在QuartzCore中沿路径绘制文本

Question

假设我有一个点数组,形成一条线和一个文本.我怎样才能沿着这条线绘制文本

 - (void)drawRect:(CGRect)rect 

一个UIView？

我能够毫无问题地绘制路径.是否存在我忽略的标准方法或允许我沿着该路径绘制文本的框架？理想情况下,我只想使用QuartzCore/CoreGraphics来做这件事.

我尝试计算每个角色的宽度并旋转每个角色.这种作品,但我想知道是否有更优雅的方法.

Answer 1

我相信你可以在Mac OS X中做到这一点,但你最接近iPhone的是CGContextShowGlyphsWithAdvances,这甚至不会旋转.

使用循环并使用类似下面的内容绘制每个字符应该不会太难.这是根据Apple的文档改编而来的,未经过测试,因此请注意:

CGContextSelectFont(myContext, "Helvetica", 12, kCGEncodingMacRoman);
CGContextSetCharacterSpacing(myContext, 10);
CGContextSetTextDrawingMode(myContext, kCGTextFillStroke);
CGContextSetRGBFillColor(myContext, 0, 0, 0, 1);
CGContextSetRGBStrokeColor(myContext, 0, 0, 0, 1);

NSUInteger charIndex = 0;
for(NSString *myChar in arrayOfChars) {
    char *cString = [myChar UTF8String];
    CGPoint charOrigin = originForPositionAlongPath(charIndex, myPath);
    CGFloat slope = slopeForPositionAlongPath(charIndex, myPath);

    CGContextSetTextMatrix(myContext, CGAffineTransformMakeRotation(slope));
    CGContextShowTextAtPoint(myContext, charOrigin.x, charOrigin.y, cString, 1);
}

编辑:这是PositionAlongPath函数的概念.同样,他们没有经过测试,但应该接近.originAlong ...如果你的路径用完,则返回(-1,-1).

CGPoint originForPositionAlongPath(int index, NSArray *path) {
    CGFloat charWidth = 12.0;
    CGFloat widthToGo = charWidth * index;

    NSInteger i = 0;
    CGPoint position = [path objectAtIndex:i];

    while(widthToGo >= 0) {
            //out of path, return invalid point
        if(i >= [path count]) {
            return CGPointMake(-1, -1);
        }

        CGPoint next = [path objectAtIndex:i+1];

        CGFloat xDiff = next.x - position.x;
        CGFloat yDiff = next.y - position.y;
        CGFloat distToNext = sqrt(xDiff*xDiff + yDiff*yDiff);

        CGFloat fracToGo = widthToGo/distToNext
            //point is before next point in path, interpolate the answer
        if(fracToGo < 1) {
            return CGPointMake(position.x+(xDiff*fracToGo), position.y+(yDiff*fracToGo));
        }

            //advance to next point on the path
        widthToGo -= distToNext;
        position = next;
        ++i;
    }
}


CGFloat slopeForPositionAlongPath(int index, NSArray *path) {
    CGPoint begin = originForPositionAlongPath(index, path);
    CGPoint end = originForPositionAlongPath(index+1, path);

    CGFloat xDiff = end.x - begin.x;
    CGFloat yDiff = end.y - begin.y;

    return atan(yDiff/xDiff);
}