iphone - Drawing rotated text with NSString drawInRect

Question

I found this answer on how to draw rotated text with NSString drawInRect:, but I'm not sure how it works since it only sort of works for me: https://discussions.apple.com/thread/1779814?start=0&tstart=0

My code looks like:

           CGContextSaveGState(context);
           CGContextDrawLinearGradient(context, gradient, CGPointMake(0, centY - halfWidth), CGPointMake(0, centY + halfWidth), 0);

            // Add text                
            CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor); 
            NSString *str = @"some test string";

            CGAffineTransform transform1 = CGAffineTransformMakeRotation(M_PI/4);

            CGContextConcatCTM(context, transform1);
            CGContextTranslateCTM(context, 0, 0);
            UIFont *font = [UIFont systemFontOfSize:16.0];

            [str drawInRect:CGRectMake(0, 0, 200, 100) withFont:font lineBreakMode:UILineBreakModeWordWrap alignment:UIBaselineAdjustmentNone];

So when I use this, I see text being drawn 45 degrees below the x-axis. I want to draw the text vertically along my lineargradient. So I thought I could do that by using M_PI/2 for 90 degrees. I do not see my text though. I have tried different transforms for the rotation, and only some seem to work like M_PI/4 and M_PI/8. I would think that if I used -M_PI/4 it would have the text 45 degrees above the x-axis and M_PI/2 would be 90 degrees below the x-axis. But both turn up with nothing.

Any thoughts? thanks.

Answer 1

I solve this problem in next way.

1) Declare category on NSString

@interface NSString (NMSchemeItemDraw)
-(void)  drawWithBasePoint:(CGPoint)basePoint
                    andAngle:(CGFloat)angle
                     andFont:(UIFont*)font;
@end

This category will draw text with given central point, in one line and with given font and angle.

2) Implementation of this category is looks like:

@implementation NSString (NMSchemeItemDraw)

    -(void)  drawWithBasePoint:(CGPoint)basePoint
                     andAngle:(CGFloat)angle
                      andFont:(UIFont *)font{
    CGSize  textSize    =   [self   sizeWithFont:font];

    CGContextRef    context =   UIGraphicsGetCurrentContext();
    CGAffineTransform   t   =   CGAffineTransformMakeTranslation(basePoint.x, basePoint.y);
    CGAffineTransform   r   =   CGAffineTransformMakeRotation(angle);


    CGContextConcatCTM(context, t);
    CGContextConcatCTM(context, r);

    [self   drawAtPoint:CGPointMake(-1 * textSize.width / 2, -1 * textSize.height / 2)
               withFont:font];

    CGContextConcatCTM(context, CGAffineTransformInvert(r));
    CGContextConcatCTM(context, CGAffineTransformInvert(t));
    }
@end

3) Now i can use it in my [UIView drawRect:] method. For example, in a next way:

 -(void)drawRect:(CGRect)rect{
 NSString* example = @"Title";
 [example drawWithBasePoint:CGPointMake(0.0f, 0.0f)
                   andAngle:M_PI
                    andFont:[UIFont boldSystemFontOfSize:16.0]];
 }