[dense] Add code for curve flattening at load time
src/base/ftobjs.c: Add Lerp, conic_to2, ft_decompose_outline functions
This commit is contained in:
Anurag Thakur
parent
b2f570a2bb
commit
2254ce1906
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@ -42,6 +42,7 @@
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#include <freetype/internal/services/svkern.h>
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#include <freetype/internal/services/svtteng.h>
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#include <math.h>
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#include <freetype/ftdriver.h>
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#ifdef FT_CONFIG_OPTION_MAC_FONTS
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@ -2548,6 +2549,306 @@
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}
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static FT_Vector
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Lerp( float T, FT_Vector P0, FT_Vector P1 )
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{
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FT_Vector p;
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p.x = P0.x + T * ( P1.x - P0.x );
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p.y = P0.y + T * ( P1.y - P0.y );
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return p;
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}
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int conic_to2(FT_GlyphSlot* slot, FT_Vector *control, FT_Vector *from, FT_Vector *to, FT_PreLine *ptr)
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{
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/*
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Calculate devsq as the square of four times the
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distance from the control point to the midpoint of the curve.
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This is the place at which the curve is furthest from the
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line joining the control points.
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4 x point on curve = p0 + 2p1 + p2
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4 x midpoint = 4p1
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The division by four is omitted to save time.
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*/
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FT_Vector aP0 = { from->x , from->y};
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FT_Vector aP1 = { control->x, control->y };
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FT_Vector aP2 = { to->x, to->y };
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float devx = aP0.x - aP1.x - aP1.x + aP2.x;
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float devy = aP0.y - aP1.y - aP1.y + aP2.y;
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float devsq = devx * devx + devy * devy;
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if ( devsq < 0.333f )
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{
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FT_PreLine pl3 = malloc(sizeof(FT_PreLineRec));
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pl3->x1 = (*ptr)->x2;
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pl3->y1 = (*ptr)->y2;
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pl3->x2 = aP2.x;
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pl3->y2 = aP2.y;
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pl3->next = NULL;
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(*ptr)->next = pl3;
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*ptr = (*ptr)->next;
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return 0;
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}
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/*
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According to Raph Levien, the reason for the subdivision by n (instead of
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recursive division by the Casteljau system) is that "I expect the flatness
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computation to be semi-expensive (it's done once rather than on each potential
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subdivision) and also because you'll often get fewer subdivisions. Taking a
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circular arc as a simplifying assumption, where I get n, a recursive approach
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would get 2^ceil(lg n), which, if I haven't made any horrible mistakes, is
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expected to be 33% more in the limit".
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*/
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const float tol = 3.0f;
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int n = (int)floor( sqrt( sqrt( tol * devsq ) ) )/8;
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FT_Vector p = aP0;
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float nrecip = 1.0f / ( n + 1.0f );
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float t = 0.0f;
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for ( int i = 0; i < n; i++ )
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{
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t += nrecip;
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FT_Vector next = Lerp( t, Lerp( t, aP0, aP1 ), Lerp( t, aP1, aP2 ) );
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FT_PreLine pl4 = malloc(sizeof(FT_PreLineRec));
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pl4->x1 = (*ptr)->x2;
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pl4->y1 = (*ptr)->y2;
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pl4->x2 = next.x;
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pl4->y2 = next.y;
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pl4->next = NULL;
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(*ptr)->next = pl4;
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*ptr = (*ptr)->next;
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p = next;
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}
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FT_PreLine pl5 = malloc(sizeof(FT_PreLineRec));
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pl5->x1 = (*ptr)->x2;
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pl5->y1 = (*ptr)->y2;
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pl5->x2 = aP2.x;
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pl5->y2 = aP2.y;
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pl5->next = NULL;
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(*ptr)->next = pl5;
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*ptr = (*ptr)->next;
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return 0;
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}
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/**
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* Convert the outline data of slot to prelines
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*/
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FT_Error ft_decompose_outline(FT_GlyphSlot* slot){
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FT_Vector v_last;
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FT_Vector v_control;
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FT_Vector v_start;
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FT_Vector* point;
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FT_Vector* limit;
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char* tags;
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FT_Error error;
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FT_Int n; /* index of contour in outline */
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FT_Int first; /* index of first point in contour */
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FT_Int last; /* index of last point in contour */
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FT_Int tag; /* current point's state */
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FT_Int shift;
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FT_Pos delta;
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FT_Outline* outline = &(*slot)->outline;
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if ( !outline )
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return FT_THROW( Invalid_Outline );
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last = -1;
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FT_PreLine ptr = (*slot)->prelines;
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for ( n = 0; n < outline->n_contours; n++ )
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{
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FT_TRACE5(( "ft_decompose_outline: Contour %d\n", n ));
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first = last + 1;
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last = outline->contours[n];
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if ( last < first ){
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FT_TRACE5(( "Invalid Outline"));
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break;
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}
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limit = outline->points + last;
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v_start = outline->points[first];
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v_last = outline->points[last];
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v_control = v_start;
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point = outline->points + first;
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tags = outline->tags + first;
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tag = FT_CURVE_TAG( tags[0] );
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/* A contour cannot start with a cubic control point! */
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if ( tag == FT_CURVE_TAG_CUBIC )
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{
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FT_TRACE5(( "Invalid Outline"));
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break;
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}
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/* check first point to determine origin */
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if ( tag == FT_CURVE_TAG_CONIC )
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{
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/* first point is conic control. Yes, this happens. */
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if ( FT_CURVE_TAG( outline->tags[last] ) == FT_CURVE_TAG_ON )
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{
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/* start at last point if it is on the curve */
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v_start = v_last;
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limit--;
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}
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else
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{
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/* if both first and last points are conic, */
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/* start at their middle and record its position */
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/* for closure */
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v_start.x = ( v_start.x + v_last.x ) / 2;
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v_start.y = ( v_start.y + v_last.y ) / 2;
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/* v_last = v_start; */
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}
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point--;
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tags--;
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}
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FT_TRACE5(( " move to (%.2f, %.2f)\n",
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(double)v_start.x / 64, (double)v_start.y / 64 ));
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FT_PreLine pl = malloc(sizeof(FT_PreLineRec));
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pl->x1 = v_start.x;
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pl->y1 = v_start.y;
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pl->x2 = v_start.x;
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pl->y2 = v_start.y;
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pl->next = NULL;
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if ( ( *slot )->prelines == NULL )
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{
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ptr = ( *slot )->prelines = pl;
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}
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else
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{
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ptr->next = pl;
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ptr = ptr->next;
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}
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while ( point < limit )
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{
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point++;
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tags++;
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tag = FT_CURVE_TAG( tags[0] );
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switch ( tag )
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{
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case FT_CURVE_TAG_ON: /* emit a single line_to */
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{
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FT_Vector vec;
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vec.x = point->x;
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vec.y = point->y;
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FT_TRACE5(( " line to (%.2f, %.2f)\n",
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(double)vec.x / 64, (double)vec.y / 64 ));
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FT_PreLine pl3 = malloc(sizeof(FT_PreLineRec));
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pl3->x1 = ptr->x2;
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pl3->y1 = ptr->y2;
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pl3->x2 = vec.x;
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pl3->y2 = vec.y;
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pl3->next = NULL;
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ptr->next = pl3;
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ptr = ptr->next;
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continue;
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}
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case FT_CURVE_TAG_CONIC: /* consume conic arcs */
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v_control.x = point->x ;
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v_control.y = point->y ;
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Do_Conic:
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if ( point < limit )
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{
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FT_Vector vec;
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FT_Vector v_middle;
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point++;
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tags++;
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tag = FT_CURVE_TAG( tags[0] );
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vec.x = point->x;
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vec.y = point->y;
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if ( tag == FT_CURVE_TAG_ON )
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{
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FT_TRACE5(( " conic to (%.2f, %.2f)"
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" with control (%.2f, %.2f)\n",
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(double)vec.x / 64,
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(double)vec.y / 64,
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(double)v_control.x / 64,
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(double)v_control.y / 64 ));
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FT_Vector vex0 = {ptr->x2, ptr->y2};
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error = conic_to2(slot, &v_control, &vex0,&vec , &ptr);
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continue;
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}
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if ( tag != FT_CURVE_TAG_CONIC )
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{
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FT_TRACE5( ( "Invalid Outline" ) );
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break;
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}
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v_middle.x = ( v_control.x + vec.x ) / 2;
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v_middle.y = ( v_control.y + vec.y ) / 2;
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FT_TRACE5(( " conic to (%.2f, %.2f)"
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" with control (%.2f, %.2f)\n",
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(double)v_middle.x / 64,
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(double)v_middle.y / 64,
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(double)v_control.x / 64,
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(double)v_control.y / 64 ));
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FT_Vector vex = {ptr->x2, ptr->y2};
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error = conic_to2(slot, &v_control, &vex,&v_middle, &ptr);
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v_control = vec;
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goto Do_Conic;
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}
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FT_TRACE5(( " conic to (%.2f, %.2f)"
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" with control (%.2f, %.2f)\n",
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(double)v_start.x / 64,
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(double)v_start.y / 64,
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(double)v_control.x / 64,
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(double)v_control.y / 64 ));
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FT_Vector vex2 = {ptr->x2, ptr->y2};
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error = conic_to2( slot, &v_control, &vex2, &v_start, &ptr );
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}
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}
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/* close the contour with a line segment */
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FT_TRACE5(( " line to (%.2f, %.2f)\n",
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(double)v_start.x / 64, (double)v_start.y / 64 ));
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FT_PreLine pl2 = malloc(sizeof(FT_PreLineRec));
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pl2->x1 = ptr->x2;
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pl2->y1 = ptr->y2;
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pl2->x2 = v_start.x;
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pl2->y2 = v_start.y;
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pl2->next = NULL;
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ptr->next = pl2;
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ptr = ptr->next;
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}
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return 0;
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}
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static FT_Error
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ft_open_face_internal( FT_Library library,
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const FT_Open_Args* args,
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