今天主要講解圖層的lineJoin miterLimit 屬性。

lineJoin 連接點(diǎn)類型，對(duì)應(yīng)曲線節(jié)點(diǎn)的顯示樣式。可能會(huì)受到miterLimit影響。看四個(gè)例子

kCALineJoinMiter樣式

    CAShapeLayer * Star = [CAShapeLayer layer];
    Star.frame       = CGRectMake(102, 254.56, 183.74, 193.44);
    Star.lineCap     = kCALineCapRound;
    Star.lineJoin    = kCALineJoinMiter;
    Star.miterLimit  = 4;
    Star.fillColor   = [UIColor colorWithRed:0.847 green: 0.847 blue:0.847 alpha:1].CGColor;
    Star.strokeColor = [UIColor colorWithRed:0.592 green: 0.592 blue:0.592 alpha:1].CGColor;
    Star.lineWidth   = 15;

kCALineJoinRound樣式

    CAShapeLayer * Star = [CAShapeLayer layer];
    Star.frame       = CGRectMake(102, 254.56, 183.74, 193.44);
    Star.lineCap     = kCALineCapRound;
    Star.lineJoin    = kCALineJoinRound;
    Star.fillColor   = [UIColor colorWithRed:0.847 green: 0.847 blue:0.847 alpha:1].CGColor;
    Star.strokeColor = [UIColor colorWithRed:0.592 green: 0.592 blue:0.592 alpha:1].CGColor;
    Star.lineWidth   = 15;
    Star.path        = [self StarPath].CGPath;

kCALineJoinBevel樣式

    CAShapeLayer * Star = [CAShapeLayer layer];
    Star.frame       = CGRectMake(102, 254.56, 183.74, 193.44);
    Star.lineCap     = kCALineCapRound;
    Star.lineJoin    = kCALineJoinBevel;
    Star.fillColor   = [UIColor colorWithRed:0.847 green: 0.847 blue:0.847 alpha:1].CGColor;
    Star.strokeColor = [UIColor colorWithRed:0.592 green: 0.592 blue:0.592 alpha:1].CGColor;
    Star.lineWidth   = 15;
    Star.path        = [self StarPath].CGPath;

miterLimit 影響lineJoin樣式

    CAShapeLayer * Star = [CAShapeLayer layer];
    Star.frame       = CGRectMake(102, 254.56, 183.74, 193.44);
    Star.lineCap     = kCALineCapRound;
    Star.lineJoin    = kCALineJoinMiter;
    Star.miterLimit  = 1;
    Star.fillColor   = [UIColor colorWithRed:0.847 green: 0.847 blue:0.847 alpha:1].CGColor;
    Star.strokeColor = [UIColor colorWithRed:0.592 green: 0.592 blue:0.592 alpha:1].CGColor;
    Star.lineWidth   = 15;
    Star.path        = [self StarPath].CGPath;

總結(jié)：miterLimit是最大斜接長(zhǎng)度，只有l(wèi)ineJoin屬性為kCALineJoinMiter時(shí)miterLimit才有效，當(dāng)銜接角度太小時(shí)，斜接長(zhǎng)度就會(huì)很大，如果設(shè)置了 miterLimit并且當(dāng)斜接長(zhǎng)度大于這個(gè)值時(shí)，便會(huì)對(duì)應(yīng)裁切掉多余區(qū)域。就像上面第四種情況。