Core Graphics 学习笔记 之 Image Drawing(二)

1.绘制箭头的三种方式

  // Drawing code//    CGContextRef con = UIGraphicsGetCurrentContext();//    //draw a black(by default) vertical line,the shaft of the arrow  箭杆//    CGContextMoveToPoint(con, 100, 100);//    CGContextAddLineToPoint(con, 100, 19);//    CGContextSetLineWidth(con, 20);//    CGContextStrokePath(con);//    //draw a 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);//    //snip a triangle out of the shaft by drawing in clear blend mode//    CGContextMoveToPoint(con, 90, 100);//    CGContextMoveToPoint(con, 100, 90);//    CGContextMoveToPoint(con, 110, 100);//    CGContextSetBlendMode(con, kCGBlendModeClear);//    CGContextSetAlpha(con, 1.0);//    CGContextFillPath(con);     //当需要获取CGPath时，可以使用UIBezierPath//    UIBezierPath *p = [UIBezierPath bezierPath];//    //    [p moveToPoint:CGPointMake(100, 100)];//    [p addLineToPoint:CGPointMake(100, 19)];//    [p setLineWidth:20];//    [p stroke];//    [[UIColor redColor] set];//    [p removeAllPoints];//    [p moveToPoint:CGPointMake(80, 25)];//    [p addLineToPoint:CGPointMake(100, 0)];//    [p addLineToPoint:CGPointMake(120, 25)];//    [p fill];//    //    [p removeAllPoints];//    [p moveToPoint:CGPointMake(90, 101)];//    [p addLineToPoint:CGPointMake(100, 90)];//    [p addLineToPoint:CGPointMake(110, 101)];//    [p fillWithBlendMode:kCGBlendModeClear alpha:1.0];       //Clipping    CGContextRef con = UIGraphicsGetCurrentContext();    //punch triangular hole in 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);

效果：

    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(40, 100), NO, 0.0);    CGContextRef con = UIGraphicsGetCurrentContext();    //punch triangular hole in 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 of the 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;}

当我不是绘制在（0，0）时就有问题，好像是由坐标系统改变导致的

    CGContextRef con = UIGraphicsGetCurrentContext();    [[self arrowImage]  drawAtPoint:CGPointMake(150, 200)];    for (int i=0; i<12; i++) {        CGContextTranslateCTM(con, 20, 100);        CGContextRotateCTM(con, 30*M_PI/180);        CGContextTranslateCTM(con, -20, -100);        [[self arrowImage] drawAtPoint:CGPointMake(150, 200)];            }

尚未找到原因，有知道的童鞋，欢迎告知，一起交流