Core Graphics Learning Note Image Drawing (ii)

1. Three ways to draw arrows

  Drawing code//cgcontextref con = uigraphicsgetcurrentcontext ();////draw a black (by default) vertical line,the Shaft of the arrow shaft//Cgcontextmovetopoint (con, +);//Cgcontextaddlinetopoint (con, +);//Cgconte Xtsetlinewidth (con);//Cgcontextstrokepath (con);////draw a red triangle,the point of the arrow//Cgcontextse Tfillcolorwithcolor (Con, [[Uicolor Redcolor] cgcolor]);//Cgcontextmovetopoint (con, +);//Cgcontextaddlinetopoi NT (con, 0);//Cgcontextaddlinetopoint (con, +);//Cgcontextfillpath (con);////snip a triangle out of th     e shaft by drawing in clear blend mode//cgcontextmovetopoint (Con, n, d);//Cgcontextmovetopoint (Con, 100, 90);// Cgcontextmovetopoint (Con, max),//Cgcontextsetblendmode (con, kcgblendmodeclear);//Cgcontextsetalpha (Con, 1     .0);//Cgcontextfillpath (con); When you need to obtain Cgpath, you can use uibezierpath//uibezierpath *p = [Uibezierpath bezierpath];////[P moveToPoint:Cgpointmake (+)];//[P addlinetopoint:cgpointmake (+)];//[P setlinewidth:20];//[P stroke];//[UI Color Redcolor] set];//[P removeallpoints];//[P Movetopoint:cgpointmake (+)];//[P ADDLINETOPOINT:CGPOINTMA Ke (0)];//[P addlinetopoint:cgpointmake (+)];//[P fill];////[P removeallpoints];//[P Movetopo    Int:cgpointmake (101)];//[P addlinetopoint:cgpointmake (+)];//[P Addlinetopoint:cgpointmake (110, 101)];//       [P fillwithblendmode:kcgblendmodeclear alpha:1.0];    Clipping cgcontextref con = uigraphicsgetcurrentcontext ();    Punch triangular hole in the context clipping region cgcontextmovetopoint (Con, 90, 100);    Cgcontextaddlinetopoint (Con, 100, 90);    Cgcontextaddlinetopoint (Con, 110, 100);    Cgcontextclosepath (con);    Cgcontextaddrect (Con, cgcontextgetclipboundingbox (con));    Cgcontexteoclip (con);    Draw the vertical line cgcontextmovetopoint (con, 100, 100); Cgcontextaddlinetopoint (CON, 100, 19);    Cgcontextsetlinewidth (Con, 20);    Cgcontextstrokepath (con);    Draw the red triangle.the point of the arrow cgcontextsetfillcolorwithcolor (Con, [[Uicolor Redcolor] cgcolor]);    Cgcontextmovetopoint (Con, 80, 25);    Cgcontextaddlinetopoint (Con, 100, 0);    Cgcontextaddlinetopoint (Con, 120, 25); Cgcontextfillpath (con);

Effect:

    Cgcontextref con = Uigraphicsgetcurrentcontext ();    [Self arrowimage] drawatpoint:cgpointmake (0, 0)];        for (int i=0; i<3; i++) {CGCONTEXTTRANSLATECTM (con, 20, 100);        Cgcontextrotatectm (Con, 30*m_pi/180);        Cgcontexttranslatectm (Con,-20,-100);            [Self arrowimage] drawatpoint:cgpointmake (0, 0)];    }//}-(UIImage *) arrowimage{uigraphicsbeginimagecontextwithoptions (Cgsizemake (+), NO, 0.0);    Cgcontextref con = Uigraphicsgetcurrentcontext ();    Punch triangular hole in the context clipping region cgcontextmovetopoint (Con, 10, 100);    Cgcontextaddlinetopoint (Con, 20, 90);    Cgcontextaddlinetopoint (Con, 30, 100);    Cgcontextclosepath (con);    Cgcontextaddrect (Con, cgcontextgetclipboundingbox (con));    Cgcontexteoclip (con);    Draw the vertical line cgcontextmovetopoint (con, 20, 100);    Cgcontextaddlinetopoint (Con, 20, 19);    Cgcontextsetlinewidth (Con, 20);    Cgcontextstrokepath (con); Draw the red triangle.the point ofThe arrow cgcontextsetfillcolorwithcolor (Con, [[Uicolor Redcolor] cgcolor]);    Cgcontextmovetopoint (Con, 0, 25);    Cgcontextaddlinetopoint (Con, 20, 0);    Cgcontextaddlinetopoint (Con, 40, 25);        Cgcontextfillpath (con);    UIImage *im = Uigraphicsgetimagefromcurrentimagecontext ();    Uigraphicsendimagecontext (); return im;}

When I'm not drawing in (0,0) There's a problem, as if it was caused by a coordinate system change.

    Cgcontextref con = Uigraphicsgetcurrentcontext ();    [Self arrowimage]  drawatpoint:cgpointmake ();    for (int i=0; i<12; i++) {        cgcontexttranslatectm (con, +);        Cgcontextrotatectm (Con, 30*m_pi/180);        Cgcontexttranslatectm (Con, -20, -100);        [Self arrowimage] drawatpoint:cgpointmake ();            }

Have not found the reason, have to know the children's shoes, welcome to inform, communicate together

Core Graphics Learning Note Image Drawing (ii)