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一、字符(Character)和字形(Glyphs)

排版过程中一个重要的步骤就是从字符到字形的转换，字符表示信息本身，而字形是它的图形表现形式。字符一般就是指某种编码，如Unicode编码，而字形则是这些编码对应的图片。但是他们之间不是一一对应关系，同个字符的不同字体族，不同字体大小，不同字体样式都对应了不同的字形。而由于连写(Ligatures)的存在，多个字符也会存在对应一个字形的情况。

下面就来详情看看字形的各个参数也就是所谓的字形度量Glyph Metrics

（1）、边界框 bbox(bounding box)

这是一个假想的框子，它尽可能紧密的装入字形。 （2）、基线(baseline) 一条假想的线,一行上的字形都以此线作为上下位置的参考，在这条线的左侧存在一个点叫做基线的原点， （3）、上行高度(ascent) 从原点到字体中最高（这里的高深都是以基线为参照线的）的字形的顶部的距离，ascent是一个正值 （4）、下行高度(descent) 从原点到字体中最深的字形底部的距离，descent是一个负值（比如一个字体原点到最深的字形的底部的距离为2，那么descent就为-2） （5）、行距(line gap) line gap也可以称作leading（其实准确点讲应该叫做External leading）,行高line Height则可以通过 ascent + |descent| + linegap 来计算。 （6）、字间距(Kerning) 字与字之间的距离，为了排版的美观，并不是所有的字形之间的距离都是一致的，但是这个基本步影响到我们的文字排版。 （7）、基础原点(Origin) 基线上最左侧的点。

红框高度既为当前行的行高，绿线为baseline，绿色到红框上部分为当前行的最大Ascent，绿线到黄线为当前行的最大Desent，而黄框的高即为行间距。由此可以得出：lineHeight = Ascent + |Decent| + Leading。

二、坐标系

传统的Mac中的坐标系的原点在左下角，比如NSView默认的坐标系，原点就在左下角。但Mac中有些View为了其实现的便捷将原点变换到左上角，像NSTableView的坐标系坐标原点就在左上角。

iOS UIKit中，UIView是以左上角为原点，而Core Text一开始的定位是使用与桌面应用的排版系统，桌面应用的坐标系是以左下角为原点，即Core Text在绘制的时候也是参照左下角为原点进行绘制的，所以需要对当前的坐标系进行处理。

实际上，Core Graphic 中的context也是以左下角为原点的， 但是为什么我们用Core Graphic 绘制一些简单的图形的时候不需要对坐标系进行处理呢，是因为通过这个方法UIGraphicsGetCurrentContext()来获得的当前context是已经被处理过的了，用下面方法可以查看指定的上下文的当前图形状态变换矩阵。

• 方法一

//因为Core Text要配合Core Graphic 配合使用的，如Core Graphic一样，绘图的时候需要获得当前的上下文进行绘制CGContextRef context = UIGraphicsGetCurrentContext();NSLog(@"当前context的变换矩阵 %@", NSStringFromCGAffineTransform(CGContextGetCTM(context)));//翻转当前的坐标系（因为对于底层绘制引擎来说，屏幕左下角为（0，0））CGContextSetTextMatrix(context, CGAffineTransformIdentity);//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CGAffineTransform flipVertical = CGAffineTransformMake(1,0,0,-1,0,self.bounds.size.height);CGContextConcatCTM(context, flipVertical);//将当前context的坐标系进行flipNSLog(@"翻转后context的变换矩阵 %@", NSStringFromCGAffineTransform(CGContextGetCTM(context)));

打印结果为：

当前context的变换矩阵 [2, 0, 0, -2, 0, 800]翻转后context的变换矩阵 [2, 0, 0, 2, 0, 0]

• 方法二

//因为Core Text要配合Core Graphic 配合使用的，如Core Graphic一样，绘图的时候需要获得当前的上下文进行绘制CGContextRef context = UIGraphicsGetCurrentContext();NSLog(@"当前context的变换矩阵 %@", NSStringFromCGAffineTransform(CGContextGetCTM(context)));//翻转当前的坐标系（因为对于底层绘制引擎来说，屏幕左下角为（0，0））CGContextSetTextMatrix(context, CGAffineTransformIdentity);CGContextTranslateCTM(context, 0, self.bounds.size.height);CGContextScaleCTM(context, 1.0, -1.0);NSLog(@"翻转后context的变换矩阵 %@", NSStringFromCGAffineTransform(CGContextGetCTM(context)));

打印：

当前context的变换矩阵 [2, 0, 0, -2, 0, 800]翻转后context的变换矩阵 [2, 0, -0, 2, 0, 0]

可以发现变换矩阵与CGAffineTransformIdentity的值[1, 0, 0, 1, 0, 0]是不相同的，并且与设备是否为Retina屏和设备尺寸相关。他的作用是将上下文空间坐标系进行翻转，并使原来的左下角原点变成左上角是原点，并将向上为正y轴变为向下为正y轴。 所以在使用drawRect的时候，当前的context已经被做了一次翻转，如果不对当前的坐标系进行处理，会发现，绘制出来的文字是镜像上下颠倒的。所以在UIView的drawRect方法中的context上进行Core Text绘制之前需要对context进行一次Flip。

三、主要函数

1、传入CTFrame，返回一个装有多个CTLine对象的数组。

CFArrayRef CTFrameGetLines(        CTFrameRef frame ) CT_AVAILABLE(10_5, 3_2);

2、获取数组中的元素个数

CFIndex CFArrayGetCount(CFArrayRef theArray);

3、获取数组中第idx个元素

const void *CFArrayGetValueAtIndex(CFArrayRef theArray, CFIndex idx);

4、 获取所有CTLineRef的基础原点，传入CTFrame，CFRange，和一个CGPoint的结构体数组指针，该函数会把每一个CTLine的origin坐标写到数组里。

void CTFrameGetLineOrigins(        CTFrameRef frame,        CFRange range,        CGPoint origins[] ) CT_AVAILABLE(10_5, 3_2);

5、获取CTLine中文字在整段文字中的Range

CFRange CTLineGetStringRange(    CTLineRef line ) CT_AVAILABLE(10_5, 3_2);

6、获取CTLine中的CTRun的数组

CFArrayRef CTLineGetGlyphRuns(    CTLineRef line ) CT_AVAILABLE(10_5, 3_2);

7、获取CTRun在整段文字中的Range

CFRange CTRunGetStringRange(    CTRunRef run ) CT_AVAILABLE(10_5, 3_2);

8、 获取点击处position文字在整段文字中的index

CFIndex CTLineGetStringIndexForPosition(    CTLineRef line,    CGPoint position ) CT_AVAILABLE(10_5, 3_2);

9、获取整段文字中charIndex位置的字符相对line的原点的x值

CGFloat CTLineGetOffsetForStringIndex(    CTLineRef line,    CFIndex charIndex,    CGFloat * __nullable secondaryOffset ) CT_AVAILABLE(10_5, 3_2);

10、获取数组中字形个个数

CFIndex CTLineGetGlyphCount(    CTLineRef line ) CT_AVAILABLE(10_5, 3_2);

11、设置CoreText绘制前的坐标。设置基线位置

CG_EXTERN void CGContextSetTextPosition(CGContextRef __nullable c,    CGFloat x, CGFloat y)    CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

12、绘制CTLine。

void CTLineDraw(    CTLineRef line,    CGContextRef context ) CT_AVAILABLE(10_5, 3_2);

13、获取CTLine的上行高度，下行高度，行距

double CTLineGetTypographicBounds(    CTLineRef line,    CGFloat * __nullable ascent,    CGFloat * __nullable descent,    CGFloat * __nullable leading ) CT_AVAILABLE(10_5, 3_2);

14、设置当前文本矩阵

CG_EXTERN void CGContextSetTextMatrix(CGContextRef __nullable c,    CGAffineTransform t)    CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

15、获取一行文字的范围， 就是指把这一行文字点有的像素矩阵作为一个image图片，来得到整个矩形区域。相对于每一行基线原点的偏移量和宽高（例如：{

{1.2， -2.57227}, {208.025, 19.2523}}，就是相对于本身的基线原点向右偏移1.2个单位，向下偏移2.57227个单位，后面是宽高）

CGRect CTLineGetImageBounds(    CTLineRef line,    CGContextRef __nullable context ) CT_AVAILABLE(10_5, 3_2);

例如：

//获取frame中CTLineRef数组CFArrayRef Lines = CTFrameGetLines(frame);//获取数组Lines中的个数CFIndex lineCount = CFArrayGetCount(Lines);//获取数组中第一个CTLineRefCTLineRef lineRef = CFArrayGetValueAtIndex(Lines, 0);//获取lineRef中CTRunRef数组CFArrayRef runs = CTLineGetGlyphRuns(lineRef);//获取CTLineRef中字形个数CFIndex rus = CTLineGetGlyphCount(lineRef);//获取数组runs中的个数CFIndex runCount = CFArrayGetCount(runs);NSLog(@"lines = %ld   runs = %ld rus = %ld",lineCount,runCount,rus);

打印：

lines = 7   runs = 5 rus = 37

四、举例

1、绘框

- (void)drawRect:(CGRect)rect{    // 步骤1：得到当前用于绘制画布的上下文，用于后续将内容绘制在画布上    // 因为Core Text要配合Core Graphic 配合使用的，如Core Graphic一样，绘图的时候需要获得当前的上下文进行绘制    CGContextRef context = UIGraphicsGetCurrentContext();    NSLog(@"当前context的变换矩阵 %@", NSStringFromCGAffineTransform(CGContextGetCTM(context)));    // 步骤2：翻转当前的坐标系（因为对于底层绘制引擎来说，屏幕左下角为（0，0））    CGContextSetTextMatrix(context, CGAffineTransformIdentity);//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    CGAffineTransform flipVertical = CGAffineTransformMake(1,0,0,-1,0,self.bounds.size.height);    CGContextConcatCTM(context, flipVertical);//将当前context的坐标系进行flip    NSLog(@"翻转后context的变换矩阵 %@", NSStringFromCGAffineTransform(CGContextGetCTM(context)));    // 步骤3：创建绘制区域    CGMutablePathRef path = CGPathCreateMutable();    CGPathAddRect(path, NULL, self.bounds);    // 步骤4：创建需要绘制的文字与计算需要绘制的区域    NSMutableAttributedString *attrString = [[NSMutableAttributedString alloc] initWithString:@"iOS程序在启动时会创建一个主线程，而在一个线程只能执行一件事情，如果在主线程执行某些耗时操作，例如加载网络图片，下载资源文件等会阻塞主线程（导致界面卡死，无法交互），所以就需要使用多线程技术来避免这类情况。iOS中有三种多线程技术 NSThread，NSOperation，GCD，这三种技术是随着IOS发展引入的，抽象层次由低到高，使用也越来越简单。"];    // 步骤5：根据AttributedString生成CTFramesetterRef    CTFramesetterRef frameSetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attrString);    CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, [attrString length]), path, NULL);    //获取frame中CTLineRef数组    CFArrayRef Lines = CTFrameGetLines(frame);    //获取数组Lines中的个数    CFIndex lineCount = CFArrayGetCount(Lines);    //获取基线原点    CGPoint origins[lineCount];    CTFrameGetLineOrigins(frame, CFRangeMake(0, 0), origins);    for (CFIndex i = 0; i < lineCount; i ++) {        CTLineRef line = CFArrayGetValueAtIndex(Lines, i);        //相对于每一行基线原点的偏移量和宽高（例如：{   {1.2， -2.57227}, {208.025, 19.2523}}，就是相对于本身的基线原点向右偏移1.2个单位，向下偏移2.57227个单位，后面是宽高）        CGRect lineBounds = CTLineGetImageBounds((CTLineRef)line, context);        NSLog(@"lineBounds = %@",NSStringFromCGRect(lineBounds));        NSLog(@"point = %@",NSStringFromCGPoint(origins[i]));        //每一行的起始点（相对于context）加上相对于本身基线原点的偏移量        lineBounds.origin.x += origins[i].x;        lineBounds.origin.y += origins[i].y;        //填充        CGContextSetLineWidth(context, 1.0);        CGContextAddRect(context,lineBounds);        CGContextSetStrokeColorWithColor(context, [[UIColor redColor] CGColor]);        CGContextStrokeRect(context, lineBounds);    }    // 步骤6：进行绘制    CTFrameDraw(frame, context);    // 步骤7.内存管理    CFRelease(frame);    CFRelease(path);    CFRelease(frameSetter);}

打印：

当前context的变换矩阵 [2, 0, 0, -2, 0, 800]翻转后context的变换矩阵 [2, 0, 0, 2, 0, 0]lineBounds = {   {0.7734375, -2.052}, {354.70246875000004, 11.964}}point = {    0, 387}lineBounds = {   {0.44400000000000001, -2.052}, {371.06400000000002, 11.94}}point = {    0, 370}lineBounds = {   {0.38400000000000001, -2.052}, {371.06400000000002, 11.975999999999999}}point = {    0, 353}lineBounds = {   {0.41999999999999998, -2.052}, {320.66929687499999, 11.927999999999999}}point = {    0, 336}lineBounds = {   {0.9140625, -2.501953125}, {366.28096875, 12.473953125}}point = {    0, 319}lineBounds = {   {0.40800000000000003, -2.052}, {148.16400000000002, 11.94}}point = {    0, 302}

2、单行绘制

- (void)drawRect:(CGRect)rect{    // 步骤1：得到当前用于绘制画布的上下文，用于后续将内容绘制在画布上    // 因为Core Text要配合Core Graphic 配合使用的，如Core Graphic一样，绘图的时候需要获得当前的上下文进行绘制    CGContextRef context = UIGraphicsGetCurrentContext();    NSLog(@"当前context的变换矩阵 %@", NSStringFromCGAffineTransform(CGContextGetCTM(context)));    // 步骤2：翻转当前的坐标系（因为对于底层绘制引擎来说，屏幕左下角为（0，0））    CGContextSetTextMatrix(context, CGAffineTransformIdentity);//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    CGAffineTransform flipVertical = CGAffineTransformMake(1,0,0,-1,0,self.bounds.size.height);    CGContextConcatCTM(context, flipVertical);//将当前context的坐标系进行flip    NSLog(@"翻转后context的变换矩阵 %@", NSStringFromCGAffineTransform(CGContextGetCTM(context)));    // 步骤3：创建绘制区域    CGMutablePathRef path = CGPathCreateMutable();    CGPathAddRect(path, NULL, self.bounds);    // 步骤4：创建需要绘制的文字与计算需要绘制的区域    NSMutableAttributedString *attrString = [[NSMutableAttributedString alloc] initWithString:@"门梁真可怕 当中英文混合之后，����������会出现行高不统一的情况，现在在绘制的时候根据字体的descender来偏移绘制，对齐baseline。����������同时点击链接的时候会调用drawRect: 造成绘制异常，所以将setNeedsDisplay注释，如需刷新，请手动调用。带上emoji以供测试��������������������"];    CTFontRef font = CTFontCreateWithName(CFSTR("Georgia"), 20, NULL);    [attrString addAttribute:(id)kCTFontAttributeName value:(__bridge id)font range:NSMakeRange(0, attrString.length)];    // 步骤5：根据AttributedString生成CTFramesetterRef    CTFramesetterRef frameSetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attrString);    CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, [attrString length]), path, NULL);    //获取frame中CTLineRef数组    CFArrayRef Lines = CTFrameGetLines(frame);    //获取数组Lines中的个数    CFIndex lineCount = CFArrayGetCount(Lines);    //获取基线原点    CGPoint origins[lineCount];    CTFrameGetLineOrigins(frame, CFRangeMake(0, 0), origins);    for (CFIndex i = 0; i < lineCount; i ++) {        CTLineRef line = CFArrayGetValueAtIndex(Lines, i);         //遍历每一行CTLine        CGFloat lineAscent;        CGFloat lineDescent;        CGFloat lineLeading; // 行距        // 该函数除了会设置好ascent,descent,leading之外，还会返回这行的宽度        CTLineGetTypographicBounds(line, &lineAscent, &lineDescent, &lineLeading);        NSLog(@"lineAscent = %f",lineAscent);        NSLog(@"lineDescent = %f",lineDescent);        NSLog(@"lineLeading = %f",lineLeading);        CGPoint lineOrigin = origins[i];        NSLog(@"point = %@",NSStringFromCGPoint(lineOrigin));        CGRect oldLineBounds = CTLineGetImageBounds((CTLineRef)line, context);        NSLog(@"lineBounds改动前：%@",NSStringFromCGRect(oldLineBounds));        NSLog(@"y = %f  d = %f  fontD = %f",lineOrigin.y,lineDescent,CTFontGetDescent(font));        NSLog(@"Position修改前%@",NSStringFromCGPoint(CGContextGetTextPosition(context)));        CGContextSetTextPosition(context, lineOrigin.x, lineOrigin.y -lineDescent - CTFontGetDescent(font));        NSLog(@"Position修改后%@",NSStringFromCGPoint(CGContextGetTextPosition(context)));        CGRect lineBounds = CTLineGetImageBounds((CTLineRef)line, context);        NSLog(@"lineBounds改动后 = %@",NSStringFromCGRect(lineBounds));        //填充        CGContextSetLineWidth(context, 1.0);        CGContextAddRect(context,lineBounds);        CGContextSetStrokeColorWithColor(context, [[UIColor redColor] CGColor]);        CGContextStrokeRect(context, lineBounds);        CTLineDraw(line, context);//绘制原点为左下角    }    // 步骤6：进行绘制//    CTFrameDraw(frame, context);    // 步骤7.内存管理    CFRelease(frame);    CFRelease(path);    CFRelease(frameSetter);}

打印数据：

当前context的变换矩阵 [2, 0, 0, -2, 0, 800]翻转后context的变换矩阵 [2, 0, 0, 2, 0, 0]lineAscent = 22.000000lineDescent = 6.875000lineLeading = 0.000000point = {0, 378}lineBounds改动前：{   {1.98, -3.5499999999999998}, {328.34421874999998, 22}}y = 378.000000  d = 6.875000  fontD = 4.384766Position修改前{0, 0}Position修改后{0, 366.740234375}lineBounds改动后 = {   {1.98, 363.19023437499999}, {328.34421874999998, 22}}lineAscent = 22.000000lineDescent = 6.875000lineLeading = 0.000000point = {0, 349}lineBounds改动前：{   {331.32421875, 363.19023437499999}, {367.41999999999996, 22}}y = 349.000000  d = 6.875000  fontD = 4.384766Position修改前{330.82421875, 366.740234375}Position修改后{0, 337.740234375}lineBounds改动后 = {   {0.5, 334.19023437499999}, {367.41999999999996, 22}}lineAscent = 21.200000lineDescent = 6.800000lineLeading = 0.000000point = {0, 321}lineBounds改动前：{   {369.83999999999997, 335.58023437499997}, {368.16703124999998, 18.66}}y = 321.000000  d = 6.800000  fontD = 4.384766Position修改前{369, 337.740234375}Position修改后{0, 309.81523437499999}lineBounds改动后 = {   {0.83999999999999997, 307.65523437499996}, {368.16703124999998, 18.66}}lineAscent = 22.000000lineDescent = 6.875000lineLeading = 0.000000point = {0, 292}lineBounds改动前：{   {370.40703124999999, 306.26523437499998}, {365.81625000000003, 22}}y = 292.000000  d = 6.875000  fontD = 4.384766Position修改前{369.70703125, 309.81523437499999}Position修改后{0, 280.740234375}lineBounds改动后 = {   {0.70000000000000007, 277.19023437499999}, {365.81625000000003, 22}}lineAscent = 21.200000lineDescent = 6.800000lineLeading = 0.000000point = {0, 264}lineBounds改动前：{   {368.41624999999999, 278.58023437499997}, {353.68367187500002, 18.620000000000001}}y = 264.000000  d = 6.800000  fontD = 4.384766Position修改前{367.65625, 280.740234375}Position修改后{0, 252.81523437499999}lineBounds改动后 = {   {0.76000000000000001, 250.65523437499999}, {353.68367187500002, 18.620000000000001}}lineAscent = 21.200000lineDescent = 6.800000lineLeading = 0.000000point = {0, 236}lineBounds改动前：{   {356.94367187500001, 248.47929687499999}, {363.27226562499999, 20.775937499999998}}y = 236.000000  d = 6.800000  fontD = 4.384766Position修改前{355.263671875, 252.81523437499999}Position修改后{0, 224.81523437499999}lineBounds改动后 = {   {1.6799999999999999, 220.47929687499999}, {363.27226562499999, 20.775937499999998}}lineAscent = 21.200000lineDescent = 6.800000lineLeading = 0.000000point = {0, 208}lineBounds改动前：{   {367.25226562500001, 220.47929687499999}, {328.44562499999995, 20.915937499999998}}y = 208.000000  d = 6.800000  fontD = 4.384766Position修改前{366.572265625, 224.81523437499999}Position修改后{0, 196.81523437499999}lineBounds改动后 = {   {0.68000000000000005, 192.47929687499999}, {328.44562499999995, 20.915937499999998}}lineAscent = 22.000000lineDescent = 6.875000lineLeading = 0.000000point = {0, 179}lineBounds改动前：{   {330.265625, 193.26523437499998}, {229, 22}}y = 179.000000  d = 6.875000  fontD = 4.384766Position修改前{329.765625, 196.81523437499999}Position修改后{0, 167.740234375}lineBounds改动后 = {   {0.5, 164.19023437499999}, {229, 22}}

3、固定行间距

行高=每行的asent + 每行的descent + 行数*行间距

.m

#import "MyView.h"#import 
   
    // 行距const CGFloat kGlobalLineLeading = 5.0;@interface MyView()@property (nonatomic ,assign) CGFloat textHeight;@end@implementation MyView- (instancetype)initWithFrame:(CGRect)frame{    self = [super initWithFrame:frame];    if (self) {        self.text = @"我自横刀向天笑，去留肝胆两昆仑。--谭嗣同同学你好啊。This is my first CoreText demo,how are you ?I love three things,the sun,the moon,and you.the sun for the day,the moon for the night,and you forever.��������������去年今日此门中，人面桃花相映红。人面不知何处去，桃花依旧笑春风。��������������少年不知愁滋味，爱上层楼，爱上层楼，为赋新词强说愁。56321363464.而今识尽愁滋味，欲说还休，欲说还休，却道天凉好个秋。123456，7890，56321267895434。缺月挂疏桐，漏断人初静。谁见幽人独往来，缥缈孤鸿影。惊起却回头，有恨无人省。捡尽寒枝不肯栖，寂寞沙洲冷。";        self.font = [UIFont systemFontOfSize:15];    }    return self;}#pragma mark - 计算高度/** *  高度 = 每行的asent + 每行的descent + 行数*行间距 *  行间距为指定的数值 */+ (CGFloat)textHeightWithText:(NSString *)aText width:(CGFloat)aWidth font:(UIFont *)aFont{    NSMutableAttributedString *content = [[NSMutableAttributedString alloc] initWithString:aText];    // 设置全局样式    [self addGlobalAttributeWithContent:content font:aFont];    CTFramesetterRef framesetterRef = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)content);    //粗略的计算高度    CGSize suggestSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetterRef, CFRangeMake(0, aText.length), NULL, CGSizeMake(aWidth, MAXFLOAT), NULL);    CGMutablePathRef path = CGPathCreateMutable();    CGPathAddRect(path, NULL, CGRectMake(0, 0, aWidth, suggestSize.height*10)); // 10这个数值是随便给的，主要是为了确保高度足够    CTFrameRef frameRef = CTFramesetterCreateFrame(framesetterRef, CFRangeMake(0, aText.length), path, NULL);    CFArrayRef lines = CTFrameGetLines(frameRef);    CFIndex lineCount = CFArrayGetCount(lines);    CGFloat ascent = 0;    CGFloat descent = 0;    CGFloat leading = 0;    CGFloat totalHeight = 0;    NSLog(@"计算高度开始");    for (CFIndex i = 0; i < lineCount; i++){        CTLineRef lineRef = CFArrayGetValueAtIndex(lines, i);        CTLineGetTypographicBounds(lineRef, &ascent, &descent, &leading);        NSLog(@"ascent = %f---descent = %f---leading = %f",ascent,descent,leading);        totalHeight += ascent + descent + kGlobalLineLeading;//行间距    }    NSLog(@"totalHeight = %f",totalHeight);    return totalHeight;}#pragma mark - 工具方法#pragma mark 给字符串添加全局属性，比如行距，字体大小，默认颜色+ (void)addGlobalAttributeWithContent:(NSMutableAttributedString *)aContent font:(UIFont *)aFont{    CGFloat lineLeading = kGlobalLineLeading; // 行间距    const CFIndex kNumberOfSettings = 2;    //设置段落格式    CTParagraphStyleSetting lineBreakStyle;    CTLineBreakMode lineBreakMode = kCTLineBreakByWordWrapping;    lineBreakStyle.spec = kCTParagraphStyleSpecifierLineBreakMode;    lineBreakStyle.valueSize = sizeof(CTLineBreakMode);    lineBreakStyle.value = &lineBreakMode;    //设置行距    CTParagraphStyleSetting lineSpaceStyle;    CTParagraphStyleSpecifier spec;    spec = kCTParagraphStyleSpecifierLineSpacingAdjustment;    lineSpaceStyle.spec = spec;    lineSpaceStyle.valueSize = sizeof(CGFloat);    lineSpaceStyle.value = &lineLeading;    // 结构体数组    CTParagraphStyleSetting theSettings[kNumberOfSettings] = {        lineBreakStyle,        lineSpaceStyle,    };    CTParagraphStyleRef theParagraphRef = CTParagraphStyleCreate(theSettings, kNumberOfSettings);    // 将设置的行距应用于整段文字    [aContent addAttribute:NSParagraphStyleAttributeName value:(__bridge id)(theParagraphRef) range:NSMakeRange(0, aContent.length)];    CFStringRef fontName = (__bridge CFStringRef)aFont.fontName;    CTFontRef fontRef = CTFontCreateWithName(fontName, aFont.pointSize, NULL);    // 将字体大小应用于整段文字    [aContent addAttribute:NSFontAttributeName value:(__bridge id)fontRef range:NSMakeRange(0, aContent.length)];    // 给整段文字添加默认颜色    [aContent addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(0, aContent.length)];    // 内存管理    CFRelease(theParagraphRef);    CFRelease(fontRef);}/** *  一行一行绘制，未调整行高（行高不固定） */- (void)drawRectWithLineByLine{    // 1.创建需要绘制的文字    NSMutableAttributedString *attributed = [[NSMutableAttributedString alloc] initWithString:self.text];    // 2.设置行距等样式    [[self class] addGlobalAttributeWithContent:attributed font:self.font];    self.textHeight = [[self class] textHeightWithText:self.text width:CGRectGetWidth(self.bounds) font:self.font];    // 3.创建绘制区域，path的高度对绘制有直接影响，如果高度不够，则计算出来的CTLine的数量会少一行或者少多行    CGMutablePathRef path = CGPathCreateMutable();    CGPathAddRect(path, NULL, CGRectMake(0, 0, CGRectGetWidth(self.bounds), self.textHeight));    // 4.根据NSAttributedString生成CTFramesetterRef    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attributed);    CTFrameRef ctFrame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, attributed.length), path, NULL);    // 1.获取上下文    CGContextRef contextRef = UIGraphicsGetCurrentContext();    // 2.转换坐标系    CGContextSetTextMatrix(contextRef, CGAffineTransformIdentity);    CGContextTranslateCTM(contextRef, 0, self.textHeight); // 此处用计算出来的高度    CGContextScaleCTM(contextRef, 1.0, -1.0);    // 重置高度    //    CGPathAddRect(path, NULL, CGRectMake(0, 0, CGRectGetWidth(self.bounds), self.textHeight));    // 一行一行绘制    CFArrayRef lines = CTFrameGetLines(ctFrame);    CFIndex lineCount = CFArrayGetCount(lines);    CGPoint lineOrigins[lineCount];    // 把ctFrame里每一行的初始坐标写到数组里，注意CoreText的坐标是左下角为原点    CTFrameGetLineOrigins(ctFrame, CFRangeMake(0, 0), lineOrigins);    for (int i = 0; i < lineCount; i++){        CGPoint point = lineOrigins[i];        NSLog(@"point.y = %f",point.y);    }    NSLog(@"font.ascender = %f,descender = %f,lineHeight = %f,leading = %f",self.font.ascender,self.font.descender,self.font.lineHeight,self.font.leading);    CGFloat frameY = 0;    for (CFIndex i = 0; i < lineCount; i++){        // 遍历每一行CTLine        CTLineRef line = CFArrayGetValueAtIndex(lines, i);        CGFloat lineAscent;        CGFloat lineDescent;        CGFloat lineLeading; // 行距        // 该函数除了会设置好ascent,descent,leading之外，还会返回这行的宽度        CTLineGetTypographicBounds(line, &lineAscent, &lineDescent, &lineLeading);        NSLog(@"lineAscent = %f",lineAscent);        NSLog(@"lineDescent = %f",lineDescent);        NSLog(@"lineLeading = %f",lineLeading);        CGPoint lineOrigin = lineOrigins[i];        NSLog(@"i = %ld, lineOrigin = %@",i,NSStringFromCGPoint(lineOrigin));        // 微调Y值，需要注意的是CoreText的Y值是在baseLine处，而不是下方的descent。        // lineDescent为正数，self.font.descender为负数        if (i > 0){            // 第二行之后需要计算            frameY = frameY - kGlobalLineLeading - lineAscent;            lineOrigin.y = frameY;        }else{            // 第一行可直接用            frameY = lineOrigin.y;        }        // 调整坐标        CGContextSetTextPosition(contextRef, lineOrigin.x, lineOrigin.y);        CTLineDraw(line, contextRef);        // 微调        frameY = frameY - lineDescent;    }    CFRelease(path);    CFRelease(framesetter);    CFRelease(ctFrame);}- (void)drawRect:(CGRect)rect{    [self drawRectWithLineByLine];}@end
   

.h文件

#import 
   
    @interface MyView : UIView@property (nonatomic ,copy) NSString *text;@property (nonatomic ,strong) UIFont *font;+ (CGFloat)textHeightWithText:(NSString *)aText width:(CGFloat)aWidth font:(UIFont *)aFont;@end
   

结果：

3、固定行高

总高度 = 行数*每行的高度

.m

#import "MyView.h"#import 
   
    // 行距const CGFloat kGlobalLineLeading = 5.0;// 在15字体下，比值小于这个计算出来的高度会导致emoji显示不全const CGFloat kPerLineRatio = 1.4;@interface MyView()@property (nonatomic ,assign) CGFloat textHeight;@end@implementation MyView- (instancetype)initWithFrame:(CGRect)frame{    self = [super initWithFrame:frame];    if (self) {        self.text = @"我自横刀向天笑，去留肝胆两昆仑。--谭嗣同同学你好啊。This is my first CoreText demo,how are you ?I love three things,the sun,the moon,and you.the sun for the day,the moon for the night,and you forever.��������������去年今日此门中，人面桃花相映红。人面不知何处去，桃花依旧笑春风。��������������少年不知愁滋味，爱上层楼，爱上层楼，为赋新词强说愁。56321363464.而今识尽愁滋味，欲说还休，欲说还休，却道天凉好个秋。123456，7890，56321267895434。缺月挂疏桐，漏断人初静。谁见幽人独往来，缥缈孤鸿影。惊起却回头，有恨无人省。捡尽寒枝不肯栖，寂寞沙洲冷。";        self.font = [UIFont systemFontOfSize:15];    }    return self;}/** *  高度 = 每行的固定高度 * 行数 */+ (CGFloat)textHeightWithText:(NSString *)aText width:(CGFloat)aWidth font:(UIFont *)aFont{    NSMutableAttributedString *content = [[NSMutableAttributedString alloc] initWithString:aText];    // 给字符串设置字体行距等样式    [self addGlobalAttributeWithContent:content font:aFont];    CTFramesetterRef framesetterRef = CTFramesetterCreateWithAttributedString((__bridge CFAttributedStringRef)content);    // 粗略的高度，该高度不准，仅供参考    CGSize suggestSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetterRef, CFRangeMake(0, content.length), NULL, CGSizeMake(aWidth, MAXFLOAT), NULL);    NSLog(@"suggestHeight = %f",suggestSize.height);    CGMutablePathRef pathRef = CGPathCreateMutable();    CGPathAddRect(pathRef, NULL, CGRectMake(0, 0, aWidth, suggestSize.height));    CTFrameRef frameRef = CTFramesetterCreateFrame(framesetterRef, CFRangeMake(0, content.length), pathRef, NULL);    CFArrayRef lines = CTFrameGetLines(frameRef);    CFIndex lineCount = CFArrayGetCount(lines);    NSLog(@"行数 = %ld",lineCount);    // 总高度 = 行数*每行的高度，其中每行的高度为指定的值，不同字体大小不一样    CGFloat accurateHeight = lineCount * (aFont.pointSize * kPerLineRatio);    CGFloat height = accurateHeight;    CFRelease(pathRef);    CFRelease(frameRef);    return height;}#pragma mark - 工具方法#pragma mark 给字符串添加全局属性，比如行距，字体大小，默认颜色+ (void)addGlobalAttributeWithContent:(NSMutableAttributedString *)aContent font:(UIFont *)aFont{    CGFloat lineLeading = kGlobalLineLeading; // 行间距    const CFIndex kNumberOfSettings = 2;    //设置段落格式    CTParagraphStyleSetting lineBreakStyle;    CTLineBreakMode lineBreakMode = kCTLineBreakByWordWrapping;    lineBreakStyle.spec = kCTParagraphStyleSpecifierLineBreakMode;    lineBreakStyle.valueSize = sizeof(CTLineBreakMode);    lineBreakStyle.value = &lineBreakMode;    //设置行距    CTParagraphStyleSetting lineSpaceStyle;    CTParagraphStyleSpecifier spec;    spec = kCTParagraphStyleSpecifierLineSpacingAdjustment;    lineSpaceStyle.spec = spec;    lineSpaceStyle.valueSize = sizeof(CGFloat);    lineSpaceStyle.value = &lineLeading;    // 结构体数组    CTParagraphStyleSetting theSettings[kNumberOfSettings] = {        lineBreakStyle,        lineSpaceStyle,    };    CTParagraphStyleRef theParagraphRef = CTParagraphStyleCreate(theSettings, kNumberOfSettings);    // 将设置的行距应用于整段文字    [aContent addAttribute:NSParagraphStyleAttributeName value:(__bridge id)(theParagraphRef) range:NSMakeRange(0, aContent.length)];    CFStringRef fontName = (__bridge CFStringRef)aFont.fontName;    CTFontRef fontRef = CTFontCreateWithName(fontName, aFont.pointSize, NULL);    // 将字体大小应用于整段文字    [aContent addAttribute:NSFontAttributeName value:(__bridge id)fontRef range:NSMakeRange(0, aContent.length)];    // 给整段文字添加默认颜色    [aContent addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(0, aContent.length)];    // 内存管理    CFRelease(theParagraphRef);    CFRelease(fontRef);}#pragma mark - 一行一行绘制，行高确定，行与行之间对齐- (void)drawRectWithLineByLineAlignment{    // 1.创建需要绘制的文字    NSMutableAttributedString *attributed = [[NSMutableAttributedString alloc] initWithString:self.text];    // 2.设置行距等样式    [[self class] addGlobalAttributeWithContent:attributed font:self.font];    self.textHeight = [[self class] textHeightWithText:self.text width:CGRectGetWidth(self.bounds) font:self.font];    // 3.创建绘制区域，path的高度对绘制有直接影响，如果高度不够，则计算出来的CTLine的数量会少一行或者少多行    CGMutablePathRef path = CGPathCreateMutable();    CGPathAddRect(path, NULL, CGRectMake(0, 0, CGRectGetWidth(self.bounds), self.textHeight*2));    // 4.根据NSAttributedString生成CTFramesetterRef    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attributed);    CTFrameRef ctFrame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, attributed.length), path, NULL);    // 获取上下文    CGContextRef contextRef = UIGraphicsGetCurrentContext();    // 转换坐标系    CGContextSetTextMatrix(contextRef, CGAffineTransformIdentity);    CGContextTranslateCTM(contextRef, 0, self.textHeight); // 此处用计算出来的高度    CGContextScaleCTM(contextRef, 1.0, -1.0);    // 一行一行绘制    CFArrayRef lines = CTFrameGetLines(ctFrame);    CFIndex lineCount = CFArrayGetCount(lines);    CGPoint lineOrigins[lineCount];    // 把ctFrame里每一行的初始坐标写到数组里，注意CoreText的坐标是左下角为原点    CTFrameGetLineOrigins(ctFrame, CFRangeMake(0, 0), lineOrigins);    for (int i = 0; i < lineCount; i++)    {        CGPoint point = lineOrigins[i];        NSLog(@"point.y = %f",point.y);    }    NSLog(@"font.ascender = %f,descender = %f,lineHeight = %f,leading = %f",self.font.ascender,self.font.descender,self.font.lineHeight,self.font.leading);    CGFloat frameY = 0;    NSLog(@"self.textHeight = %f,lineHeight = %f",self.textHeight,self.font.pointSize * kPerLineRatio);    for (CFIndex i = 0; i < lineCount; i++){        // 遍历每一行CTLine        CTLineRef line = CFArrayGetValueAtIndex(lines, i);        CGFloat lineAscent;        CGFloat lineDescent;        CGFloat lineLeading; // 行距        // 该函数除了会设置好ascent,descent,leading之外，还会返回这行的宽度        CTLineGetTypographicBounds(line, &lineAscent, &lineDescent, &lineLeading);        NSLog(@"lineAscent = %f",lineAscent);        NSLog(@"lineDescent = %f",lineDescent);        NSLog(@"lineLeading = %f",lineLeading);        CGPoint lineOrigin = lineOrigins[i];        NSLog(@"i = %ld, lineOrigin = %@",i,NSStringFromCGPoint(lineOrigin));        // 微调Y值，需要注意的是CoreText的Y值是在baseLine处，而不是下方的descent。        CGFloat lineHeight = self.font.pointSize * kPerLineRatio;        frameY = self.textHeight - (i + 1)*lineHeight - self.font.descender;        NSLog(@"frameY = %f",frameY);        lineOrigin.y = frameY;        // 调整坐标        CGContextSetTextPosition(contextRef, lineOrigin.x, lineOrigin.y);        CTLineDraw(line, contextRef);    }    CFRelease(path);    CFRelease(framesetter);    CFRelease(ctFrame);}- (void)drawRect:(CGRect)rect{    [self drawRectWithLineByLineAlignment];}@end
   

.h

#import 
   
    @interface MyView : UIView@property (nonatomic ,copy) NSString *text;@property (nonatomic ,strong) UIFont *font;+ (CGFloat)textHeightWithText:(NSString *)aText width:(CGFloat)aWidth font:(UIFont *)aFont;@end
   

结果

参考