joeltrew / gradientpathrenderer Goto Github PK

@implementation GradientPolylineRender

- (instancetype)initWithPolyline:(MKPolyline*)polyline colors:(NSMutableArray*)colors {
    if (self = [super initWithOverlay:polyline]) {
        self.polyline = polyline;
        self.colors = [[NSMutableArray alloc] init];
        for (int i = 0; i < colors.count; i++) {
            [self.colors addObject:(id)[colors[i] CGColor]];
        }
    }
    return self;
}

- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CGContextRef)context {
    CGFloat baseWidth = self.lineWidth / zoomScale;
    if (self.border) {
        CGContextSetLineWidth(context , baseWidth * 2);
        CGContextSetLineJoin(context, kCGLineJoinRound);
        CGContextSetLineCap(context, kCGLineCapRound);
        CGContextAddPath(context, self.path);
        if (self.borderColor) {
            CGContextSetStrokeColorWithColor(context, self.borderColor.CGColor);
        } else {
            CGContextSetStrokeColorWithColor(context, [UIColor whiteColor].CGColor);
        }
        CGContextStrokePath(context);
    }
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGFloat locations[2] = {0, 1};
    CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (CFArrayRef)self.colors, locations);
    CGContextSetLineWidth(context, baseWidth);
    CGContextSetLineJoin(context, kCGLineJoinRound);
    CGContextSetLineCap(context, kCGLineCapRound);
    CGContextAddPath(context, self.path);
    
    CGContextSaveGState(context);
    CGContextReplacePathWithStrokedPath(context);
    CGContextClip(context);
    
    CGRect boundingBox = CGPathGetBoundingBox(self.path);
    CGPoint start = boundingBox.origin;
    CGPoint end = CGPointMake(CGRectGetMaxX(boundingBox), CGRectGetMaxY(boundingBox));
    CGContextDrawLinearGradient(context, gradient, start, end, kCGGradientDrawsBeforeStartLocation);
    CGContextRestoreGState(context);
    [super drawMapRect:mapRect zoomScale:zoomScale inContext:context];
}

- (void)createPath {
    CGMutablePathRef path = CGPathCreateMutable();
    BOOL pathIsEmpty = YES;
    for (int i = 0; i < self.polyline.pointCount; i++) {
        CGPoint point = CGPointMake(self.polyline.points[i].x, self.polyline.points[i].y);
        if (pathIsEmpty) {
            CGPathMoveToPoint(path, nil, point.x, point.y);
            pathIsEmpty = NO;
        } else {
            CGPathAddLineToPoint(path, nil, point.x, point.y);
        }
    }
    self.path = path;
}