CenteredPathView

CenteredPathView.m

// Draws a CGPath scaled to fix exactly within the view.
// Created by Monte Hurd on 8/26/14.

// CenteredPathView.h

#import <UIKit/UIKit.h>

@interface CenteredPathView : UIView

-(id)initWithPath: (CGPathRef)newPath
      strokeWidth: (CGFloat)strokeWidth
      strokeColor: (UIColor *)strokeColor
        fillColor: (UIColor *)fillColor;
@end


// CenteredPathView.m

#import "CenteredPathView.h"

@interface CenteredPathView()

@property (nonatomic) CGPathRef path;
@property (nonatomic) CGFloat strokeWidth;
@property (strong, nonatomic) UIColor *strokeColor;
@property (strong, nonatomic) UIColor *fillColor;

@end

@implementation CenteredPathView

-(id)initWithPath: (CGPathRef)newPath
      strokeWidth: (CGFloat)strokeWidth
      strokeColor: (UIColor *)strokeColor
        fillColor: (UIColor *)fillColor;
{
    self = [super init];
    if (self) {
        self.path = newPath;
        self.strokeWidth = strokeWidth;
        self.strokeColor = strokeColor;
        self.fillColor = fillColor;
    }
    return self;
}

- (void)drawRect:(CGRect)rect
{
    CGPathRef path = self.path;
    
    CGRect boundingBox = CGPathGetBoundingBox(path);
    
    // Translate path to origin zero zero.
    CGAffineTransform zeroZeroXF = CGAffineTransformMakeTranslation(-boundingBox.origin.x, -boundingBox.origin.y);
    path = CGPathCreateCopyByTransformingPath(path, &zeroZeroXF);
    boundingBox = CGPathGetBoundingBox(path);
    
    // Fitting / Centering code below based on: http://stackoverflow.com/a/15936794
    
    // Calculate scale to fit path in rect.
    CGFloat boundingBoxAspectRatio = CGRectGetWidth(boundingBox)/CGRectGetHeight(boundingBox);
    CGFloat viewAspectRatio = CGRectGetWidth(rect)/CGRectGetHeight(rect);
    CGFloat scaleFactor = 1.0;
    if (boundingBoxAspectRatio > viewAspectRatio) {
        scaleFactor = (CGRectGetWidth(rect)-(self.strokeWidth * 2.0f)) / CGRectGetWidth(boundingBox);
    } else {
        scaleFactor = (CGRectGetHeight(rect)-(self.strokeWidth * 2.0f)) / CGRectGetHeight(boundingBox);
    }
    
    // Apply new scale to path.
    CGAffineTransform scaleTransform = CGAffineTransformIdentity;
    scaleTransform = CGAffineTransformScale(scaleTransform, scaleFactor, scaleFactor);
    scaleTransform = CGAffineTransformTranslate(scaleTransform, -CGRectGetMinX(boundingBox), -CGRectGetMinY(boundingBox));
    
    // Calculate transform to center newly scaled path in rect.
    CGSize scaledSize = CGSizeApplyAffineTransform(boundingBox.size, CGAffineTransformMakeScale(scaleFactor, scaleFactor));
    CGSize centerOffset = CGSizeMake((CGRectGetWidth(rect) - scaledSize.width)/(scaleFactor * 2.0),
                                     (CGRectGetHeight(rect) - scaledSize.height)/(scaleFactor * 2.0));
    scaleTransform = CGAffineTransformTranslate(scaleTransform, centerOffset.width, centerOffset.height);
    
    // Apply centering transform.
    CGPathRef scaledPath = CGPathCreateCopyByTransformingPath(path, &scaleTransform);
    
    // Draw!
	CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGContextSetLineWidth(ctx, self.strokeWidth);
    [self.fillColor setFill];
    [self.strokeColor setStroke];
    CGContextAddPath(ctx, scaledPath);
    CGContextDrawPath(ctx, kCGPathFillStroke);
    
    CGPathRelease(scaledPath); // release the copied path
}

@end