Drawing a polygon with one color for stroke, and a

问题:

I'm having trouble with drawing some lines that are stroked with a color and then filling their insides (they make a polygon) with another one.

UIColor *houseBorderColor = [UIColor colorWithRed:(170/255.0) green:(138/255.0) blue:(99/255.0) alpha:1];
CGContextSetStrokeColorWithColor(context, houseBorderColor.CGColor);
CGContextSetLineWidth(context, 3);

// Draw the polygon
CGContextMoveToPoint(context, 20, viewHeight-19.5);
CGContextAddLineToPoint(context, 200, viewHeight-19.5); // base
CGContextAddLineToPoint(context, 300, viewHeight-119.5); // right border
CGContextAddLineToPoint(context, 120, viewHeight-119.5);
CGContextAddLineToPoint(context, 20, viewHeight-19.5);

// Fill it
CGContextSetRGBFillColor(context, (248/255.0), (222/255.0), (173/255.0), 1);
//CGContextFillPath(context);

// Stroke it
CGContextStrokePath(context);

With the CGContextStrokePath commented out, I get this result:

But if I uncomment CGContextStrokePath and fill out the polygon, the color overflows the strokes:

How do you achieve a result like this (without having to redo the whole drawing procedure twice):

回答1:

You can use

CGContextDrawPath(context, kCGPathFillStroke);

instead of

CGContextFillPath(context);
CGContextStrokePath(context);

The problem is that both CGContextFillPath() and CGContextStrokePath(context) clear the current path, so that only the first operation succeeds, and the second operation draws nothing. CGContextDrawPath() combines fill and stroke without clearing the path in between.

回答2:

Using UIBezierPath you could do this:

UIBezierPath *path = [[UIBezierPath alloc] init];
[path moveToPoint:CGPointMake(20, viewHeight-19.5)];
[path addLineToPoint:CGPointMake(200, viewHeight-19.5)];
[path addLineToPoint:CGPointMake(300, viewHeight-119.5)];
[path addLineToPoint:CGPointMake(120, viewHeight-119.5)];
[path addLineToPoint:CGPointMake(20, viewHeight-19.5)];

[[UIColor colorWithRed:(248/255.0) green:(222/255.0) blue:(173/255.0) alpha:1.0] setFill];
[path fill];
[[UIColor colorWithRed:(170/255.0) green:(138/255.0) blue:(99/255.0) alpha:1.0] setStroke];
[path stroke];

回答3:

When you stroke or fill the path in the context, the context removes the path for you (it expects that it's work is done). You must add the path again if you want to fill it after stroking it.

It's probably best to create a CGPathRef path local variable, build the path, add it, stroke, add it again, fill.

CGMutablePathRef path = CGPathCreateMutable();
CGPathMoveToPoint(path, nil, 20, viewHeight-19.5);
CGPathAddLineToPoint(path nil, 200, viewHeight-19.5); // base
CGPathAddLineToPoint(path nil, 300, viewHeight-119.5); // right border
CGPathAddLineToPoint(path nil, 120, viewHeight-119.5);
CGPathAddLineToPoint(path nil, 20, viewHeight-19.5);

CGContextAddPath(context, path);
CGContextFillPath(context);

// possibly modify the path here if you need to

CGContextAddPath(context, path);
CGContextStrokePath(context);