
/* - It performs a single pass on the outline (the `standard' FT2 */
/* renderer makes two passes). */
/* */
/* - It can easily be modified to render to _any_ number of gray levels */
/* cheaply. */
/* */
/* - For small (< 20) pixel sizes, it is faster than the standard */
/* renderer. */
/* */
/*************************************************************************/
#include "plutovg-ft-raster.h"
#include "plutovg-ft-math.h"
#define PVG_FT_BEGIN_STMNT do {
#define PVG_FT_END_STMNT } while ( 0 )
#include <setjmp.h>
#define pvg_ft_setjmp setjmp
#define pvg_ft_longjmp longjmp
#define pvg_ft_jmp_buf jmp_buf
#include <stddef.h>
typedef ptrdiff_t PVG_FT_PtrDist;
#define ErrRaster_Invalid_Mode -2
#define ErrRaster_Invalid_Outline -1
#define ErrRaster_Invalid_Argument -3
#define ErrRaster_Memory_Overflow -4
#define ErrRaster_OutOfMemory -6
#include <stdlib.h>
#include <limits.h>
#define PVG_FT_MINIMUM_POOL_SIZE 8192
#define RAS_ARG PWorker worker
#define RAS_ARG_ PWorker worker,
#define RAS_VAR worker
#define RAS_VAR_ worker,
#define ras (*worker)
/* must be at least 6 bits! */
#define PIXEL_BITS 8
#define ONE_PIXEL ( 1L << PIXEL_BITS )
#define TRUNC( x ) (TCoord)( (x) >> PIXEL_BITS )
#define FRACT( x ) (TCoord)( (x) & ( ONE_PIXEL - 1 ) )
#if PIXEL_BITS >= 6
#define UPSCALE( x ) ( (x) * ( ONE_PIXEL >> 6 ) )
#define DOWNSCALE( x ) ( (x) >> ( PIXEL_BITS - 6 ) )
#else
#define UPSCALE( x ) ( (x) >> ( 6 - PIXEL_BITS ) )
#define DOWNSCALE( x ) ( (x) * ( 64 >> PIXEL_BITS ) )
#endif
/* Compute `dividend / divisor' and return both its quotient and */
/* remainder, cast to a specific type. This macro also ensures that */
/* the remainder is always positive. */
#define PVG_FT_DIV_MOD( type, dividend, divisor, quotient, remainder ) \
PVG_FT_BEGIN_STMNT \
(quotient) = (type)( (dividend) / (divisor) ); \
(remainder) = (type)( (dividend) % (divisor) ); \
if ( (remainder) < 0 ) \
{ \
(quotient)--; \
(remainder) += (type)(divisor); \
} \
PVG_FT_END_STMNT
/* These macros speed up repetitive divisions by replacing them */
/* with multiplications and right shifts. */
#define PVG_FT_UDIVPREP( b ) \
long b ## _r = (long)( ULONG_MAX >> PIXEL_BITS ) / ( b )
#define PVG_FT_UDIV( a, b ) \
( ( (unsigned long)( a ) * (unsigned long)( b ## _r ) ) >> \
( sizeof( long ) * CHAR_BIT - PIXEL_BITS ) )
/*************************************************************************/
/* */
/* TYPE DEFINITIONS */
/* */
/* don't change the following types to PVG_FT_Int or PVG_FT_Pos, since we might */
/* need to define them to "float" or "double" when experimenting with */
/* new algorithms */
typedef long TCoord; /* integer scanline/pixel coordinate */
typedef long TPos; /* sub-pixel coordinate */
typedef long TArea ; /* cell areas, coordinate products */
/* maximal number of gray spans in a call to the span callback */
#define PVG_FT_MAX_GRAY_SPANS 256
typedef struct TCell_* PCell;
typedef struct TCell_
{
int x;
int cover;
TArea area;
PCell next;
} TCell;
typedef struct TWorker_
{
TCoord ex, ey;
TPos min_ex, max_ex;
TPos min_ey, max_ey;
TPos count_ex, count_ey;
TArea area;
int cover;
int invalid;
PCell cells;
PVG_FT_PtrDist max_cells;
PVG_FT_PtrDist num_cells;
TPos x, y;
PVG_FT_Outline outline;
PVG_FT_BBox clip_box;
PVG_FT_Span gray_spans[PVG_FT_MAX_GRAY_SPANS];
int num_gray_spans;
int skip_spans;
PVG_FT_Raster_Span_Func render_span;
void* render_span_data;
int band_size;
int band_shoot;
pvg_ft_jmp_buf jump_buffer;
void* buffer;
long buffer_size;
PCell* ycells;
TPos ycount;
} TWorker, *PWorker;
/*************************************************************************/
/* */
/* Initialize the cells table. */
/* */
static void
gray_init_cells( RAS_ARG_ void* buffer,
long byte_size )
{
ras.buffer = buffer;
ras.buffer_size = byte_size;
ras.ycells = (PCell*) buffer;
ras.cells = NULL;
ras.max_cells = 0;
ras.num_cells = 0;
ras.area = 0;
ras.cover = 0;
ras.invalid = 1;
}
/*************************************************************************/
/* */
/* Compute the outline bounding box. */
/* */
static void
gray_compute_cbox( RAS_ARG )
{
PVG_FT_Outline* outline = &ras.outline;
PVG_FT_Vector* vec = outline->points;
PVG_FT_Vector* limit = vec + outline->n_points;
if ( outline->n_points <= 0 )
{
ras.min_ex = ras.max_ex = 0;
ras.min_ey = ras.max_ey = 0;
return;
}
ras.min_ex = ras.max_ex = vec->x;
ras.min_ey = ras.max_ey = vec->y;
vec++;
for ( ; vec < limit; vec++ )
{
TPos x = vec->x;
TPos y = vec->y;
if ( x < ras.min_ex ) ras.min_ex = x;
if ( x > ras.max_ex ) ras.max_ex = x;
if ( y < ras.min_ey ) ras.min_ey = y;
if ( y > ras.max_ey ) ras.max_ey = y;
}
/* truncate the bounding box to integer pixels */
ras.min_ex = ras.min_ex >> 6;
ras.min_ey = ras.min_ey >> 6;
ras.max_ex = ( ras.max_ex + 63 ) >> 6;
ras.max_ey = ( ras.max_ey + 63 ) >> 6;
}
/*************************************************************************/
/* */
/* Record the current cell in the table. */
/* */
static PCell
gray_find_cell( RAS_ARG )
{
PCell *pcell, cell;
TPos x = ras.ex;
if ( x > ras.count_ex )
x = ras.count_ex;
pcell = &ras.ycells[ras.ey];
for (;;)
{
cell = *pcell;
if ( cell == NULL || cell->x > x )
break;
if ( cell->x == x )
goto Exit;
pcell = &cell->next;
}
if ( ras.num_cells >= ras.max_cells )
pvg_ft_longjmp( ras.jump_buffer, 1 );
cell = ras.cells + ras.num_cells++;
cell->x = x;
cell->area = 0;
cell->cover = 0;
cell->next = *pcell;
*pcell = cell;
Exit:
return cell;
}
static void
gray_record_cell( RAS_ARG )
{
if ( ras.area | ras.cover )
{
PCell cell = gray_find_cell( RAS_VAR );
cell->area += ras.area;
cell->cover += ras.cover;
}
}
/*************************************************************************/
/* */
/* Set the current cell to a new position. */
/* */
static void
gray_set_cell( RAS_ARG_ TCoord ex,
TCoord ey )
{
/* Move the cell pointer to a new position. We set the `invalid' */
/* flag to indicate that the cell isn't part of those we're interested */
/* in during the render phase. This means that: */
/* */
/* . the new vertical position must be within min_ey..max_ey-1. */
/* . the new horizontal position must be strictly less than max_ex */
/* */
/* Note that if a cell is to the left of the clipping region, it is */
/* actually set to the (min_ex-1) horizontal position. */
/* All cells that are on the left of the clipping region go to the */
/* min_ex - 1 horizontal position. */
ey -= ras.min_ey;
if ( ex > ras.max_ex )
ex = ras.max_ex;
ex -= ras.min_ex;
if ( ex < 0 )
ex = -1;
/* are we moving to a different cell ? */
if ( ex != ras.ex || ey != ras.ey )
{
/* record the current one if it is valid */
if ( !ras.invalid )
gray_record_cell( RAS_VAR );
ras.area = 0;
ras.cover = 0;
ras.ex = ex;
ras.ey = ey;
}
ras.invalid = ( (unsigned int)ey >= (unsigned int)ras.count_ey ||
ex >= ras.count_ex );
}
/*************************************************************************/
/* */
/* Start a new contour at a given cell. */
/* */
static void
gray_start_cell( RAS_ARG_ TCoord ex,
TCoord ey )
{
if ( ex > ras.max_ex )
ex = (TCoord)( ras.max_ex );
if ( ex < ras.min_ex )
ex = (TCoord)( ras.min_ex - 1 );
ras.area = 0;
ras.cover = 0;
ras.ex = ex - ras.min_ex;
ras.ey = ey - ras.min_ey;
ras.invalid = 0;
gray_set_cell( RAS_VAR_ ex, ey );
}
// The new render-line implementation is not yet used
#if 1
/*************************************************************************/
/* */
/* Render a scanline as one or more cells. */
/* */
static void
gray_render_scanline( RAS_ARG_ TCoord ey,
TPos x1,
TCoord y1,
TPos x2,
TCoord y2 )
{
TCoord ex1, ex2, fx1, fx2, first, dy, delta, mod;
TPos p, dx;
int incr;
ex1 = TRUNC( x1 );
ex2 = TRUNC( x2 );
/* trivial case. Happens often */
if ( y1 == y2 )
{
gray_set_cell( RAS_VAR_ ex2, ey );
return;
}
fx1 = FRACT( x1 );
fx2 = FRACT( x2 );
/* everything is located in a single cell. That is easy! */
/* */
if ( ex1 == ex2 )
goto End;
/* ok, we'll have to render a run of adjacent cells on the same */
/* scanline... */
/* */
dx = x2 - x1;
dy = y2 - y1;
if ( dx > 0 )
{
p = ( ONE_PIXEL - fx1 ) * dy;
first = ONE_PIXEL;
incr = 1;
} else {
p = fx1 * dy;
first = 0;
incr = -1;
dx = -dx;
}
PVG_FT_DIV_MOD( TCoord, p, dx, delta, mod );
ras.area += (TArea)( fx1 + first ) * delta;
ras.cover += delta;
y1 += delta;
ex1 += incr;
gray_set_cell( RAS_VAR_ ex1, ey );
if ( ex1 != ex2 )
{
TCoord lift, rem;
p = ONE_PIXEL * dy;
PVG_FT_DIV_MOD( TCoord, p, dx, lift, rem );
do
{
delta = lift;
mod += rem;
if ( mod >= (TCoord)dx )
{
mod -= (TCoord)dx;
delta++;
}
ras.area += (TArea)( ONE_PIXEL * delta );
ras.cover += delta;
y1 += delta;
ex1 += incr;
gray_set_cell( RAS_VAR_ ex1, ey );
} while ( ex1 != ex2 );
}
fx1 = ONE_PIXEL - first;
End:
dy = y2 - y1;
ras.area += (TArea)( ( fx1 + fx2 ) * dy );
ras.cover += dy;
}
/*************************************************************************/
/* */
/* Render a given line as a series of scanlines. */
/* */
static void
gray_render_line( RAS_ARG_ TPos to_x,
TPos to_y )
{
TCoord ey1, ey2, fy1, fy2, first, delta, mod;
TPos p, dx, dy, x, x2;
int incr;
ey1 = TRUNC( ras.y );
ey2 = TRUNC( to_y ); /* if (ey2 >= ras.max_ey) ey2 = ras.max_ey-1; */
/* perform vertical clipping */
if ( ( ey1 >= ras.max_ey && ey2 >= ras.max_ey ) ||
( ey1 < ras.min_ey && ey2 < ras.min_ey ) )
goto End;
fy1 = FRACT( ras.y );
fy2 = FRACT( to_y );
/* everything is on a single scanline */
if ( ey1 == ey2 )
{
gray_render_scanline( RAS_VAR_ ey1, ras.x, fy1, to_x, fy2 );
goto End;
}
dx = to_x - ras.x;
dy = to_y - ras.y;
/* vertical line - avoid calling gray_render_scanline */
if ( dx == 0 )
{
TCoord ex = TRUNC( ras.x );
TCoord two_fx = FRACT( ras.x ) << 1;
TPos area, max_ey1;
if ( dy > 0)
{
first = ONE_PIXEL;
}
else
{
first = 0;
}
delta = first - fy1;
ras.area += (TArea)two_fx * delta;
ras.cover += delta;
delta = first + first - ONE_PIXEL;
area = (TArea)two_fx * delta;
max_ey1 = ras.count_ey + ras.min_ey;
if (dy < 0) {
if (ey1 > max_ey1) {
ey1 = (max_ey1 > ey2) ? max_ey1 : ey2;
gray_set_cell( &ras, ex, ey1 );
} else {
ey1--;
gray_set_cell( &ras, ex, ey1 );
}
while ( ey1 > ey2 && ey1 >= ras.min_ey)
{
ras.area += area;
ras.cover += delta;
ey1--;
gray_set_cell( &ras, ex, ey1 );
}
if (ey1 != ey2) {
ey1 = ey2;
gray_set_cell( &ras, ex, ey1 );
}
} else {
if (ey1 < ras.min_ey) {
ey1 = (ras.min_ey < ey2) ? ras.min_ey : ey2;
gray_set_cell( &ras, ex, ey1 );
} else {
ey1++;
gray_set_cell( &ras, ex, ey1 );
}
while ( ey1 < ey2 && ey1 < max_ey1)
{
ras.area += area;
ras.cover += delta;
ey1++;
gray_set_cell( &ras, ex, ey1 );
}
if (ey1 != ey2) {
ey1 = ey2;
gray_set_cell( &ras, ex, ey1 );
}
}
delta = (int)( fy2 - ONE_PIXEL + first );
ras.area += (TArea)two_fx * delta;
ras.cover += delta;
goto End;
}
/* ok, we have to render several scanlines */
if ( dy > 0)
{
p = ( ONE_PIXEL - fy1 ) * dx;
first = ONE_PIXEL;
incr = 1;
}
else
{
p = fy1 * dx;
first = 0;
incr = -1;
dy = -dy;
}
/* the fractional part of x-delta is mod/dy. It is essential to */
/* keep track of its accumulation for accurate rendering. */
PVG_FT_DIV_MOD( TCoord, p, dy, delta, mod );
x = ras.x + delta;
gray_render_scanline( RAS_VAR_ ey1, ras.x, fy1, x, (TCoord)first );
ey1 += incr;
gray_set_cell( RAS_VAR_ TRUNC( x ), ey1 );
if ( ey1 != ey2 )
{
TCoord lift, rem;
p = ONE_PIXEL * dx;
PVG_FT_DIV_MOD( TCoord, p, dy, lift, rem );
do
{
delta = lift;
mod += rem;
if ( mod >= (TCoord)dy )
{
mod -= (TCoord)dy;
delta++;
}
x2 = x + delta;
gray_render_scanline( RAS_VAR_ ey1,
x, ONE_PIXEL - first,
x2, first );
x = x2;
ey1 += incr;
gray_set_cell( RAS_VAR_ TRUNC( x ), ey1 );
} while ( ey1 != ey2 );
}
gray_render_scanline( RAS_VAR_ ey1,
x, ONE_PIXEL - first,
to_x, fy2 );
End:
ras.x = to_x;
ras.y = to_y;
}
#else
/*************************************************************************/
/* */
/* Render a straight line across multiple cells in any direction. */
/* */
static void
gray_render_line( RAS_ARG_ TPos to_x,
TPos to_y )
{
TPos dx, dy, fx1, fy1, fx2, fy2;
TCoord ex1, ex2, ey1, ey2;
ex1 = TRUNC( ras.x );
ex2 = TRUNC( to_x );
ey1 = TRUNC( ras.y );
ey2 = TRUNC( to_y );
/* perform vertical clipping */
if ( ( ey1 >= ras.max_ey && ey2 >= ras.max_ey ) ||
( ey1 < ras.min_ey && ey2 < ras.min_ey ) )
goto End;
dx = to_x - ras.x;
dy = to_y - ras.y;
fx1 = FRACT( ras.x );
fy1 = FRACT( ras.y );
if ( ex1 == ex2 && ey1 == ey2 ) /* inside one cell */
;
else if ( dy == 0 ) /* ex1 != ex2 */ /* any horizontal line */
{
ex1 = ex2;
gray_set_cell( RAS_VAR_ ex1, ey1 );
}
else if ( dx == 0 )
{
if ( dy > 0 ) /* vertical line up */
do
{
fy2 = ONE_PIXEL;
ras.cover += ( fy2 - fy1 );
ras.area += ( fy2 - fy1 ) * fx1 * 2;
fy1 = 0;
ey1++;
gray_set_cell( RAS_VAR_ ex1, ey1 );
} while ( ey1 != ey2 );
else /* vertical line down */
do
{
fy2 = 0;
ras.cover += ( fy2 - fy1 );
ras.area += ( fy2 - fy1 ) * fx1 * 2;
fy1 = ONE_PIXEL;
ey1--;
gray_set_cell( RAS_VAR_ ex1, ey1 );
} while ( ey1 != ey2 );
}
else /* any other line */
{
TArea prod = dx * fy1 - dy * fx1;
PVG_FT_UDIVPREP( dx );
PVG_FT_UDIVPREP( dy );
/* The fundamental value `prod' determines which side and the */
/* exact coordinate where the line exits current cell. It is */
/* also easily updated when moving from one cell to the next. */
do
{
if ( prod <= 0 &&
prod - dx * ONE_PIXEL > 0 ) /* left */
{
fx2 = 0;
fy2 = (TPos)PVG_FT_UDIV( -prod, -dx );
prod -= dy * ONE_PIXEL;
ras.cover += ( fy2 - fy1 );
ras.area += ( fy2 - fy1 ) * ( fx1 + fx2 );
fx1 = ONE_PIXEL;
fy1 = fy2;
ex1--;
}
else if ( prod - dx * ONE_PIXEL <= 0 &&
prod - dx * ONE_PIXEL + dy * ONE_PIXEL > 0 ) /* up */
{
prod -= dx * ONE_PIXEL;
fx2 = (TPos)PVG_FT_UDIV( -prod, dy );
fy2 = ONE_PIXEL;
ras.cover += ( fy2 - fy1 );
ras.area += ( fy2 - fy1 ) * ( fx1 + fx2 );
fx1 = fx2;
fy1 = 0;
ey1++;
}
else if ( prod - dx * ONE_PIXEL + dy * ONE_PIXEL <= 0 &&
prod + dy * ONE_PIXEL >= 0 ) /* right */
{
prod += dy * ONE_PIXEL;
fx2 = ONE_PIXEL;
fy2 = (TPos)PVG_FT_UDIV( prod, dx );
ras.cover += ( fy2 - fy1 );
ras.area += ( fy2 - fy1 ) * ( fx1 + fx2 );
fx1 = 0;
fy1 = fy2;
ex1++;
}
else /* ( prod + dy * ONE_PIXEL < 0 &&
prod > 0 ) down */
{
fx2 = (TPos)PVG_FT_UDIV( prod, -dy );
fy2 = 0;
prod += dx * ONE_PIXEL;
ras.cover += ( fy2 - fy1 );
ras.area += ( fy2 - fy1 ) * ( fx1 + fx2 );
fx1 = fx2;
fy1 = ONE_PIXEL;
ey1--;
}
gray_set_cell( RAS_VAR_ ex1, ey1 );
} while ( ex1 != ex2 || ey1 != ey2 );
}
fx2 = FRACT( to_x );
fy2 = FRACT( to_y );
ras.cover += ( fy2 - fy1 );
ras.area += ( fy2 - fy1 ) * ( fx1 + fx2 );
End:
ras.x = to_x;
ras.y = to_y;
}
#endif
static void
gray_split_conic( PVG_FT_Vector* base )
{
TPos a, b;
base[4].x = base[2].x;
b = base[1].x;
a = base[3].x = ( base[2].x + b ) / 2;
b = base[1].x = ( base[0].x + b ) / 2;
base[2].x = ( a + b ) / 2;
base[4].y = base[2].y;
b = base[1].y;
a = base[3].y = ( base[2].y + b ) / 2;
b = base[1].y = ( base[0].y + b ) / 2;
base[2].y = ( a + b ) / 2;
}
static void
gray_render_conic( RAS_ARG_ const PVG_FT_Vector* control,
const PVG_FT_Vector* to )
{
PVG_FT_Vector bez_stack[16 * 2 + 1]; /* enough to accommodate bisections */
PVG_FT_Vector* arc = bez_stack;
TPos dx, dy;
int draw, split;
arc[0].x = UPSCALE( to->x );
arc[0].y = UPSCALE( to->y );
arc[1].x = UPSCALE( control->x );
arc[1].y = UPSCALE( control->y );
arc[2].x = ras.x;
arc[2].y = ras.y;
/* short-cut the arc that crosses the current band */
if ( ( TRUNC( arc[0].y ) >= ras.max_ey &&
TRUNC( arc[1].y ) >= ras.max_ey &&
TRUNC( arc[2].y ) >= ras.max_ey ) ||
( TRUNC( arc[0].y ) < ras.min_ey &&
TRUNC( arc[1].y ) < ras.min_ey &&
TRUNC( arc[2].y ) < ras.min_ey ) )
{
ras.x = arc[0].x;
ras.y = arc[0].y;
return;
}
dx = PVG_FT_ABS( arc[2].x + arc[0].x - 2 * arc[1].x );
dy = PVG_FT_ABS( arc[2].y + arc[0].y - 2 * arc[1].y );
if ( dx < dy )
dx = dy;
/* We can calculate the number of necessary bisections because */
/* each bisection predictably reduces deviation exactly 4-fold. */
/* Even 32-bit deviation would vanish after 16 bisections. */
draw = 1;
while ( dx > ONE_PIXEL / 4 )
{
dx >>= 2;
draw <<= 1;
}
/* We use decrement counter to count the total number of segments */
/* to draw starting from 2^level. Before each draw we split as */
/* many times as there are trailing zeros in the counter. */
do
{
split = 1;
while ( ( draw & split ) == 0 )
{
gray_split_conic( arc );
arc += 2;
split <<= 1;
}
gray_render_line( RAS_VAR_ arc[0].x, arc[0].y );
arc -= 2;
} while ( --draw );
}
static void
gray_split_cubic( PVG_FT_Vector* base )
{
TPos a, b, c, d;
base[6].x = base[3].x;
c = base[1].x;
d = base[2].x;
base[1].x = a = ( base[0].x + c ) / 2;
base[5].x = b = ( base[3].x + d ) / 2;
c = ( c + d ) / 2;
base[2].x = a = ( a + c ) / 2;
base[4].x = b = ( b + c ) / 2;
base[3].x = ( a + b ) / 2;
base[6].y = base[3].y;
c = base[1].y;
d = base[2].y;
base[1].y = a = ( base[0].y + c ) / 2;
base[5].y = b = ( base[3].y + d ) / 2;
c = ( c + d ) / 2;
base[2].y = a = ( a + c ) / 2;
base[4].y = b = ( b + c ) / 2;
base[3].y = ( a + b ) / 2;
}
static void
gray_render_cubic( RAS_ARG_ const PVG_FT_Vector* control1,
const PVG_FT_Vector* control2,
const PVG_FT_Vector* to )
{
PVG_FT_Vector bez_stack[16 * 3 + 1]; /* enough to accommodate bisections */
PVG_FT_Vector* arc = bez_stack;
TPos dx, dy, dx_, dy_;
TPos dx1, dy1, dx2, dy2;
TPos L, s, s_limit;
arc[0].x = UPSCALE( to->x );
arc[0].y = UPSCALE( to->y );
arc[1].x = UPSCALE( control2->x );
arc[1].y = UPSCALE( control2->y );
arc[2].x = UPSCALE( control1->x );
arc[2].y = UPSCALE( control1->y );
arc[3].x = ras.x;
arc[3].y = ras.y;
/* short-cut the arc that crosses the current band */
if ( ( TRUNC( arc[0].y ) >= ras.max_ey &&
TRUNC( arc[1].y ) >= ras.max_ey &&
TRUNC( arc[2].y ) >= ras.max_ey &&
TRUNC( arc[3].y ) >= ras.max_ey ) ||
( TRUNC( arc[0].y ) < ras.min_ey &&
TRUNC( arc[1].y ) < ras.min_ey &&
TRUNC( arc[2].y ) < ras.min_ey &&
TRUNC( arc[3].y ) < ras.min_ey ) )
{
ras.x = arc[0].x;
ras.y = arc[0].y;
return;
}
for (;;)
{
/* Decide whether to split or draw. See `Rapid Termination */
/* Evaluation for Recursive Subdivision of Bezier Curves' by Thomas */
/* F. Hain, at */
/* http://www.cis.southalabama.edu/~hain/general/Publications/Bezier/Camera-ready%20CISST02%202.pdf */
/* dx and dy are x and y components of the P0-P3 chord vector. */
dx = dx_ = arc[3].x - arc[0].x;
dy = dy_ = arc[3].y - arc[0].y;
L = PVG_FT_HYPOT( dx_, dy_ );
/* Avoid possible arithmetic overflow below by splitting. */
if ( L >= (1 << 23) )
goto Split;
/* Max deviation may be as much as (s/L) * 3/4 (if Hain's v = 1). */
s_limit = L * (TPos)( ONE_PIXEL / 6 );
/* s is L * the perpendicular distance from P1 to the line P0-P3. */
dx1 = arc[1].x - arc[0].x;
dy1 = arc[1].y - arc[0].y;
s = PVG_FT_ABS( dy * dx1 - dx * dy1 );
if ( s > s_limit )
goto Split;
/* s is L * the perpendicular distance from P2 to the line P0-P3. */
dx2 = arc[2].x - arc[0].x;
dy2 = arc[2].y - arc[0].y;
s = PVG_FT_ABS( dy * dx2 - dx * dy2 );
if ( s > s_limit )
goto Split;
/* Split super curvy segments where the off points are so far
from the chord that the angles P0-P1-P3 or P0-P2-P3 become
acute as detected by appropriate dot products. */
if ( dx1 * ( dx1 - dx ) + dy1 * ( dy1 - dy ) > 0 ||
dx2 * ( dx2 - dx ) + dy2 * ( dy2 - dy ) > 0 )
goto Split;
gray_render_line( RAS_VAR_ arc[0].x, arc[0].y );
if ( arc == bez_stack )
return;
arc -= 3;
continue;
Split:
gray_split_cubic( arc );
arc += 3;
}
}
static int
gray_move_to( const PVG_FT_Vector* to,
PWorker worker )
{
TPos x, y;
/* record current cell, if any */
if ( !ras.invalid )
gray_record_cell( worker );
/* start to a new position */
x = UPSCALE( to->x );
y = UPSCALE( to->y );
gray_start_cell( worker, TRUNC( x ), TRUNC( y ) );
ras.x = x;
ras.y = y;
return 0;
}
static void
gray_hline( RAS_ARG_ TCoord x,
TCoord y,
TPos area,
int acount )
{
int coverage;
/* compute the coverage line's coverage, depending on the */
/* outline fill rule */
/* */
/* the coverage percentage is area/(PIXEL_BITS*PIXEL_BITS*2) */
/* */
coverage = (int)( area >> ( PIXEL_BITS * 2 + 1 - 8 ) );
/* use range 0..256 */
if ( coverage < 0 )
coverage = -coverage;
if ( ras.outline.flags & PVG_FT_OUTLINE_EVEN_ODD_FILL )
{
coverage &= 511;
if ( coverage > 256 )
coverage = 512 - coverage;
else if ( coverage == 256 )
coverage = 255;
}
else
{
/* normal non-zero winding rule */
if ( coverage >= 256 )
coverage = 255;
}
y += (TCoord)ras.min_ey;
x += (TCoord)ras.min_ex;
/* PVG_FT_Span.x is an int, so limit our coordinates appropriately */
if ( x >= (1 << 23) )
x = (1 << 23) - 1;
/* PVG_FT_Span.y is an int, so limit our coordinates appropriately */
if ( y >= (1 << 23) )
y = (1 << 23) - 1;
if ( coverage )
{
PVG_FT_Span* span;
int count;
int skip;
/* see whether we can add this span to the current list */
count = ras.num_gray_spans;
span = ras.gray_spans + count - 1;
if ( count > 0 &&
span->y == y &&
span->x + span->len == x &&
span->coverage == coverage )
{
span->len = span->len + acount;
return;
}
if ( count >= PVG_FT_MAX_GRAY_SPANS )
{
if ( ras.render_span && count > ras.skip_spans )
{
skip = ras.skip_spans > 0 ? ras.skip_spans : 0;
ras.render_span( ras.num_gray_spans - skip,
ras.gray_spans + skip,
ras.render_span_data );
}
ras.skip_spans -= ras.num_gray_spans;
/* ras.render_span( span->y, ras.gray_spans, count ); */
ras.num_gray_spans = 0;
span = ras.gray_spans;
}
else
span++;
/* add a gray span to the current list */
span->x = x;
span->len = acount;
span->y = y;
span->coverage = (unsigned char)coverage;
ras.num_gray_spans++;
}
}
static void
gray_sweep( RAS_ARG)
{
int yindex;
if ( ras.num_cells == 0 )
return;
for ( yindex = 0; yindex < ras.ycount; yindex++ )
{
PCell cell = ras.ycells[yindex];
TCoord cover = 0;
TCoord x = 0;
for ( ; cell != NULL; cell = cell->next )
{
TArea area;
if ( cell->x > x && cover != 0 )
gray_hline( RAS_VAR_ x, yindex, cover * ( ONE_PIXEL * 2 ),
cell->x - x );
cover += cell->cover;
area = cover * ( ONE_PIXEL * 2 ) - cell->area;
if ( area != 0 && cell->x >= 0 )
gray_hline( RAS_VAR_ cell->x, yindex, area, 1 );
x = cell->x + 1;
}
if ( ras.count_ex > x && cover != 0 )
gray_hline( RAS_VAR_ x, yindex, cover * ( ONE_PIXEL * 2 ),
ras.count_ex - x );
}
}
/*************************************************************************/
/* */
/* The following function should only compile in stand_alone mode, */
/* i.e., when building this component without the rest of FreeType. */
/* */
/*************************************************************************/
/*************************************************************************/
/* */
/* <Function> */
/* PVG_FT_Outline_Decompose */
/* */
/* <Description> */
/* Walks over an outline's structure to decompose it into individual */
/* segments and Bezier arcs. This function is also able to emit */
/* `move to' and `close to' operations to indicate the start and end */
/* of new contours in the outline. */
/* */
/* <Input> */
/* outline :: A pointer to the source target. */
/* */
/* user :: A typeless pointer which is passed to each */
/* emitter during the decomposition. It can be */
/* used to store the state during the */
/* decomposition. */
/* */
/* <Return> */
/* Error code. 0 means success. */
/* */
static
int PVG_FT_Outline_Decompose( const PVG_FT_Outline* outline,
void* user )
{
#undef SCALED
#define SCALED( x ) (x)
PVG_FT_Vector v_last;
PVG_FT_Vector v_control;
PVG_FT_Vector v_start;
PVG_FT_Vector* point;
PVG_FT_Vector* limit;
char* tags;
int n; /* index of contour in outline */
int first; /* index of first point in contour */
int error;
char tag; /* current point's state */
if ( !outline )
return ErrRaster_Invalid_Outline;
first = 0;
for ( n = 0; n < outline->n_contours; n++ )
{
int last; /* index of last point in contour */
last = outline->contours[n];
if ( last < 0 )
goto Invalid_Outline;
limit = outline->points + last;
v_start = outline->points[first];
v_start.x = SCALED( v_start.x );
v_start.y = SCALED( v_start.y );
v_last = outline->points[last];
v_last.x = SCALED( v_last.x );
v_last.y = SCALED( v_last.y );
v_control = v_start;
point = outline->points + first;
tags = outline->tags + first;
tag = PVG_FT_CURVE_TAG( tags[0] );
/* A contour cannot start with a cubic control point! */
if ( tag == PVG_FT_CURVE_TAG_CUBIC )
goto Invalid_Outline;
/* check first point to determine origin */
if ( tag == PVG_FT_CURVE_TAG_CONIC )
{
/* first point is conic control. Yes, this happens. */
if ( PVG_FT_CURVE_TAG( outline->tags[last] ) == PVG_FT_CURVE_TAG_ON )
{
/* start at last point if it is on the curve */
v_start = v_last;
limit--;
}
else
{
/* if both first and last points are conic, */
/* start at their middle and record its position */
/* for closure */
v_start.x = ( v_start.x + v_last.x ) / 2;
v_start.y = ( v_start.y + v_last.y ) / 2;
v_last = v_start;
}
point--;
tags--;
}
error = gray_move_to( &v_start, user );
if ( error )
goto Exit;
while ( point < limit )
{
point++;
tags++;
tag = PVG_FT_CURVE_TAG( tags[0] );
switch ( tag )
{
case PVG_FT_CURVE_TAG_ON: /* emit a single line_to */
{
PVG_FT_Vector vec;
vec.x = SCALED( point->x );
vec.y = SCALED( point->y );
gray_render_line(user, UPSCALE(vec.x), UPSCALE(vec.y));
continue;
}
case PVG_FT_CURVE_TAG_CONIC: /* consume conic arcs */
{
v_control.x = SCALED( point->x );
v_control.y = SCALED( point->y );
Do_Conic:
if ( point < limit )
{
PVG_FT_Vector vec;
PVG_FT_Vector v_middle;
point++;
tags++;
tag = PVG_FT_CURVE_TAG( tags[0] );
vec.x = SCALED( point->x );
vec.y = SCALED( point->y );
if ( tag == PVG_FT_CURVE_TAG_ON )
{
gray_render_conic(user, &v_control, &vec);
continue;
}
if ( tag != PVG_FT_CURVE_TAG_CONIC )
goto Invalid_Outline;
v_middle.x = ( v_control.x + vec.x ) / 2;
v_middle.y = ( v_control.y + vec.y ) / 2;
gray_render_conic(user, &v_control, &v_middle);
v_control = vec;
goto Do_Conic;
}
gray_render_conic(user, &v_control, &v_start);
goto Close;
}
default: /* PVG_FT_CURVE_TAG_CUBIC */
{
PVG_FT_Vector vec1, vec2;
if ( point + 1 > limit ||
PVG_FT_CURVE_TAG( tags[1] ) != PVG_FT_CURVE_TAG_CUBIC )
goto Invalid_Outline;
point += 2;
tags += 2;
vec1.x = SCALED( point[-2].x );
vec1.y = SCALED( point[-2].y );
vec2.x = SCALED( point[-1].x );
vec2.y = SCALED( point[-1].y );
if ( point <= limit )
{
PVG_FT_Vector vec;
vec.x = SCALED( point->x );
vec.y = SCALED( point->y );
gray_render_cubic(user, &vec1, &vec2, &vec);
continue;
}
gray_render_cubic(user, &vec1, &vec2, &v_start);
goto Close;
}
}
}
/* close the contour with a line segment */
gray_render_line(user, UPSCALE(v_start.x), UPSCALE(v_start.y));
Close:
first = last + 1;
}
return 0;
Exit:
return error;
Invalid_Outline:
return ErrRaster_Invalid_Outline;
}
typedef struct TBand_
{
TPos min, max;
} TBand;
static int
gray_convert_glyph_inner( RAS_ARG )
{
volatile int error = 0;
if ( pvg_ft_setjmp( ras.jump_buffer ) == 0 )
{
error = PVG_FT_Outline_Decompose( &ras.outline, &ras );
if ( !ras.invalid )
gray_record_cell( RAS_VAR );
}
else
{
error = ErrRaster_Memory_Overflow;
}
return error;
}
static int
gray_convert_glyph( RAS_ARG )
{
TBand bands[40];
TBand* volatile band;
int volatile n, num_bands;
TPos volatile min, max, max_y;
PVG_FT_BBox* clip;
int skip;
ras.num_gray_spans = 0;
/* Set up state in the raster object */
gray_compute_cbox( RAS_VAR );
/* clip to target bitmap, exit if nothing to do */
clip = &ras.clip_box;
if ( ras.max_ex <= clip->xMin || ras.min_ex >= clip->xMax ||
ras.max_ey <= clip->yMin || ras.min_ey >= clip->yMax )
return 0;
if ( ras.min_ex < clip->xMin ) ras.min_ex = clip->xMin;
if ( ras.min_ey < clip->yMin ) ras.min_ey = clip->yMin;
if ( ras.max_ex > clip->xMax ) ras.max_ex = clip->xMax;
if ( ras.max_ey > clip->yMax ) ras.max_ey = clip->yMax;
ras.count_ex = ras.max_ex - ras.min_ex;
ras.count_ey = ras.max_ey - ras.min_ey;
/* set up vertical bands */
num_bands = (int)( ( ras.max_ey - ras.min_ey ) / ras.band_size );
if ( num_bands == 0 )
num_bands = 1;
if ( num_bands >= 39 )
num_bands = 39;
ras.band_shoot = 0;
min = ras.min_ey;
max_y = ras.max_ey;
for ( n = 0; n < num_bands; n++, min = max )
{
max = min + ras.band_size;
if ( n == num_bands - 1 || max > max_y )
max = max_y;
bands[0].min = min;
bands[0].max = max;
band = bands;
while ( band >= bands )
{
TPos bottom, top, middle;
int error;
{
PCell cells_max;
int yindex;
int cell_start, cell_end, cell_mod;
ras.ycells = (PCell*)ras.buffer;
ras.ycount = band->max - band->min;
cell_start = sizeof ( PCell ) * ras.ycount;
cell_mod = cell_start % sizeof ( TCell );
if ( cell_mod > 0 )
cell_start += sizeof ( TCell ) - cell_mod;
cell_end = ras.buffer_size;
cell_end -= cell_end % sizeof( TCell );
cells_max = (PCell)( (char*)ras.buffer + cell_end );
ras.cells = (PCell)( (char*)ras.buffer + cell_start );
if ( ras.cells >= cells_max )
goto ReduceBands;
ras.max_cells = (int)(cells_max - ras.cells);
if ( ras.max_cells < 2 )
goto ReduceBands;
for ( yindex = 0; yindex < ras.ycount; yindex++ )
ras.ycells[yindex] = NULL;
}
ras.num_cells = 0;
ras.invalid = 1;
ras.min_ey = band->min;
ras.max_ey = band->max;
ras.count_ey = band->max - band->min;
error = gray_convert_glyph_inner( RAS_VAR );
if ( !error )
{
gray_sweep( RAS_VAR);
band--;
continue;
}
else if ( error != ErrRaster_Memory_Overflow )
return 1;
ReduceBands:
/* render pool overflow; we will reduce the render band by half */
bottom = band->min;
top = band->max;
middle = bottom + ( ( top - bottom ) >> 1 );
/* This is too complex for a single scanline; there must */
/* be some problems. */
if ( middle == bottom )
{
return ErrRaster_OutOfMemory;
}
if ( bottom-top >= ras.band_size )
ras.band_shoot++;
band[1].min = bottom;
band[1].max = middle;
band[0].min = middle;
band[0].max = top;
band++;
}
}
if ( ras.render_span && ras.num_gray_spans > ras.skip_spans )
{
skip = ras.skip_spans > 0 ? ras.skip_spans : 0;
ras.render_span( ras.num_gray_spans - skip,
ras.gray_spans + skip,
ras.render_span_data );
}
ras.skip_spans -= ras.num_gray_spans;
if ( ras.band_shoot > 8 && ras.band_size > 16 )
ras.band_size = ras.band_size / 2;
return 0;
}
static int
gray_raster_render( RAS_ARG_ void* buffer, long buffer_size,
const PVG_FT_Raster_Params* params )
{
const PVG_FT_Outline* outline = (const PVG_FT_Outline*)params->source;
if ( outline == NULL )
return ErrRaster_Invalid_Outline;
/* return immediately if the outline is empty */
if ( outline->n_points == 0 || outline->n_contours <= 0 )
return 0;
if ( !outline->contours || !outline->points )
return ErrRaster_Invalid_Outline;
if ( outline->n_points !=
outline->contours[outline->n_contours - 1] + 1 )
return ErrRaster_Invalid_Outline;
/* this version does not support monochrome rendering */
if ( !( params->flags & PVG_FT_RASTER_FLAG_AA ) )
return ErrRaster_Invalid_Mode;
if ( !( params->flags & PVG_FT_RASTER_FLAG_DIRECT ) )
return ErrRaster_Invalid_Mode;
/* compute clipping box */
if ( params->flags & PVG_FT_RASTER_FLAG_CLIP )
{
ras.clip_box = params->clip_box;
}
else
{
ras.clip_box.xMin = -(1 << 23);
ras.clip_box.yMin = -(1 << 23);
ras.clip_box.xMax = (1 << 23) - 1;
ras.clip_box.yMax = (1 << 23) - 1;
}
gray_init_cells( RAS_VAR_ buffer, buffer_size );
ras.outline = *outline;
ras.num_cells = 0;
ras.invalid = 1;
ras.band_size = (int)(buffer_size / (long)(sizeof(TCell) * 8));
ras.render_span = (PVG_FT_Raster_Span_Func)params->gray_spans;
ras.render_span_data = params->user;
return gray_convert_glyph( RAS_VAR );
}
void
PVG_FT_Raster_Render(const PVG_FT_Raster_Params *params)
{
char stack[PVG_FT_MINIMUM_POOL_SIZE];
size_t length = PVG_FT_MINIMUM_POOL_SIZE;
TWorker worker;
worker.skip_spans = 0;
int rendered_spans = 0;
int error = gray_raster_render(&worker, stack, length, params);
while(error == ErrRaster_OutOfMemory) {
if(worker.skip_spans < 0)
rendered_spans += -worker.skip_spans;
worker.skip_spans = rendered_spans;
length *= 2;
void* heap = malloc(length);
error = gray_raster_render(&worker, heap, length, params);
free(heap);
}
}
/* END */