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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
Core Graphics 学习笔记 之 Image Drawing(二)
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