ref: 13b1ea74932158069ab1f4c584db81477d9f3551
dir: /sys/src/libmemdraw/arc.c/
#include <u.h> #include <libc.h> #include <draw.h> #include <memdraw.h> #include <memlayer.h> /* * elarc(dst,c,a,b,t,src,sp,alpha,phi) * draws the part of an ellipse between rays at angles alpha and alpha+phi * measured counterclockwise from the positive x axis. other * arguments are as for ellipse(dst,c,a,b,t,src,sp) */ enum { R, T, L, B /* right, top, left, bottom */ }; static Point corners[] = { {1,1}, {-1,1}, {-1,-1}, {1,-1} }; /* * make a "wedge" mask covering the desired angle and contained in * a surrounding square; draw a full ellipse; intersect that with the * wedge to make a mask through which to copy src to dst. */ void memarc(Memimage *dst, Point c, int a, int b, int t, Memimage *src, Point sp, int alpha, int phi, int op) { int i, w, beta, tmp, c1, c2, m, m1; Rectangle rect; Point p, bnd[8]; Memimage *wedge, *figure, *mask; if(phi == 0) return; if(phi <= -360 || phi >= 360){ memellipse(dst, c, a, b, t, src, sp, op); return; } alpha %= 360; alpha = -alpha; /* compensate for upside-down coords */ phi = -phi; beta = alpha + phi; if(phi < 0){ tmp = alpha; alpha = beta; beta = tmp; phi = -phi; } while(alpha < 0) alpha += 360; while(beta < 0) beta += 360; c1 = alpha/90 & 3; /* number of nearest corner */ c2 = beta/90 & 3; /* * icossin returns point at radius ICOSSCALE. * multiplying by m1 moves it outside the ellipse */ if(a < 0) a = -a; if(b < 0) b = -b; w = t; if(w < 0) w = 0; rect = Rect(-a-w, -b-w, a+w+1, b+w+1); m = rect.max.x; /* inradius of bounding square */ if(m < rect.max.y) m = rect.max.y; m1 = (m+ICOSSCALE-1) >> 10; m = m1 << 10; /* assure m1*cossin is inside */ i = 0; bnd[i++] = Pt(0,0); icossin(alpha, &p.x, &p.y); bnd[i++] = mulpt(p, m1); for(;;) { bnd[i++] = mulpt(corners[c1], m); if(c1==c2 && phi<180) break; c1 = (c1+1) & 3; phi -= 90; } icossin(beta, &p.x, &p.y); bnd[i++] = mulpt(p, m1); figure = nil; mask = nil; wedge = allocmemimage(rect, GREY1); if(wedge == nil) goto Return; memfillcolor(wedge, DTransparent); memfillpoly(wedge, bnd, i, ~0, memopaque, ZP, S); figure = allocmemimage(rect, GREY1); if(figure == nil) goto Return; memfillcolor(figure, DTransparent); memellipse(figure, ZP, a, b, t, memopaque, ZP, S); mask = allocmemimage(rect, GREY1); if(mask == nil) goto Return; memfillcolor(mask, DTransparent); memimagedraw(mask, rect, figure, rect.min, wedge, rect.min, S); c = subpt(c, dst->r.min); memdraw(dst, dst->r, src, subpt(sp, c), mask, subpt(ZP, c), op); Return: freememimage(wedge); freememimage(figure); freememimage(mask); }