Draw Angled/Rotated MultiLine Text - Core Text + Core Graphics

core-graphics, core-text, ios, iphone, objective-c

Solution

Apply the rotation to the context before drawing the `CTFrameRef` into it.

Edit : If you want multiple angles, you need to save/restore the graphics states, each time. Something like :

- (void)drawRect:(CGRect)rect
{
    NSString *text = @"This is some text being drawn by CoreText!\nAnd some more text on another line!";

    //Core Text (Create Attributed String)

    UIColor *textColor = [UIColor blackColor];
    CGColorRef color = textColor.CGColor;

    CTFontRef font = CTFontCreateWithName((CFStringRef) @"HelveticaNeue", 20.0, NULL);

    CTTextAlignment theAlignment = kCTTextAlignmentLeft;

    CFIndex theNumberOfSettings = 1;
    CTParagraphStyleSetting theSettings[1] =
    {
        { kCTParagraphStyleSpecifierAlignment, sizeof(CTTextAlignment),
            &theAlignment }
    };

    CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(theSettings, theNumberOfSettings);

    NSDictionary *attributesDict = [NSDictionary dictionaryWithObjectsAndKeys:
                                    CFBridgingRelease(font), (NSString *)kCTFontAttributeName,
                                    color, (NSString *)kCTForegroundColorAttributeName,
                                    paragraphStyle, (NSString *) kCTParagraphStyleAttributeName,
                                    nil];


    NSAttributedString *stringToDraw = [[NSAttributedString alloc] initWithString:text attributes:attributesDict];

    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)stringToDraw);

    //Create Frame
    CGMutablePathRef path = CGPathCreateMutable();
    CGRect frameText = CGRectMake(60, 100, 200, 200);
    CGPathAddRect(path, NULL, frameText);

    CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), path, NULL);
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    CGContextSaveGState(ctx); /* save Graphic State for context rotation */

    // transform (rotate) context
    CGAffineTransform transform = CGAffineTransformMakeTranslation(self.bounds.size.width / 2.f, self.bounds.size.height / 2.f);
    CGFloat rotation = -M_PI / 2.f;
    transform = CGAffineTransformRotate(transform,rotation);
    transform = CGAffineTransformTranslate(transform,-self.bounds.size.width / 2.f, -self.bounds.size.height / 2.f);
    CGContextConcatCTM(ctx, transform);

    CGContextSaveGState(ctx);

    CGContextSetTextMatrix(ctx, CGAffineTransformIdentity);
    CGContextTranslateCTM(ctx, 0, ([self bounds]).size.height );
    CGContextScaleCTM(ctx, 1.0, -1.0);

    //Draw Frame

    CTFrameDraw(frame, ctx);
    //Release all retained objects
    CFRelease(path);

    CGContextRestoreGState(ctx);

    CGContextRestoreGState(ctx); /* restore Graphic State for context rotation */

     CGContextSaveGState(ctx); /* save Graphic States for another drawing */

     /* lets draw another string with different angle */
     attributesDict = [NSDictionary dictionaryWithObjectsAndKeys:
                                CFBridgingRelease(CTFontCreateWithName((CFStringRef) @"HelveticaNeue", 14.0, NULL)), (NSString *)kCTFontAttributeName,
                                [UIColor yellowColor].CGColor, (NSString *)kCTForegroundColorAttributeName,
                                nil];


     stringToDraw = [[NSAttributedString alloc] initWithString:@"another piece of text to drawn on same context with no angle" attributes:attributesDict];

     framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)stringToDraw);

     path = CGPathCreateMutable();
     CGPathAddRect(path, NULL, CGRectMake(60, -100, 200, 200));

     frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), path, NULL);
     CFRelease(path);
     CGContextSetTextMatrix(ctx, CGAffineTransformIdentity);
     CGContextTranslateCTM(ctx, 0, ([self bounds]).size.height );
     CGContextScaleCTM(ctx, 1.0, -1.0);

     CTFrameDraw(frame, ctx);

     /**
      * @note don't forget to restore a previously saved GState, or this will be source of problems
      */
     CGContextRestoreGState(ctx);

     CFRelease(frame);
     CFRelease(framesetter);
}

Problem

After going through several blogs & forums I didn't find an appropriate solution for drawing inclined/angled text using core Text on a views context. So here is how it goes. I have a view whose `- (void)drawRect:(CGRect)rect` is invoked to draw a string (multi or single line text) on screen. CODE: ``` - (void)drawRect:(CGRect)rect { NSString *text = @"This is some text being drawn by CoreText!\nAnd some more text on another line!"; //Core Text (Create Attributed String) UIColor *textColor = [UIColor blackColor]; CGColorRef color = textColor.CGColor; CTFontRef font = CTFontCreateWithName((CFStringRef) @"HelveticaNeue", 20.0, NULL); CTTextAlignment theAlignment = kCTTextAlignmentLeft; CFIndex theNumberOfSettings = 1; CTParagraphStyleSetting theSettings[1] = { { kCTParagraphStyleSpecifierAlignment, sizeof(CTTextAlignment), &theAlignment } }; CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(theSettings, theNumberOfSettings); NSDictionary *attributesDict = [NSDictionary dictionaryWithObjectsAndKeys: CFBridgingRelease(font), (NSString *)kCTFontAttributeName, color, (NSString *)kCTForegroundColorAttributeName, paragraphStyle, (NSString *) kCTParagraphStyleAttributeName, nil]; NSAttributedString *stringToDraw = [[NSAttributedString alloc] initWithString:text attributes:attributesDict]; CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)stringToDraw); //Create Frame CGMutablePathRef path = CGPathCreateMutable(); CGAffineTransform transform = CGAffineTransformMakeScale(1, -1); //First translate your image View according to transform transform = CGAffineTransformTranslate(transform, 0, - self.bounds.size.height); // Then whenever you want any point according to UIKit related coordinates apply this transformation on the point or rect. CGRect frameText = CGRectMake(60, 100, 200, 200); CGRect newRectForUIKit = CGRectApplyAffineTransform(frameText, transform); CGPathAddRect(path, NULL, newRectForUIKit); CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), path, NULL); CGContextRef ctx = UIGraphicsGetCurrentContext(); CGContextSetTextMatrix(ctx, CGAffineTransformIdentity); CGContextTranslateCTM(ctx, 0, ([self bounds]).size.height ); CGContextScaleCTM(ctx, 1.0, -1.0); //Draw Frame CTFrameDraw(frame, ctx); //Release all retained objects CFRelease(path); } ``` Output: Apart from drawing text I want to add an angle to the entire drawn text. Something like this(Required output) So how do I add an rotation angle to the drawn text in core text? Note: 1)A single context can have multiple drawn text objects with their respective angles as shown below I hope my question is clear.

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