Ios 在CGContext上翻转旋转的文本

图片：

我想得到90-270度的文本（文本“Aroma 7”到“Aroma 17”），旋转180度

我的代码：

 for (int i=0; i<24; i++) {
    CGContextSaveGState(context);
    CGContextRef context = UIGraphicsGetCurrentContext();
    NSString *str = [NSString stringWithFormat:@"Aroma %d", i];

    CGContextTranslateCTM(context, radius, radius);
    CGContextRotateCTM(context, i * 15 * M_PI/180.0);
    [[UIColor whiteColor] set];

    CGContextTranslateCTM(context, - (radius), -(radius));

    CGSize size = [str sizeWithFont:[UIFont fontWithName:@"Helvetica" size:12.0]
                     constrainedToSize:rect.size
                         lineBreakMode:(NSLineBreakByWordWrapping)];

    [str drawAtPoint:CGPointMake(((radius * 2) - 10) - size.width, radius) withFont:[UIFont fontWithName:@"Helvetica" size:12.0]];


    CGContextRestoreGState(context);
}

---

for（int i=0；i这将产生所需的输出：

for (int i=0; i<24; i++) {
    CGContextSaveGState(context);
    CGContextRef context = UIGraphicsGetCurrentContext();
    NSString *str = [NSString stringWithFormat:@"Aroma %d", i];

    CGContextTranslateCTM(context, radius, radius);
    CGContextRotateCTM(context, i * 15 * M_PI/180.0);
    [[UIColor whiteColor] set];
    CGSize size = [str sizeWithFont:[UIFont fontWithName:@"Helvetica" size:12.0]
                  constrainedToSize:rect.size
                      lineBreakMode:(NSLineBreakByWordWrapping)];

    CGContextTranslateCTM(context, radius-10-size.width/2, size.height/2); // (1)
    if (i >= 7 && i <= 17)
        CGContextRotateCTM(context, M_PI); // (2)
    [str drawAtPoint:CGPointMake(-size.width/2, -size.height/2) withFont:[UIFont fontWithName:@"Helvetica" size:12.0]];

    CGContextRestoreGState(context);
}

for（inti=0；i=7&&i）这真是太棒了。如果可以的话，我会多次投票。