现有圆上的曲线文字

Question

对于我正在构建的应用程序,我绘制了2个圆圈.一个比另一个大一点.我想在这些行之间弯曲文本,以便建立一个圆形菜单.

我阅读了关于弯曲文本的大部分内容,你必须将文本分成字符,然后用正确的角度绘制每个字符(通过旋转你正在绘制的上下文).

我无法绕过如何为我的角色获得正确的角度和位置.

我在屏幕截图中列出了目前菜单的样子.只有我添加的文本是从UIImageView中的图像加载的.

我希望有人可以在某些方面为我提供一些关于如何在白色圆圈中绘制文字的起点.

编辑:好的,我目前正在这一点上:

我通过使用以下代码完成:

- (UIImage*) createMenuRingWithFrame:(CGRect)frame
{
    CGRect imageSize = CGRectMake(0,0,300,300);
    float perSectionDegrees = 360 / [sections count];
    float totalRotation = 90;
    char* fontName = (char*)[self.menuItemsFont.fontName cStringUsingEncoding:NSASCIIStringEncoding];

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(NULL, imageSize.size.width, imageSize.size.height, 8, 4 * imageSize.size.width, colorSpace, kCGImageAlphaPremultipliedFirst);

    CGContextSetTextMatrix(context, CGAffineTransformIdentity);
    CGContextSelectFont(context, fontName, 18, kCGEncodingMacRoman);

    CGContextSetRGBFillColor(context, 0, 0, 0, 1);

    CGPoint centerPoint = CGPointMake(imageSize.size.width / 2, imageSize.size.height / 2);
    double radius = (frame.size.width / 2);

    CGContextStrokeEllipseInRect(context, CGRectMake(centerPoint.x - (frame.size.width / 2), centerPoint.y - (frame.size.height / 2), frame.size.width, frame.size.height));

    for (int index = 0; index < [sections count]; index++)
    {
        NSString* menuItemText = [sections objectAtIndex:index];
        CGSize textSize = [menuItemText sizeWithFont:self.menuItemsFont];
        char* menuItemTextChar = (char*)[menuItemText cStringUsingEncoding:NSASCIIStringEncoding];

        float x = centerPoint.x + radius * cos(degreesToRadians(totalRotation));
        float y = centerPoint.y + radius * sin(degreesToRadians(totalRotation));

        CGContextSaveGState(context);

        CGContextTranslateCTM(context, x, y);
        CGContextRotateCTM(context, degreesToRadians(totalRotation - 90));
        CGContextShowTextAtPoint(context, 0 - (textSize.width / 2), 0 - (textSize.height / 2), menuItemTextChar, strlen(menuItemTextChar));

        CGContextRestoreGState(context);

        totalRotation += perSectionDegrees;
    }

    CGImageRef contextImage = CGBitmapContextCreateImage(context);

    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    return [UIImage imageWithCGImage:contextImage];
}

这些是我在那里使用的变量:

NSArray* sections = [[NSArray alloc] initWithObjects:@"settings", @"test", @"stats", @"nog iets", @"woei", @"woei2", nil];
self.menuItemsFont = [UIFont fontWithName:@"VAGRounded-Bold" size:18];

单词的旋转看似正确,位置也是如此.现在我需要以某种方式弄清楚字母(和它们的坐标)应该在哪个旋转.我可以用一些帮助.

编辑:修复!看看下面的代码!

- (void) drawStringAtContext:(CGContextRef) context string:(NSString*) text atAngle:(float) angle withRadius:(float) radius
{
    CGSize textSize = [text sizeWithFont:self.menuItemsFont];

    float perimeter = 2 * M_PI * radius;
    float textAngle = textSize.width / perimeter * 2 * M_PI;

    angle += textAngle / 2;

    for (int index = 0; index < [text length]; index++)
    {
        NSRange range = {index, 1};
        NSString* letter = [text substringWithRange:range];     
        char* c = (char*)[letter cStringUsingEncoding:NSASCIIStringEncoding];
        CGSize charSize = [letter sizeWithFont:self.menuItemsFont];

        NSLog(@"Char %@ with size: %f x %f", letter, charSize.width, charSize.height);

        float x = radius * cos(angle);
        float y = radius * sin(angle);

        float letterAngle = (charSize.width / perimeter * -2 * M_PI);

        CGContextSaveGState(context);
        CGContextTranslateCTM(context, x, y);
        CGContextRotateCTM(context, (angle - 0.5 * M_PI));
        CGContextShowTextAtPoint(context, 0, 0, c, strlen(c));
        CGContextRestoreGState(context);

        angle += letterAngle;
    }
}

- (UIImage*) createMenuRingWithFrame:(CGRect)frame
{
    CGPoint centerPoint = CGPointMake(frame.size.width / 2, frame.size.height / 2);
    char* fontName = (char*)[self.menuItemsFont.fontName cStringUsingEncoding:NSASCIIStringEncoding];

    CGFloat* ringColorComponents = (float*)CGColorGetComponents(ringColor.CGColor);
    CGFloat* textColorComponents = (float*)CGColorGetComponents(textColor.CGColor);

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(NULL, frame.size.width, frame.size.height, 8, 4 * frame.size.width, colorSpace, kCGImageAlphaPremultipliedFirst);

    CGContextSetTextMatrix(context, CGAffineTransformIdentity);

    CGContextSelectFont(context, fontName, 18, kCGEncodingMacRoman);
    CGContextSetRGBStrokeColor(context, ringColorComponents[0], ringColorComponents[1], ringColorComponents[2], ringAlpha);
    CGContextSetLineWidth(context, ringWidth);  

    CGContextStrokeEllipseInRect(context, CGRectMake(ringWidth, ringWidth, frame.size.width - (ringWidth * 2), frame.size.height - (ringWidth * 2)));
    CGContextSetRGBFillColor(context, textColorComponents[0], textColorComponents[1], textColorComponents[2], textAlpha);

    CGContextSaveGState(context);
    CGContextTranslateCTM(context, centerPoint.x, centerPoint.y);

    float angleStep = 2 * M_PI / [sections count];
    float angle = degreesToRadians(90);

    textRadius = textRadius - 12;

    for (NSString* text in sections)
    {
        [self drawStringAtContext:context string:text atAngle:angle withRadius:textRadius];
        angle -= angleStep;
    }

    CGContextRestoreGState(context);

    CGImageRef contextImage = CGBitmapContextCreateImage(context);

    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);

    [self saveImage:[UIImage imageWithCGImage:contextImage] withName:@"test.png"];
    return [UIImage imageWithCGImage:contextImage];

}

Answer 1

我改编了Apple的CoreTextArcCocoa示例项目(Tom H在本回复中提到),并认为我会在这里分享.

我还添加了一些其他功能,例如将弧形大小设置为小于180的能力,以及文本颜色和偏移量作为属性(这样您就不必拥有一个巨大的框架来显示整体文本).

 /*

 File: CoreTextArcView.m (iOS version)

 Abstract: Defines and implements the CoreTextArcView custom UIView subclass to
 draw text on a curve and illustrate best practices with CoreText.

 Based on CoreTextArcView provided by Apple for Mac OS X https://developer.apple.com/library/mac/#samplecode/CoreTextArcCocoa/Introduction/Intro.html

 Ported to iOS (& added color, arcsize features) August 2011 by Alec Vance, Juggleware LLC http://juggleware.com/

 */ 

#import <UIKit/UIKit.h>
#import <CoreText/CoreText.h>


@interface CoreTextArcView : UIView {
@private
    UIFont *            _font;
    NSString *          _string;
    CGFloat             _radius;
    UIColor *           _color;
    CGFloat             _arcSize;
    CGFloat             _shiftH, _shiftV; // horiz & vertical shift

    struct {
        unsigned int    showsGlyphBounds:1;
        unsigned int    showsLineMetrics:1;
        unsigned int    dimsSubstitutedGlyphs:1;
        unsigned int    reserved:29;
    }                   _flags;
}

@property(retain, nonatomic) UIFont *font;
@property(retain, nonatomic) NSString *text;
@property(readonly, nonatomic) NSAttributedString *attributedString;
@property(assign, nonatomic) CGFloat radius;
@property(nonatomic) BOOL showsGlyphBounds;
@property(nonatomic) BOOL showsLineMetrics;
@property(nonatomic) BOOL dimsSubstitutedGlyphs;
@property(retain, nonatomic) UIColor *color;
@property(nonatomic) CGFloat arcSize;
@property(nonatomic) CGFloat shiftH, shiftV;
@end


/*

 File: CoreTextArcView.m (iOS version)

 */ 

#import "CoreTextArcView.h"
#import <AssertMacros.h>
#import <QuartzCore/QuartzCore.h>

#define ARCVIEW_DEBUG_MODE          NO

#define ARCVIEW_DEFAULT_FONT_NAME   @"Helvetica"
#define ARCVIEW_DEFAULT_FONT_SIZE   64.0
#define ARCVIEW_DEFAULT_RADIUS      150.0
#define ARCVIEW_DEFAULT_ARC_SIZE    180.0



@implementation CoreTextArcView

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        self.font = [UIFont fontWithName:ARCVIEW_DEFAULT_FONT_NAME size:ARCVIEW_DEFAULT_FONT_SIZE];
        self.text = @"Curvaceous Type";
        self.radius = ARCVIEW_DEFAULT_RADIUS;
        self.showsGlyphBounds = NO;
        self.showsLineMetrics = NO;
        self.dimsSubstitutedGlyphs = NO;
        self.color = [UIColor whiteColor];
        self.arcSize = ARCVIEW_DEFAULT_ARC_SIZE;
        self.shiftH = self.shiftV = 0.0f;
    }
    return self;
}

typedef struct GlyphArcInfo {
    CGFloat         width;
    CGFloat         angle;  // in radians
} GlyphArcInfo;

static void PrepareGlyphArcInfo(CTLineRef line, CFIndex glyphCount, GlyphArcInfo *glyphArcInfo, CGFloat arcSizeRad)
{
    NSArray *runArray = (NSArray *)CTLineGetGlyphRuns(line);

    // Examine each run in the line, updating glyphOffset to track how far along the run is in terms of glyphCount.
    CFIndex glyphOffset = 0;
    for (id run in runArray) {
        CFIndex runGlyphCount = CTRunGetGlyphCount((CTRunRef)run);

        // Ask for the width of each glyph in turn.
        CFIndex runGlyphIndex = 0;
        for (; runGlyphIndex < runGlyphCount; runGlyphIndex++) {
            glyphArcInfo[runGlyphIndex + glyphOffset].width = CTRunGetTypographicBounds((CTRunRef)run, CFRangeMake(runGlyphIndex, 1), NULL, NULL, NULL);
        }

        glyphOffset += runGlyphCount;
    }

    double lineLength = CTLineGetTypographicBounds(line, NULL, NULL, NULL);

    CGFloat prevHalfWidth = glyphArcInfo[0].width / 2.0;
    glyphArcInfo[0].angle = (prevHalfWidth / lineLength) * arcSizeRad;

    // Divide the arc into slices such that each one covers the distance from one glyph's center to the next.
    CFIndex lineGlyphIndex = 1;
    for (; lineGlyphIndex < glyphCount; lineGlyphIndex++) {
        CGFloat halfWidth = glyphArcInfo[lineGlyphIndex].width / 2.0;
        CGFloat prevCenterToCenter = prevHalfWidth + halfWidth;

        glyphArcInfo[lineGlyphIndex].angle = (prevCenterToCenter / lineLength) * arcSizeRad;

        prevHalfWidth = halfWidth;
    }
}


// ensure that redraw occurs.
-(void)setText:(NSString *)text{
    [_string release];
    _string = [text retain];

    [self setNeedsDisplay];
}

//set arc size in degrees (180 = half circle)
-(void)setArcSize:(CGFloat)degrees{
    _arcSize = degrees * M_PI/180.0;
}

//get arc size in degrees
-(CGFloat)arcSize{
    return _arcSize * 180.0/M_PI;
}

- (void)drawRect:(CGRect)rect {
    // Don't draw if we don't have a font or string
    if (self.font == NULL || self.text == NULL) 
        return;

    // Initialize the text matrix to a known value
    CGContextRef context = UIGraphicsGetCurrentContext();


    //Reset the transformation
    //Doing this means you have to reset the contentScaleFactor to 1.0
    CGAffineTransform t0 = CGContextGetCTM(context);


    CGFloat xScaleFactor = t0.a > 0 ? t0.a : -t0.a;
    CGFloat yScaleFactor = t0.d > 0 ? t0.d : -t0.d;
    t0 = CGAffineTransformInvert(t0);
    if (xScaleFactor != 1.0 || yScaleFactor != 1.0)
        t0 = CGAffineTransformScale(t0, xScaleFactor, yScaleFactor);

    CGContextConcatCTM(context, t0);

    CGContextSetTextMatrix(context, CGAffineTransformIdentity);

    if(ARCVIEW_DEBUG_MODE){
        // Draw a black background (debug)
        CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);
        CGContextFillRect(context, self.layer.bounds);
    }

    NSAttributedString *attStr = self.attributedString;
    CFAttributedStringRef asr = (CFAttributedStringRef)attStr;
    CTLineRef line = CTLineCreateWithAttributedString(asr);
    assert(line != NULL);

    CFIndex glyphCount = CTLineGetGlyphCount(line);
    if (glyphCount == 0) {
        CFRelease(line);
        return;
    }

    GlyphArcInfo *  glyphArcInfo = (GlyphArcInfo*)calloc(glyphCount, sizeof(GlyphArcInfo));
    PrepareGlyphArcInfo(line, glyphCount, glyphArcInfo, _arcSize);

    // Move the origin from the lower left of the view nearer to its center.
    CGContextSaveGState(context);

    CGContextTranslateCTM(context, CGRectGetMidX(rect)+_shiftH, CGRectGetMidY(rect)+_shiftV - self.radius / 2.0);

    if(ARCVIEW_DEBUG_MODE){
        // Stroke the arc in red for verification.
        CGContextBeginPath(context);
        CGContextAddArc(context, 0.0, 0.0, self.radius, M_PI_2+_arcSize/2.0, M_PI_2-_arcSize/2.0, 1);
        CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);
        CGContextStrokePath(context);
    }

    // Rotate the context 90 degrees counterclockwise (per 180 degrees)
    CGContextRotateCTM(context, _arcSize/2.0);

    // Now for the actual drawing. The angle offset for each glyph relative to the previous glyph has already been calculated; with that information in hand, draw those glyphs overstruck and centered over one another, making sure to rotate the context after each glyph so the glyphs are spread along a semicircular path.

    CGPoint textPosition = CGPointMake(0.0, self.radius);
    CGContextSetTextPosition(context, textPosition.x, textPosition.y);

    CFArrayRef runArray = CTLineGetGlyphRuns(line);
    CFIndex runCount = CFArrayGetCount(runArray);

    CFIndex glyphOffset = 0;
    CFIndex runIndex = 0;
    for (; runIndex < runCount; runIndex++) {
        CTRunRef run = (CTRunRef)CFArrayGetValueAtIndex(runArray, runIndex);
        CFIndex runGlyphCount = CTRunGetGlyphCount(run);
        Boolean drawSubstitutedGlyphsManually = false;
        CTFontRef runFont = CFDictionaryGetValue(CTRunGetAttributes(run), kCTFontAttributeName);

        // Determine if we need to draw substituted glyphs manually. Do so if the runFont is not the same as the overall font.
        if (self.dimsSubstitutedGlyphs && ![self.font isEqual:(UIFont *)runFont]) {
            drawSubstitutedGlyphsManually = true;
        }

        CFIndex runGlyphIndex = 0;
        for (; runGlyphIndex < runGlyphCount; runGlyphIndex++) {
            CFRange glyphRange = CFRangeMake(runGlyphIndex, 1);
            CGContextRotateCTM(context, -(glyphArcInfo[runGlyphIndex + glyphOffset].angle));

            // Center this glyph by moving left by half its width.
            CGFloat glyphWidth = glyphArcInfo[runGlyphIndex + glyphOffset].width;
            CGFloat halfGlyphWidth = glyphWidth / 2.0;
            CGPoint positionForThisGlyph = CGPointMake(textPosition.x - halfGlyphWidth, textPosition.y);

            // Glyphs are positioned relative to the text position for the line, so offset text position leftwards by this glyph's width in preparation for the next glyph.
            textPosition.x -= glyphWidth;

            CGAffineTransform textMatrix = CTRunGetTextMatrix(run);
            textMatrix.tx = positionForThisGlyph.x;
            textMatrix.ty = positionForThisGlyph.y;
            CGContextSetTextMatrix(context, textMatrix);

            if (!drawSubstitutedGlyphsManually) {
                CTRunDraw(run, context, glyphRange);
            } 
            else {
                // We need to draw the glyphs manually in this case because we are effectively applying a graphics operation by setting the context fill color. Normally we would use kCTForegroundColorAttributeName, but this does not apply as we don't know the ranges for the colors in advance, and we wanted demonstrate how to manually draw.
                CGFontRef cgFont = CTFontCopyGraphicsFont(runFont, NULL);
                CGGlyph glyph;
                CGPoint position;

                CTRunGetGlyphs(run, glyphRange, &glyph);
                CTRunGetPositions(run, glyphRange, &position);

                CGContextSetFont(context, cgFont);
                CGContextSetFontSize(context, CTFontGetSize(runFont));
                CGContextSetRGBFillColor(context, 0.25, 0.25, 0.25, 0.5);
                CGContextShowGlyphsAtPositions(context, &glyph, &position, 1);

                CFRelease(cgFont);
            }

            // Draw the glyph bounds 
            if ((self.showsGlyphBounds) != 0) {
                CGRect glyphBounds = CTRunGetImageBounds(run, context, glyphRange);

                CGContextSetRGBStrokeColor(context, 0.0, 0.0, 1.0, 1.0);
                CGContextStrokeRect(context, glyphBounds);
            }
            // Draw the bounding boxes defined by the line metrics
            if ((self.showsLineMetrics) != 0) {
                CGRect lineMetrics;
                CGFloat ascent, descent;

                CTRunGetTypographicBounds(run, glyphRange, &ascent, &descent, NULL);

                // The glyph is centered around the y-axis
                lineMetrics.origin.x = -halfGlyphWidth;
                lineMetrics.origin.y = positionForThisGlyph.y - descent;
                lineMetrics.size.width = glyphWidth; 
                lineMetrics.size.height = ascent + descent;

                CGContextSetRGBStrokeColor(context, 0.0, 1.0, 0.0, 1.0);
                CGContextStrokeRect(context, lineMetrics);
            }
        }

        glyphOffset += runGlyphCount;
    }

    CGContextRestoreGState(context);

    free(glyphArcInfo);
    CFRelease(line);    



}

-(void)dealloc
{
    [_font release];
    [_string release];
    [_color release];
    [super dealloc]
}

@synthesize font = _font;
@synthesize text = _string;
@synthesize radius = _radius;
@synthesize color = _color;
@synthesize arcSize = _arcSize;
@synthesize shiftH = _shiftH;
@synthesize shiftV = _shiftV;

@dynamic attributedString;
- (NSAttributedString *)attributedString {
    // Create an attributed string with the current font and string.
    assert(self.font != nil);
    assert(self.text != nil);

    // Create our attributes...

    // font
    CTFontRef fontRef = CTFontCreateWithName((CFStringRef)self.font.fontName, self.font.pointSize, NULL);

    // color
    CGColorRef colorRef = self.color.CGColor;

    // pack it into attributes dictionary

    NSDictionary *attributesDict = [NSDictionary dictionaryWithObjectsAndKeys:
                                    (id)fontRef, (id)kCTFontAttributeName,
                                    colorRef, (id)kCTForegroundColorAttributeName,
                                    nil];
    assert(attributesDict != nil);


    // Create the attributed string
    NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:self.text attributes:attributesDict];

    CFRelease(fontRef);

    return [attrString autorelease];
}

@dynamic showsGlyphBounds;
- (BOOL)showsGlyphBounds {
    return _flags.showsGlyphBounds;
}

- (void)setShowsGlyphBounds:(BOOL)show {
    _flags.showsGlyphBounds = show ? 1 : 0;
}

@dynamic showsLineMetrics;
- (BOOL)showsLineMetrics {
    return _flags.showsLineMetrics;
}

- (void)setShowsLineMetrics:(BOOL)show {
    _flags.showsLineMetrics = show ? 1 : 0;
}

@dynamic dimsSubstitutedGlyphs;
- (BOOL)dimsSubstitutedGlyphs {
    return _flags.dimsSubstitutedGlyphs;
}

- (void)setDimsSubstitutedGlyphs:(BOOL)dim {
    _flags.dimsSubstitutedGlyphs = dim ? 1 : 0;
}

@end

Answer 2

我试图在纸上快速解决,所以我可能错了:)

将字符串的长度转换为UnitCircle上的单位.因此(string.lenght/circle perimeter)*2Pi.您现在拥有整个字符串的弧度角度.(这是字符串开头和结尾之间的角度)

对于单独的字母,您可以执行相同的操作以获得单个字母的角度(以弧度表示)(使用字母宽度)

一旦你有弧度的角度,你可以计算字母的x和y位置(和旋转).

额外奖励:对于均匀间距,您甚至可以计算出所有琴弦的总长度与整个周长之间的比例.并在字符串之间平均分配剩余空间.

更新 我使用html5/canvas 进行了概念验证,因此使用合适的浏览器查看它:)您应该能够移植它.(请注意,代码未注释)
wtf:代码在chrome调试控制台打开时运行正常,并在关闭时失败.(解决方法:打开chrome控制台:ctrl-shift-j并重新加载页面:f5); FF3.6.8好像很好,但字母'跳舞'.

Answer 3

为了节省您的时间,这里是我发现的CoreTextArcView公开的内容

- (id)initWithFrame:(CGRect)frame font:(UIFont *)font text:(NSString *)text radius:(float)radius arcSize:(float)arcSize color:(UIColor *)color;

  (x,y)<---------------     w             --------------->
      +--------------------------------------------------+
     ^|                                                  |  <--
     ||                                                  |  frame
     ||                                                  |
     ||                 VED L A BEL                      |
     ||             CU R            HE                   |
     ||           xx                   RE  x             |
      |          xx                        xxx           |
      |        xxx xx                     x   xxx        |
    h |      xxx    xx                  xxx     xx       |
      |      x       xxx         <-----------------------------
      |     xx         xx   xxxxxxx   xx           x     |  arcSize :
     ||    xx            xxx       xxx             xx    |  opening angle
     ||    x              xxx      xx               x    |  in degrees
     ||   xx                xx  xxx                 x    |
     ||   x  <---- r  ----->   x                    x    |
     ||   x                      (xc,yc)            x    |
     ||   x                             <-----------------------
     ||   x                                        xx    |  xc = x + w /2
     v+---xx--------------------------------------xx-----+  yc = y + h /2 + r /2
           xx                                    xx
            x                                   xx
            xxx                                xx
              xxx                            xxx
                xxxx                      xxxx
                   xxxxx              xxxxx
                        xxxxxxxxxxxxxxx

这对r> 0和arcsize> 0有效.

Answer 4

看看这个Apple示例项目: CoreTextArcCocoa

演示如何使用Core Text在Cocoa应用程序中沿弧绘制文本.此外,此示例说明了如何使用Cocoa字体面板接收可由Core Text用于选择用于绘制的字体的字体设置.

CoreText也可在iOS中使用,因此您应该能够实现类似的功能.

Answer 5

这是我的方法，用于以预定义的角度（以弧度为单位）在层上绘制弯曲的属性字符串：

[self drawCurvedStringOnLayer:self.layer withAttributedText:incident atAngle:angle withRadius:300];

字符串也会在圆弧的底部自动反转。

- (void)drawCurvedStringOnLayer:(CALayer *)layer
             withAttributedText:(NSAttributedString *)text
                        atAngle:(float)angle
                     withRadius:(float)radius {

    // angle in radians

    CGSize textSize = CGRectIntegral([text boundingRectWithSize:CGSizeMake(CGFLOAT_MAX, CGFLOAT_MAX)
                                                        options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading)
                                                        context:nil]).size;

    float perimeter = 2 * M_PI * radius;
    float textAngle = (textSize.width / perimeter * 2 * M_PI); 

    float textRotation;
    float textDirection;
    if (angle > degreesToRadians(10) && angle < degreesToRadians(170)) {
        //bottom string
        textRotation = 0.5 * M_PI ;
        textDirection = - 2 * M_PI;
        angle += textAngle / 2;
    } else {
        //top string
        textRotation = 1.5 * M_PI ;
        textDirection = 2 * M_PI;
        angle -= textAngle / 2;
    }

    for (int c = 0; c < text.length; c++) {
        NSRange range = {c, 1};
        NSAttributedString* letter = [text attributedSubstringFromRange:range];
        CGSize charSize = CGRectIntegral([letter boundingRectWithSize:CGSizeMake(CGFLOAT_MAX, CGFLOAT_MAX)
                                                              options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading)
                                                              context:nil]).size;

        float letterAngle = ( (charSize.width / perimeter) * textDirection );

        float x = radius * cos(angle + (letterAngle/2));
        float y = radius * sin(angle + (letterAngle/2));

        CATextLayer *singleChar = [self drawTextOnLayer:layer
                                           withText:letter
                                              frame:CGRectMake(layer.frame.size.width/2 - charSize.width/2 + x,
                                                               layer.frame.size.height/2 - charSize.height/2 + y,
                                                               charSize.width, charSize.height)
                                            bgColor:nil
                                            opacity:1];

        singleChar.transform = CATransform3DMakeAffineTransform( CGAffineTransformMakeRotation(angle - textRotation) );

        angle += letterAngle;
    }
}


- (CATextLayer *)drawTextOnLayer:(CALayer *)layer
                        withText:(NSAttributedString *)text
                           frame:(CGRect)frame
                         bgColor:(UIColor *)bgColor
                         opacity:(float)opacity {

    CATextLayer *textLayer = [[CATextLayer alloc] init];
    [textLayer setFrame:frame];
    [textLayer setString:text];
    [textLayer setAlignmentMode:kCAAlignmentCenter];
    [textLayer setBackgroundColor:bgColor.CGColor];
    [textLayer setContentsScale:[UIScreen mainScreen].scale];
    [textLayer setOpacity:opacity];
    [layer addSublayer:textLayer];
    return textLayer;
}


/** Degrees to Radian **/
#define degreesToRadians(degrees) (( degrees ) / 180.0 * M_PI )

/** Radians to Degrees **/
#define radiansToDegrees(radians) (( radians ) * ( 180.0 / M_PI ) )