Drawing filled circles with letters in iOS 7

Question

The new ios 7 phone app has a favorites section. In that section the names of the contact appear next to a filled in circle with the inital of the contact inside the circle.

How is this drawn? With drawrect or is there already and object created for this?

Answer 1

Below is a UIView subclass that will do what you want. It will correctly size and position 1 or more letters in the circle. Here's how it looks with 1-3 letters at various sizes (32, 64, 128, 256):

With the availability of user defined runtime attributes in Interface Builder, you can even configure the view from within IB. Just set the text property as a runtime attribute and the backgroundColor to the color you want for the circle.

Here's the code:

@interface MELetterCircleView : UIView

/**
 * The text to display in the view. This should be limited to 
 * just a few characters.
 */
@property (nonatomic, strong) NSString *text;

@end



@interface MELetterCircleView ()

@property (nonatomic, strong) UIColor *circleColor;

@end

@implementation MELetterCircleView

- (instancetype)initWithFrame:(CGRect)frame text:(NSString *)text
{
    NSParameterAssert(text);
    self = [super initWithFrame:frame];
    if (self)
    {
        self.text = text;
    }

    return self;
}

// Override to set the circle's background color. 
// The view's background will always be clear.
-(void)setBackgroundColor:(UIColor *)backgroundColor
{
    self.circleColor = backgroundColor;
    [super setBackgroundColor:[UIColor clearColor]];
}


- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();

    [self.circleColor setFill];
    CGContextAddArc(context, CGRectGetMidX(rect), CGRectGetMidY(rect),
                             CGRectGetWidth(rect)/2, 0, 2*M_PI, YES);
    CGContextFillPath(context);

    [self drawSubtractedText:self.text inRect:rect inContext:context];

}

- (void)drawSubtractedText:(NSString *)text inRect:(CGRect)rect 
                 inContext:(CGContextRef)context
{
    CGContextSaveGState(context);

    // Magic blend mode
    CGContextSetBlendMode(context, kCGBlendModeDestinationOut);


    CGFloat pointSize = 
           [self optimumFontSizeForFont:[UIFont boldSystemFontOfSize:100.f]
                                 inRect:rect 
                               withText:text];

    UIFont *font = [UIFont boldSystemFontOfSize:pointSize];

    // Move drawing start point for centering label.
    CGContextTranslateCTM(context, 0, 
                           (CGRectGetMidY(rect) - (font.lineHeight/2)));

    CGRect frame = CGRectMake(0, 0, CGRectGetWidth(rect), font.lineHeight)];
    UILabel *label = [[UILabel alloc] initWithFrame:frame];
    label.font = font;
    label.text = text;
    label.textAlignment = NSTextAlignmentCenter;
    label.backgroundColor = [UIColor clearColor];
    [label.layer drawInContext:context];

    // Restore the state of other drawing operations
    CGContextRestoreGState(context);
}

-(CGFloat)optimumFontSizeForFont:(UIFont *)font inRect:(CGRect)rect 
                        withText:(NSString *)text
{
    // For current font point size, calculate points per pixel
    CGFloat pointsPerPixel = font.lineHeight / font.pointSize;

    // Scale up point size for the height of the label. 
    // This represents the optimum size of a single letter.
    CGFloat desiredPointSize = rect.size.height * pointsPerPixel;

    if ([text length] == 1)
    {
            // In the case of a single letter, we need to scale back a bit
            //  to take into account the circle curve.
            // We could calculate the inner square of the circle, 
            // but this is a good approximation.
        desiredPointSize = .80*desiredPointSize;
    }
    else
    {
        // More than a single letter. Let's make room for more.
        desiredPointSize = desiredPointSize / [text length];
    }

    return desiredPointSize;
}
@end