CoreText 学习笔记 一

CoreText 坐标系是以左下角为坐标原点。而我们经常使用的uikit是以左上角为坐标原点，因此 CoreText 中的布局完成后需要对其进行坐标系转换

一般做法： 获取当前上下文，将当前上下文坐标转换成CT坐标系，再将布局好的CT绘制到当前上下文即可

    //获取当前上下文    CGContextRef context = UIGraphicsGetCurrentContext();    //翻转坐标系步骤    //设置当前文本矩阵    CGContextSetTextMatrix(context, CGAffineTransformIdentity);    //文本沿y轴移动    CGContextTranslateCTM(context, 0, self.bounds.size.height);    //文本翻转成为CoreText坐标系    CGContextScaleCTM(context, 1, -1);

CoreText文本布局

1.首先要确定布局时绘制的区域，其对应的类为CG(Mutable)PathRef

 2.设置文本内容，其对应的类为NS(Mutable)AttributedString

3.根据文本内容配置其CTFramesetterRef

4.利用CTFramesetterRef得到CTFrame

  //1.创建绘制区域,显示的区域可以用CGMUtablePathRef生成任意的形状    CGMutablePathRef path = CGPathCreateMutable();    CGPathAddRect(path, NULL, CGRectMake(20, 50, self.bounds.size.width - 40, self.bounds.size.height - 100));       //2.创建需要绘制的文字    NSMutableAttributedString *attString = [[NSMutableAttributedString alloc] initWithString:@"\tWhen I will learn CoreText, i think it will hard for me.But it is easy.\n\tIn fact,if you bengin learn, you can know that every thing is easy when you start.you just need some knowlages"];    //3.根据AttString生成CTFramesetterRef    CTFramesetterRef frameSetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attString);    CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, [attString length]), path, NULL);

文本属性设置

 //设置绘制的文本内容     NSMutableAttributedString *attString = [[NSMutableAttributedString alloc] initWithString:@"\tWhen I will learn CoreText, i think it will hard for me.But it is easy.\n\tIn fact,if you bengin learn, you can know that every thing is easy when you start.you just need some knowlages"];    //设置文本内容的属性    //1设置部分文字颜色    [attString addAttribute:(id)kCTForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(0 , 27)];    //2设置部分文字字体    CGFloat fontSize = 20;    CTFontRef fontRef = CTFontCreateWithName((CFStringRef)@"ArialMT", fontSize, NULL);    [attString addAttribute:(id)kCTFontAttributeName value:(__bridge id)fontRef range:NSMakeRange(0, 27)];    //3设置斜体    CTFontRef italicFontRef = CTFontCreateWithName((CFStringRef)[UIFont italicSystemFontOfSize:20].fontName, 16, NULL);    [attString addAttribute:(id)kCTFontAttributeName value:(__bridge id)italicFontRef range:NSMakeRange(27, 9)];    //4设置下划线    [attString addAttribute:(id)kCTUnderlineStyleAttributeName value:(id)[NSNumber numberWithInteger:kCTUnderlineStyleDouble] range:NSMakeRange(36, 10)];    //5设置下划线颜色    [attString addAttribute:(id)kCTUnderlineColorAttributeName value:(id)[UIColor greenColor].CGColor range:NSMakeRange(36, 10)];    //6设置空心字    long number1 = 2;    CFNumberRef numRef = CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt8Type, &number1);    [attString addAttribute:(id)kCTStrokeWidthAttributeName value:(__bridge id)numRef range:NSMakeRange(56, 10)];    //7设置字体间距    long number = 10;    CFNumberRef num = CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt8Type, &number);    [attString addAttribute:(id)kCTKernAttributeName value:(__bridge id)num range:NSMakeRange(40, 10)];    //8设置行间距    CGFloat lineSpacing = 10;    const CFIndex kNumberOfSettings = 3;    CTParagraphStyleSetting theSettings[kNumberOfSettings] = {        {kCTParagraphStyleSpecifierLineSpacingAdjustment, sizeof(CGFloat), &lineSpacing},        {kCTParagraphStyleSpecifierMaximumLineHeight, sizeof(CGFloat), &lineSpacing},        {kCTParagraphStyleSpecifierMinimumLineHeight, sizeof(CGFloat), &lineSpacing}    };    CTParagraphStyleRef theParagraphRef = CTParagraphStyleCreate(theSettings, kNumberOfSettings);    [attString addAttribute:(id)kCTParagraphStyleAttributeName value:(__bridge id)theParagraphRef range:NSMakeRange(0, [attString length])];

图片文本内容

图片宽高在工程中都需要加载后才知道，而在文本绘制中需要直接留出其位置再进行绘制，所以图片的宽高都是在数据中保存好的，此处笔者用固定值来表示其宽高。为了留出其位置我们需要用空白的字符来做占位符使用。为了知道其图片绘制的位置(即空白占位符位置)我们需要设置代理才能够得知图片绘制位置。具体步骤如下:

1.创建CTRunDelegateCallbacks 回调函数：通过回调函数来确定图片绘制的宽高
2.创建空白占位字符　　
3.设置CTRunDeleagte：通过代理来找到该字符串，并确定图片绘制的原点

#pragma mark - CTRunDelegateCallbacks Method//此处使用的字典结构来存储数值static CGFloat heightCallBack(void *ref) {    return [(NSNumber *)[(__bridge NSDictionary *)ref objectForKey:@"height"] floatValue];}static CGFloat descentCallBack (void *ref) {    return 0;}static CGFloat widthCallBack (void *ref) {    return [(NSNumber *)[(__bridge NSDictionary *)ref objectForKey:@"width"] floatValue];}

#pragma mark - 空白占位符及代理设置

 //CTRunDelegateCallBacks:用于保存指针的结构体，由CTRun delegate进行回调    CTRunDelegateCallbacks callbacks;    memset(&callbacks, 0, sizeof(CTRunDelegateCallbacks));    callbacks.version = kCTRunDelegateVersion1;    callbacks.getAscent = heightCallBack;    callbacks.getDescent = descentCallBack;    callbacks.getWidth = widthCallBack;    //图片信息字典    NSDictionary *imgInfoDic = @{@"width":@320,@"height":@230};    //创建CTRunDelegate的代理    CTRunDelegateRef delegate = CTRunDelegateCreate(&callbacks, (__bridge void*)imgInfoDic);    //使用oxFFFC作为空白占位符    unichar objectReplacementChar = 0xFFFC;    NSString *content = [NSString stringWithCharacters:&objectReplacementChar length:1];    NSMutableAttributedString *space = [[NSMutableAttributedString alloc] initWithString:content];    //设置代理 　　CFAttributedStringSetAttribute((CFMutableAttributedStringRef)space, CFRangeMake(0, 1), kCTRunDelegateAttributeName, delegate);

在贴出获取图片位置代码前，还需要补充一个理论知识，在CoreText中所有的布局都是基于行(CTLineRef)来进行的，每行都是一个CTLineRef对象，在每行当中又包含多个属性(CTRunRef)每行的属性可设置代理，如上面笔者就是对空白占位符这个CTRunRef设置了代理。下面为CTLineRef和CTRunRef的示意图

具体代码：

 //获取CTLine数组    NSArray *lines = (NSArray *)CTFrameGetLines(ctframe);    NSInteger lineCount = lines.count;    CGPoint lineOrigins[lineCount];    CTFrameGetLineOrigins(ctframe, CFRangeMake(0, 0), lineOrigins);    //遍历每一个CTline    for (NSInteger i = 0; i < lineCount; i ++) {        CTLineRef line = (__bridge CTLineRef)lines[i];        NSArray *runObjArray = (NSArray *)CTLineGetGlyphRuns(line);        //遍历每个CTLine中的CTRun找到空白字符的delegate        for (id runObj in runObjArray) {            CTRunRef run = (__bridge CTRunRef)runObj;            NSDictionary *runAttributes = (NSDictionary *)CTRunGetAttributes(run);            CTRunDelegateRef delegate = (__bridge CTRunDelegateRef)[runAttributes valueForKey:(id)kCTRunDelegateAttributeName];            if (delegate == nil) {                continue;            }            NSDictionary *metaDic = CTRunDelegateGetRefCon(delegate);            if (![metaDic isKindOfClass:[NSDictionary class]]) {                continue;            }            //找到代理后开始计算空白字符的位置            CGRect runBounds;            CGFloat ascent;            CGFloat descent;                        runBounds.size.width = CTRunGetTypographicBounds(run, CFRangeMake(0, 0), &ascent, &descent, NULL);            runBounds.size.height = ascent + descent;            //计算在行当中的x偏移量            CGFloat xOffset = CTLineGetOffsetForStringIndex(line, CTRunGetStringRange(run).location, NULL);            runBounds.origin.x = lineOrigins[i].x + xOffset;            runBounds.origin.y = lineOrigins[i].y - descent;            //获得ctframe的绘制区域            CGPathRef pathRef = CTFrameGetPath(ctframe);            //计算此绘制区域的范围            CGRect colRect = CGPathGetBoundingBox(pathRef);            //计算在此区域中空白字符的位置            CGRect delegateBounds= CGRectOffset(runBounds, colRect.origin.x, colRect.origin.y);            //记录空白字符位置            _imageRect = delegateBounds;            //返回空白字符位置            return delegateBounds;        }    }//若没有找到对应的代理则返回空位置return CGRectZero;

绘制文本内容

//绘制文本    CTFrameDraw(frame, context);    //绘制图像    UIImage *image = [UIImage imageNamed:@"boat.jpg"];    CGContextDrawImage(context, _imageRect, image.CGImage);