设置文字和图片的方法：
绘制文字的步骤是：设置NSAttributedString 或NSMutableAttributedString——> 通过attributedString 生成frameSetter ——> 生成CTFrame——>画出来
设置文字属性，重点是在NSMutableAttributedString的生成，对颜色、字体、字距进行设置。
CoreText 中并没有画图片的方法，我们同样的在NSMutableAttributedString中插入一个空字符，然后设置这个空字符占的位置和大小。把整个字符串写完以后。重点在这里：解析生成的NSAttributedString，获取到图片应该画的位置和大小，利用Core Graphics 把图片画到context中。
注释全部写在例子对应的位置上：
- (void)drawRect:(CGRect)rect
{
CGContextRef contxt = UIGraphicsGetCurrentContext();
CGContextSetTextMatrix(contxt, CGAffineTransformIdentity);
CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, self.bounds.size.height);
CGContextConcatCTM(contxt, flipVertical);
NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc]initWithString:@"1.设置字形变换矩阵为CGAffineTransformIdentity，也就是说每一个字形都不做图形变换，将当前context的坐标系进行flip，2.为图片设置CTRunDelegate,delegate决定留给图片的空间大小。 3.把图片画上去" ];
[attributedString addAttribute:NSFontAttributeName value:[UIFont systemFontOfSize:20] range:NSMakeRange(0, [attributedString length])];
[attributedString addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:NSMakeRange(0.0, 10)];
[attributedString addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(10, 20)];
//创建图片位置
NSString *taobaoImageName = @"meile.png";
CTRunDelegateCallbacks imageCallbacks;
imageCallbacks.version = kCTRunDelegateVersion1;
imageCallbacks.dealloc = RunDelegateDeallocCallback;
imageCallbacks.getAscent = RunDelegateGetAscentCallback;
imageCallbacks.getDescent = RunDelegateGetDescentCallback;
imageCallbacks.getWidth = RunDelegateGetWidthCallback;
CTRunDelegateRef runDelegate = CTRunDelegateCreate(&imageCallbacks, (__bridge voidvoid *)taobaoImageName);
NSMutableAttributedString *imageAttributedString =[[NSMutableAttributedString alloc]initWithString:@" "];//创建一个空格，来使attributedString生效
[imageAttributedString addAttribute:(NSString *)kCTRunDelegateAttributeName value:(__bridge id)runDelegate range:NSMakeRange(0, 1)];//设置回调
CFRelease(runDelegate);
[imageAttributedString addAttribute:@"imageName" value:taobaoImageName range:NSMakeRange(0, 1)];
[attributedString insertAttributedString:imageAttributedString atIndex:30];//把attribute 插入到一个特定的位置
//创建图片位置至此完成那个
CTFramesetterRef ctFrameSetter = CTFramesetterCreateWithAttributedString((CFMutableAttributedStringRef)attributedString);
CGMutablePathRef path = CGPathCreateMutable();
CGRect bounds = CGRectMake(0.0, 20.0, self.bounds.size.width, self.bounds.size.height-20);
CGPathAddRect(path, NULL, bounds);
CTFrameRef ctFrame = CTFramesetterCreateFrame(ctFrameSetter, CFRangeMake(0, 0), path, NULL);
CTFrameDraw(ctFrame, contxt);
//现在开始画图片
CFArrayRef lines = CTFrameGetLines(ctFrame);
CGPoint lineOrigins [CFArrayGetCount(lines)]; //这是一个方法
CTFrameGetLineOrigins(ctFrame, CFRangeMake(0, 0), lineOrigins);
for (int i = 0; i < CFArrayGetCount(lines); i++) {
CTLineRef line = CFArrayGetValueAtIndex(lines, i);
CGFloat lineAscent;
CGFloat lineDescent;
CGFloat lineLeading;
CTLineGetTypographicBounds(line, &lineAscent, &lineDescent, &lineLeading);
CFArrayRef runs = CTLineGetGlyphRuns(line);
for (int j = 0; j < CFArrayGetCount(runs); j++) {
CGFloat runAscent;
CGFloat runDescent;
CGPoint lineOrigin = lineOrigins[i];
CTRunRef run = CFArrayGetValueAtIndex(runs, j);
NSDictionary* attributes = (NSDictionary*)CTRunGetAttributes(run);
CGRect runRect;
runRect.size.width = CTRunGetTypographicBounds(run, CFRangeMake(0,0), &runAscent, &runDescent, NULL);
runRect=CGRectMake(lineOrigin.x + CTLineGetOffsetForStringIndex(line, CTRunGetStringRange(run).location, NULL), lineOrigin.y - runDescent, runRect.size.width, runAscent + runDescent);
NSString *imageName = [attributes objectForKey:@"imageName"];
//图片渲染逻辑
if (imageName)
{
UIImage *image = [UIImage imageNamed:imageName];
if (image)
{
CGRect imageDrawRect;
imageDrawRect.size = image.size;
imageDrawRect.origin.x = runRect.origin.x + lineOrigin.x;
imageDrawRect.origin.y = lineOrigin.y +lineDescent+10;// 怎么精确计算
CGContextDrawImage(contxt, imageDrawRect, image.CGImage);
}
}
}
}
//画图片结束
CFRelease(ctFrame);
CFRelease(path);
CFRelease(ctFrameSetter);
}