curved text starting point - ios

Question

I'm using this to generate a curved text:
- (UIImage*)createCircularText:(NSString*)text withSize:(CGSize)size andCenter:(CGPoint)center
{
UIFont *font = [UIFont fontWithName:#"HelveticaNeue-Light" size:15];
// Start drawing
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
// Retrieve the center and set a radius
CGFloat r = center.x / 3;
// Start by adjusting the context origin
// This affects all subsequent operations
CGContextTranslateCTM(context, center.x, center.y);
// Calculate the full extent
CGFloat fullSize = 0;
for (int i = 0; i < [text length]; i++)
{
NSString *letter = [text substringWithRange:NSMakeRange(i, 1)];
CGSize letterSize = [letter sizeWithAttributes:#{NSFontAttributeName:font}];
fullSize += letterSize.width;
}
// Initialize the consumed space
CGFloat consumedSize = 0.0f;
// Iterate through the alphabet
for (int i = 0; i < [text length]; i++)
{
// Retrieve the letter and measure its display size
NSString *letter = [text substringWithRange:NSMakeRange(i, 1)];
CGSize letterSize = [letter sizeWithAttributes:#{NSFontAttributeName:font}];
// Calculate the current angular offset
//CGFloat theta = i * (2 * M_PI / ((float)[text length] * 3));
// Move the pointer forward, calculating the new percentage of travel along the path
consumedSize += letterSize.width / 2.0f;
CGFloat percent = consumedSize / fullSize;
CGFloat theta = (percent * 2 * M_PI) / ((float)[text length] / 4);
consumedSize += letterSize.width / 2.0f;
// Encapsulate each stage of the drawing
CGContextSaveGState(context);
// Rotate the context
CGContextRotateCTM(context, theta);
// Translate up to the edge of the radius and move left by
// half the letter width. The height translation is negative
// as this drawing sequence uses the UIKit coordinate system.
// Transformations that move up go to lower y values.
CGContextTranslateCTM(context, -letterSize.width / 2, -r);
// Draw the letter and pop the transform state
[letter drawAtPoint:CGPointMake(0, 0) withAttributes:#{NSFontAttributeName:font}];
CGContextRestoreGState(context);
}
// Retrieve and return the image
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
and i get this back:
The problem is that the text starts at 0° but I actually want it to begin more at the left, so that the center of the string is at 0°. How to accomplish this?

Answer 1

Two options should work:
After drawing all of the text, rotate the context half of the use angle and get the image from the context at that point.
Make two passes. The first simply calculates the required angle to draw the text. The second pass does what you do now. Except in the 2nd pass, subtract half of the required total angle from each letter's angle.