我找到了关于如何使用 NSString drawInRect: 绘制旋转文本的答案，但我不确定它是如何工作的，因为它只对我有用：https://discussions.apple.com/thread/1779814?start =0&t开始=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];
所以当我使用它时，我看到文本被绘制在 x 轴下方 45 度的位置。我想沿着我的线性渐变垂直绘制文本。所以我想我可以通过使用 M_PI/2 90 度来做到这一点。但我没有看到我的文字。我尝试了不同的旋转变换，但只有一些似乎可以工作，例如 M_PI/4 和 M_PI/8。我认为如果我使用 -M_PI/4 ，文本将在 x 轴上方 45 度，而 M_PI/2 将在 x 轴下方 90 度。但两者都一无所获。
有什么想法吗？谢谢。
我用下面的方法解决这个问题。
1）在 NSString 上声明类别
@interface NSString (NMSchemeItemDraw)
-(void) drawWithBasePoint:(CGPoint)basePoint
andAngle:(CGFloat)angle
andFont:(UIFont*)font;
@end
此类别将使用给定的中心点、一行、给定的字体和角度绘制文本。
2）该类别的实现如下所示：
@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
[UIView drawRect:] -(void)drawRect:(CGRect)rect{
NSString* example = @"Title";
[example drawWithBasePoint:CGPointMake(0.0f, 0.0f)
andAngle:M_PI
andFont:[UIFont boldSystemFontOfSize:16.0]];
}
我认为发生的情况是您将文本旋转到视图之外的位置，因为它通过以原点为中心旋转上下文。
旋转后，您需要进行翻译以将上下文移回到视图中。在下面的示例中，我将上下文逆时针旋转 90 度。然后我将上下文的 tx 翻译为高度的距离。
- (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);
}
请注意，您还可以获得字符串呈现方式的大小，这有助于计算文本的对齐方式。
CGSize stringSize = [string sizeWithFont:font];
这是 KoNEW 答案的更新和简化版本。作为奖励，它保留了图形上下文的状态。这也是一个简单的函数，而不是字符串扩展。
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()
}
KoNew 在 Swift 中的解决方案：
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!)
@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
用途：
enum StringOrigin: Int { case
upperLeft, upperCenter, upperRight,
centerLeft, centerCenter, centerRight,
lowerLeft, lowerCenter, lowerRight }
func drawRotatedAttrString(_ s: NSAttributedString, p: CGPoint, angle: CGFloat, origin: StringOrigin) {
let width = s.size().width
let height = s.size().height
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 offset to handle "origin" choice
switch origin {
case .upperLeft:
s.draw(at: .zero)
case .upperCenter:
s.draw(at: CGPoint(x: -0.5 * width, y: 0))
case .upperRight:
s.draw(at: CGPoint(x: -width, y: 0))
case .centerLeft:
s.draw(at: CGPoint(x: 0, y: -0.5 * height))
case .centerCenter:
s.draw(at: CGPoint(x: -0.5 * width, y: -0.5 * height))
case .centerRight:
s.draw(at: CGPoint(x: -width, y: -0.5 * height))
case .lowerLeft:
s.draw(at: CGPoint(x: 0, y: -height))
case .lowerCenter:
s.draw(at: CGPoint(x: -0.5 * width, y: -height))
case .lowerRight:
s.draw(at: CGPoint(x: -width, y: -height))
}
// Restore the original coordinate system.
c.restoreGState()
}
self.someImageView.image = UIImage(named: "icon")?.addTopRightVerticalText("Hello World")