CFStringRef change color in Objective-c

Question

Is it possible to change the color for a CFStringRef?

I want to have the text red for example, by default is black, how can I change this?

I tried this:

  -(void)drawText:(NSString*)textToDraw inFrame:(CGRect)frameRect
{
    CFStringRef stringRef = (__bridge CFStringRef)textToDraw;
    // Prepare the text using a Core Text Framesetter
    CFAttributedStringRef currentText = CFAttributedStringCreate(NULL, stringRef, NULL);
    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(currentText);

    CGMutablePathRef framePath = CGPathCreateMutable();
    CGPathAddRect(framePath, NULL, frameRect);

    CFMutableAttributedStringRef attrString = CFAttributedStringCreateMutable(kCFAllocatorDefault, 0);
    CFAttributedStringReplaceString (attrString,CFRangeMake(0, 0), stringRef);

    CGColorRef _red=[UIColor redColor].CGColor;
    
    CFAttributedStringSetAttribute(attrString, CFRangeMake(0, [textToDraw length]),kCTForegroundColorAttributeName, _red);

    // Get the frame that will do the rendering.
    CFRange currentRange = CFRangeMake(0, 0);
    CTFrameRef frameRef = CTFramesetterCreateFrame(framesetter, currentRange, framePath, NULL);
    CGPathRelease(framePath);
    
    // Get the graphics context.
    CGContextRef    currentContext = UIGraphicsGetCurrentContext();
    
    // Put the text matrix into a known state. This ensures
    // that no old scaling factors are left in place.
    CGContextSetTextMatrix(currentContext, CGAffineTransformIdentity);

    // Core Text draws from the bottom-left corner up, so flip
    // the current transform prior to drawing.
    CGContextTranslateCTM(currentContext, 0, frameRect.origin.y*2);
    CGContextScaleCTM(currentContext, 1.0, -1.0);
    
    // Draw the frame.
    CTFrameDraw(frameRef, currentContext);
    
    CGContextScaleCTM(currentContext, 1.0, -1.0);
    CGContextTranslateCTM(currentContext, 0, (-1)*frameRect.origin.y*2);

    CFRelease(frameRef);
    CFRelease(stringRef);
    CFRelease(framesetter);
}

But the text is black.

please check http://stackoverflow.com/questions/13738149/change-color-a-part-text-of-sentence-in-ios — Nitin Gohel, Jun 22 '15 at 13:29
A String has no color, you have to use a AttributedString, as suggested in linked question from comment. What is not working from the previous answer? — Larme, Jun 22 '15 at 15:06
You're setting `red color effect` at range 0,0. Does it seems right to you? — Larme, Jun 22 '15 at 15:24
It didn't crash on my test (I just removed the frameThings that are not related). What range did you use? What the value of `[textToDraw length]`? If you want to color the whole text, you should on the last line `CFRangeMake(0, [textToDraw length])`, or `CFRangeMake(0, CFStringGetLength(stringRef)`. — Larme, Jun 22 '15 at 15:34
I don't use CoreText, but you seems to use `framesetter`, but initialize it with `currentText` (which has no notion of red) instead of `attrString`. Could be the issue. — Larme, Jun 22 '15 at 15:43
Well, it means that is working right? You never said which part you want to color in red. Then you have to apply correctly to the range you want. — Larme, Jun 22 '15 at 16:12

score 0 · Answer 1 · answered Jun 22 '15 at 16:45

I've edited your code for your purpose

-(void)drawText:(NSString*)textToDraw
      withColor: (UIColor*) color
        inFrame:(CGRect)frameRect
{


    CFStringRef stringRef = (__bridge CFStringRef)textToDraw;
    // Prepare the text using a Core Text Framesetter

    CGMutablePathRef framePath = CGPathCreateMutable();
    CGPathAddRect(framePath, NULL, frameRect);

    /// ATTRIBUTES FOR COLOURED STRING
    NSDictionary *attrs = @{ NSForegroundColorAttributeName : color };
    NSAttributedString *attString = [[NSAttributedString alloc] initWithString:textToDraw attributes:attrs];

    CTFramesetterRef framesetter =
    CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attString); //3
    CTFrameRef frameRef =
    CTFramesetterCreateFrame(framesetter,
                             CFRangeMake(0, [attString length]), framePath, NULL);


    // Get the graphics context.
    CGContextRef    currentContext = UIGraphicsGetCurrentContext();

    // Put the text matrix into a known state. This ensures
    // that no old scaling factors are left in place.
    CGContextSetTextMatrix(currentContext, CGAffineTransformIdentity);


    // Core Text draws from the bottom-left corner up, so flip
    // the current transform prior to drawing.
    CGContextTranslateCTM(currentContext, 0, frameRect.origin.y*2);
    CGContextScaleCTM(currentContext, 1.0, -1.0);

    // Draw the frame.
    CTFrameDraw(frameRef, currentContext);

    CGContextScaleCTM(currentContext, 1.0, -1.0);
    CGContextTranslateCTM(currentContext, 0, (-1)*frameRect.origin.y*2);


    CFRelease(frameRef);
    CFRelease(stringRef);
    CFRelease(framesetter);
}

Hope this helps.

CFStringRef change color in Objective-c

1 Answers1