CoreText

一、绘制流程

二、文本

- (void)drawRect:(CGRect)rect {
    CGContextRef context = UIGraphicsGetCurrentContext();
    //坐标转换
    CGAffineTransform transform = CGContextGetTextMatrix(context);
    transform = CGAffineTransformIdentity;
    CGContextTranslateCTM(context, 0, self.bounds.size.height);
    CGContextScaleCTM(context, 1.0f, -1.0f);
    
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, nil, self.bounds);

    NSAttributedString *attributeString = [[NSAttributedString alloc] initWithString:@"Hello World"];

    CTFramesetterRef frameSetterRef = CTFramesetterCreateWithAttributedString((__bridge CFAttributedStringRef)attributeString);

    CTFrameRef frameRef = CTFramesetterCreateFrame(frameSetterRef, CFRangeMake(0, attributeString.length), path, nil);

    CTFrameDraw(frameRef, context);
}

三、图片

//Core Text 不支持直接绘制图片，留出空白区域，填充上图片
-(void)drawRect:(CGRect)rect
{
    [super drawRect:rect];
    CGContextRef context = UIGraphicsGetCurrentContext();
    NSLog(@"当前context的变换矩阵 %@", NSStringFromCGAffineTransform(CGContextGetCTM(context)));
    //坐标系转换
    CGContextSetTextMatrix(context, CGAffineTransformIdentity);
    CGContextTranslateCTM(context, 0, self.bounds.size.height + 20);
    CGContextScaleCTM(context, 1.0, -1.0);
    NSLog(@"变换后context的变换矩阵 %@", NSStringFromCGAffineTransform(CGContextGetCTM(context)));
//\n终身学习，\n
    NSMutableAttributedString * attributeStr = [[NSMutableAttributedString alloc] initWithString:@"人人为师"];

    CTRunDelegateCallbacks callBacks;
    memset(&callBacks,0,sizeof(CTRunDelegateCallbacks));
    callBacks.version = kCTRunDelegateVersion1;
    callBacks.getAscent = ascentCallBacks;
    callBacks.getDescent = descentCallBacks;
    callBacks.getWidth = widthCallBacks;

    NSDictionary * dicPic = @{@"ascent":@200,@"descent":@100,@"width":@200};
    CTRunDelegateRef delegate = CTRunDelegateCreate(&callBacks, (__bridge void *)dicPic);

    NSString * placeHolderStr = @" ";
    NSMutableAttributedString * placeHolderAttrStr = [[NSMutableAttributedString alloc] initWithString:placeHolderStr];
    CFAttributedStringSetAttribute((CFMutableAttributedStringRef)placeHolderAttrStr, CFRangeMake(0, 1), kCTRunDelegateAttributeName, delegate);
    CFRelease(delegate);
    [attributeStr insertAttributedString:placeHolderAttrStr atIndex:0];

    CTFramesetterRef frameSetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attributeStr);
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, self.bounds);
    NSInteger length = attributeStr.length;
    CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, length), path, NULL);
    CTFrameDraw(frame, context);

    //图片！！！网络加载~
    UIImage * image = [UIImage imageNamed:@"1.png"];
    //坐标！。
    CGRect imgFrm = [self calculateImageRectWithFrame:frame];
    CGContextDrawImage(context,imgFrm, image.CGImage);
    CFRelease(frame);
    CFRelease(path);
    CFRelease(frameSetter);
}

//Ascent + descent = Height
static CGFloat ascentCallBacks(void * ref)
{
    return [(NSNumber *)[(__bridge NSDictionary *)ref valueForKey:@"ascent"] floatValue];
}
static CGFloat descentCallBacks(void * ref)
{
    return 100;
}

static CGFloat widthCallBacks(void * ref)
{
    return [(NSNumber *)[(__bridge NSDictionary *)ref valueForKey:@"width"] floatValue];
}

-(CGRect)calculateImageRectWithFrame:(CTFrameRef)frame
{
    NSArray * arrLines = (NSArray *)CTFrameGetLines(frame);
    NSInteger count = [arrLines count];
    CGPoint points[count];
    //拿到所有CTLine 的原点坐标
    CTFrameGetLineOrigins(frame, CFRangeMake(0, 0), points);
    for (int i = 0; i < count; i ++) {
        CTLineRef line = (__bridge CTLineRef)arrLines[i];
        NSArray * arrGlyphRun = (NSArray *)CTLineGetGlyphRuns(line);
        for (int j = 0; j < arrGlyphRun.count; j ++) {
            CTRunRef run = (__bridge CTRunRef)arrGlyphRun[j];
            NSDictionary * attributes = (NSDictionary *)CTRunGetAttributes(run);
            //取出代理
            CTRunDelegateRef delegate = (__bridge CTRunDelegateRef)[attributes valueForKey:(id)kCTRunDelegateAttributeName];
            if (delegate == nil) {
                continue;
            }
            NSDictionary * dic = CTRunDelegateGetRefCon(delegate);
            if (![dic isKindOfClass:[NSDictionary class]]) {
                continue;
            }
            //修正 UIImage 的坐标!!!
            CGPoint point = points[i];
            CGFloat ascent;
            CGFloat descent;
            CGRect boundsRun;
            boundsRun.size.width = CTRunGetTypographicBounds(run, CFRangeMake(0, 0), &ascent, &descent, NULL);
            boundsRun.size.height = ascent + descent;
            CGFloat xOffset = CTLineGetOffsetForStringIndex(line, CTRunGetStringRange(run).location, NULL);
            boundsRun.origin.x = point.x + xOffset;
            boundsRun.origin.y = point.y - descent;
            CGPathRef path = CTFrameGetPath(frame);
            CGRect colRect = CGPathGetBoundingBox(path);
            CGRect imageBounds = CGRectOffset(boundsRun, colRect.origin.x, colRect.origin.y);
            NSLog(@"%@",NSStringFromCGRect(imageBounds));
            return imageBounds;
        }
    }
    return CGRectZero;
}