kCGTextStroke's Fill and Stroke aren't positioned correctly

问题

So I'm using the code below to apply a stroke (and fill) to text in a UILabel, and it's coming out like the image below. The stroke is heavier on one side than the other (look at the top of the letters compared to the bottom, and the right compared to the left. The period at the end makes it very noticeable, too, looks like a googly eye). I've not got any shadowing turned on at all, so I don't think it's the shadow interfering with the stroke.

What could be causing this?

- (void) drawTextInRect: (CGRect) rect
{
    CGContextRef c = UIGraphicsGetCurrentContext();
    CGContextSetTextDrawingMode(c, kCGTextFillStroke);
    CGContextSaveGState(c);
    CGContextSetRGBFillColor(c, 1.0, 0.0, 0.0, 1.0);
    CGContextSetRGBStrokeColor(c, 0.0, 1.0, 0.0, 1.0);
    [super drawTextInRect: rect];
    CGContextRestoreGState(c);
}

EDIT: So, for kicks, I took at look at the label with only the fill, and only the stroke. Turning off the stroke creates a perfectly normal-looking piece of text, as if I'd just coloured it in Interface Builder. Turning off the fill, however, shows only the stroke, which doesn't look heavier on any side than any other. **This leads me to believe that the issue is where the fill is positioned in relation to the stroke, and that neither the fill or stroke themselves are at fault. Any other thoughts on this? How can I get the fill directly centred in the stroke?

回答1:

You should probably just use kCGTextFillStroke as the drawing mode and only draw once (with separate stroke and fill colors set).

CGContextSetRGBFillColor(context, 1.0, 0.0, 0.0, 1.0);   // any color you want (this is red)
CGContextSetRGBStrokeColor(context, 0.0, 1.0, 0.0, 1.0); // any color you want (this is green)
CGContextSetTextDrawingMode(context, kCGTextFillStroke);
[self.text drawInRect:rect withFont:self.font];

Alternatively you could just stroke afterwards. Strokes are usually drawn from the center which means that half of the width is inwards and half is outwards. That would mean that if you fill after you stroke some of the stroke is going to get covered up by the fill.

回答2:

A possibility is that the overridden method translates the CTM using CGContextTranslateCTM or similar functions. The CTM is part of the state of a context and specifies a transform for all following draw calls.

You should try to save the context before the call to the overridden method and restore it afterwards:

CGContextSaveGState(c);
[super drawTextInRect: rect];
CGContextRestoreGState(c);

来源：https://stackoverflow.com/questions/15838844/kcgtextstrokes-fill-and-stroke-arent-positioned-correctly

标签

objective-c

cgcontext

core-text

quartz-core

stroke