Striped Lines appear out of nowhere - ios

Question

I am trying to code a routine that would allow me to create a UIImage that is a rectangle filled with stripes on a gradient background.
My code is below and works fine for most of the cases I tried it out. Interestingly, and this is the hook, it doesn't work when I pass it 21 as height and 5 as stripedWidth.
Once I do this, the stripes appear as they should... horizontally.. but vertically they start at like (y=) -40 and end at about (y=) 4 or so. To see this better, each this image showing the effect in question:
Has anyone any idea why this is happening, or even better, what I can do against it?
-(UIImage*) stripedTextureWithStartingColor:(UIColor*) startColor withEndingColor:(UIColor*) endColor withHeight:(NSUInteger) height withStripeWidth:(NSUInteger) stripeWidth withStripeColor:(UIColor*) stripedColor {
CGSize size = CGSizeMake(2 * stripeWidth, height);
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSaveGState(context);
#try {
CGContextSetAllowsAntialiasing(context, true);
CGContextSetShouldAntialias(context, true);
NSArray* colors = [NSArray arrayWithObjects:(id) startColor.CGColor, (id) endColor.CGColor, nil];
CGFloat locations[2];
locations[0] = 0.0;
locations[1] = 1.0;
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef) colors, locations);
CGColorSpaceRelease(colorSpace);
CGContextDrawLinearGradient(context, gradient, CGPointZero, CGPointMake(0, size.height - 1), 0);
CGGradientRelease(gradient);
CGContextFillPath(context);
int lineWidth = (int) stripeWidth;
CGContextSetLineWidth(context, lineWidth / 2);
int lineCount = (float) size.height / (float) lineWidth;
lineCount -= 2;
for (int i=0; i<lineCount; i++) {
CGContextSetStrokeColorWithColor(context, stripedColor.CGColor);
float x1 = -size.height + i * 2 * lineWidth - lineWidth;
float y1 = size.height - 1 + lineWidth;
float x2 = -size.height + i * 2 * lineWidth + size.height - lineWidth;
float y2 = -lineWidth;
CGContextMoveToPoint(context, x1, y1);
CGContextAddLineToPoint(context, x2, y2);
CGContextStrokePath(context);
}
UIColor* lineTopColor = [[UIColor whiteColor] colorWithAlphaComponent:0.9];
UIColor* lineBottomColor = [[UIColor darkGrayColor] colorWithAlphaComponent:0.5];
CGContextSetStrokeColorWithColor(context, lineTopColor.CGColor);
CGContextMoveToPoint(context, 0, 0);
CGContextAddLineToPoint(context, size.width + 1, 0);
CGContextStrokePath(context);
CGContextSetStrokeColorWithColor(context, lineBottomColor.CGColor);
CGContextMoveToPoint(context, 0, size.height - 1);
CGContextAddLineToPoint(context, size.width + 1, size.height - 1);
CGContextStrokePath(context);
}
#finally {
CGContextRestoreGState(context);
}
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}

Answer 1

Found it, my algorithm was slightly incorrect with the starting of the lines