绘制旋转的文本用的NSString drawInRect绘制旋转的文本用的NSString draw

2019-05-13 15:31发布

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我发现如何绘制旋转的文本用的NSString drawInRect这个答案:,但我不知道它是如何工作的，因为它只是有点为我工作： https://discussions.apple.com/thread/1779814?start=0&tstart = 0

我的代码如下所示：

           CGContextSaveGState(context);
           CGContextDrawLinearGradient(context, gradient, CGPointMake(0, centY - halfWidth), CGPointMake(0, centY + halfWidth), 0);

            // Add text                
            CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor); 
            NSString *str = @"some test string";

            CGAffineTransform transform1 = CGAffineTransformMakeRotation(M_PI/4);

            CGContextConcatCTM(context, transform1);
            CGContextTranslateCTM(context, 0, 0);
            UIFont *font = [UIFont systemFontOfSize:16.0];

            [str drawInRect:CGRectMake(0, 0, 200, 100) withFont:font lineBreakMode:UILineBreakModeWordWrap alignment:UIBaselineAdjustmentNone];

所以，当我用这个，我看到文本被绘制在x轴下方45度。我想沿着我的LinearGradient垂直绘制文本。所以我想我能做到这一点，通过使用M_PI / 2为90度。我没有看到我的文字虽然。我曾尝试不同的变换的旋转，只有一些看起来像M_PI / 4和M_PI / 8的工作。我认为，如果我用-M_PI / 4它将有文本45度的x轴和M_PI / 2将是x轴低于90度以上。但这两种转了什么。

有什么想法吗？谢谢。

Answer 1:

我认为，这是怎么回事，是因为它通过旋转在原点旋转的情况下，你旋转视图之外的文本的位置。

你旋转后，你需要做一个平移上下文回视图。在下面的例子中，我逆时针旋转90度的范围内。然后，我翻译的上下文的TX高度的距离。

- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext(); 

    CGContextSaveGState(context);

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    // Create the gradient 
    CGColorRef startColor = [UIColor colorWithRed:1.0 green:1.0 blue:1.0 alpha:1.0].CGColor; 
    CGColorRef endColor = [UIColor colorWithRed:200.0/255.0 green:200.0/255.0 blue:200.0/255.0 alpha:1.0].CGColor;
    NSArray *colors = [NSArray arrayWithObjects:(id)startColor, (id)endColor, nil];
    CGFloat locations[] = { 0.0, 1.0 };
    CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (CFArrayRef) colors, locations);
    CGContextDrawLinearGradient(context, gradient, CGPointMake(rect.origin.x + rect.size.width / 2, rect.origin.y), CGPointMake(rect.origin.x + rect.size.width / 2, rect.origin.y + rect.size.height), 0);

    // Create text              
    CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor); 
    NSString *string = @"some test string";
    UIFont *font = [UIFont systemFontOfSize:16.0];

    // Rotate the context 90 degrees (convert to radians)
    CGAffineTransform transform1 = CGAffineTransformMakeRotation(-M_PI_2);
    CGContextConcatCTM(context, transform1); 

    // Move the context back into the view 
    CGContextTranslateCTM(context, -rect.size.height, 0);

    // Draw the string 
    [string drawInRect:rect withFont:font lineBreakMode:UILineBreakModeWordWrap alignment:UITextAlignmentLeft];

    // Clean up 
    CGGradientRelease(gradient);
    CGColorSpaceRelease(colorSpace);

    CGContextRestoreGState(context);
}

需要注意的是，你还可以得到的字符串将如何呈现的尺寸，可以在做计算的文本的对齐方式帮助。

    CGSize stringSize = [string sizeWithFont:font];

Answer 2:

我解决下一个方式这个问题。

1）声明上的NSString类别

@interface NSString (NMSchemeItemDraw)
-(void)  drawWithBasePoint:(CGPoint)basePoint
                    andAngle:(CGFloat)angle
                     andFont:(UIFont*)font;
@end

这个类别将绘制文本与给定的中心点，在一行中，并用给定的字体和角度。

2）这一类的实施是看起来像：

@implementation NSString (NMSchemeItemDraw)

    -(void)  drawWithBasePoint:(CGPoint)basePoint
                     andAngle:(CGFloat)angle
                      andFont:(UIFont *)font{
    CGSize  textSize    =   [self   sizeWithFont:font];

    CGContextRef    context =   UIGraphicsGetCurrentContext();
    CGAffineTransform   t   =   CGAffineTransformMakeTranslation(basePoint.x, basePoint.y);
    CGAffineTransform   r   =   CGAffineTransformMakeRotation(angle);


    CGContextConcatCTM(context, t);
    CGContextConcatCTM(context, r);

    [self   drawAtPoint:CGPointMake(-1 * textSize.width / 2, -1 * textSize.height / 2)
               withFont:font];

    CGContextConcatCTM(context, CGAffineTransformInvert(r));
    CGContextConcatCTM(context, CGAffineTransformInvert(t));
    }
@end

3）现在，我可以在我的使用[UIView drawRect:]方法。例如，在接下来的方式：

 -(void)drawRect:(CGRect)rect{
 NSString* example = @"Title";
 [example drawWithBasePoint:CGPointMake(0.0f, 0.0f)
                   andAngle:M_PI
                    andFont:[UIFont boldSystemFontOfSize:16.0]];
 }

Answer 3:

Here'a KoNEW的回答的更新和简化版本。它保留作为奖金图形上下文的状态。这也是一个简单的功能，而不是一个字符串扩展。

func drawRotatedText(_ text: String, at p: CGPoint, angle: CGFloat, font: UIFont, color: UIColor) {
  // Draw text centered on the point, rotated by an angle in degrees moving clockwise.
  let attrs = [NSFontAttributeName: font, NSForegroundColorAttributeName: color]
  let textSize = text.size(attributes: attrs)
  let c = UIGraphicsGetCurrentContext()!
  c.saveGState()
  // Translate the origin to the drawing location and rotate the coordinate system.
  c.translateBy(x: p.x, y: p.y)
  c.rotate(by: angle * .pi / 180)
  // Draw the text centered at the point.
  text.draw(at: CGPoint(x: -textSize.width / 2, y: -textSize.height / 2), withAttributes: attrs)
  // Restore the original coordinate system.
  c.restoreGState()
}

Answer 4:

KoNew的解决方案在斯威夫特：

extension NSString {

    func drawWithBasePoint(basePoint:CGPoint, angle:CGFloat, font:UIFont) {

        var attrs: NSDictionary = [
            NSFontAttributeName: font
        ]

        var textSize:CGSize = self.sizeWithAttributes(attrs as [NSObject : AnyObject])

        // sizeWithAttributes is only effective with single line NSString text 
        // use boundingRectWithSize for multi line text

        var context: CGContextRef =   UIGraphicsGetCurrentContext()

        var t:CGAffineTransform   =   CGAffineTransformMakeTranslation(basePoint.x, basePoint.y)
        var r:CGAffineTransform   =   CGAffineTransformMakeRotation(angle)


        CGContextConcatCTM(context, t)
        CGContextConcatCTM(context, r)


        self.drawAtPoint(CGPointMake(-1 * textSize.width / 2, -1 * textSize.height / 2), withAttributes: attrs as [NSObject : AnyObject])


        CGContextConcatCTM(context, CGAffineTransformInvert(r))
        CGContextConcatCTM(context, CGAffineTransformInvert(t))


    }


}

使用方法：

let fieldFont = UIFont(name: "Helvetica Neue", size: 14)

myNSString.drawWithBasePoint(CGPointMake(bounds.width/2, bounds.height/2), angle: CGFloat(-M_PI_2), font: fieldFont!)

Answer 5:

感谢为这个职位，和克里斯的回答，和的Arkadiusz的另一个职位的答案。

最后，我解决一个这个问题UILabel子类，命名MyVerticalLabel ，并使其利用垂直文本。

@implementation MyVerticalLabel

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
    // Drawing code

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGAffineTransform transform = CGAffineTransformMakeRotation(-M_PI_2);
    CGContextConcatCTM(context, transform);
    CGContextTranslateCTM(context, -rect.size.height, 0);

    // The drawing rect should be applied with transform to.
    CGRect newRect = CGRectApplyAffineTransform(rect, transform);
    newRect.origin = CGPointZero;

    NSMutableParagraphStyle *textStyle = [[NSMutableParagraphStyle defaultParagraphStyle] mutableCopy];
    textStyle.lineBreakMode = self.lineBreakMode;
    textStyle.alignment = self.textAlignment;

    // Apply current label attributes for drawing function.
    NSDictionary *attributeDict =
    @{
      NSFontAttributeName : self.font,
      NSForegroundColorAttributeName : self.textColor,
      NSParagraphStyleAttributeName : textStyle,
      };
    [self.text drawInRect:newRect withAttributes:attributeDict];
}

@end

文章来源: Drawing rotated text with NSString drawInRect