iOS - 如何在UILabel上实现文本的浮雕效果？

Question

我可以知道如何将浮雕效果作为图片上显示的文字" 提醒 "吗？

它看起来像是嵌入了文本？

谢谢

Answer 1

适用于iOS 7.0的更新

在iOS 7.0中,Apple NSTextEffectAttributeName为属性字符串添加了一个新属性.如果部署目标是iOS 7.0或更高版本,则可以将此属性设置为NSTextEffectLetterpressStyle以浮雕样式绘制属性字符串.

原版的

我不能肯定Apple如何绘制浮雕文字.它看起来像是用红色填充字符串字形,然后在字形的内边缘周围应用阴影,并在字形的顶部外边缘应用非常微弱的阴影.我试了一下,这就是它的样子:

最重要的是我的渲染.下面是一个简单的UILabel,带有影子,克里斯在他的回答中提出.我在后台放了一个Reminders应用程序的屏幕截图.

这是我的代码.

首先,您需要一个能够创建字符串图像蒙版的函数.您将使用蒙版来绘制字符串本身,然后绘制仅出现在字符串内边缘周围的阴影.此图像只有一个alpha通道,没有RGB通道.

- (UIImage *)maskWithString:(NSString *)string font:(UIFont *)font size:(CGSize)size
{
    CGRect rect = { CGPointZero, size };
    CGFloat scale = [UIScreen mainScreen].scale;
    CGColorSpaceRef grayscale = CGColorSpaceCreateDeviceGray();
    CGContextRef gc = CGBitmapContextCreate(NULL, size.width * scale, size.height * scale, 8, size.width * scale, grayscale, kCGImageAlphaOnly);
    CGContextScaleCTM(gc, scale, scale);
    CGColorSpaceRelease(grayscale);
    UIGraphicsPushContext(gc); {
        [[UIColor whiteColor] setFill];
        [string drawInRect:rect withFont:font];
    } UIGraphicsPopContext();

    CGImageRef cgImage = CGBitmapContextCreateImage(gc);
    CGContextRelease(gc);
    UIImage *image = [UIImage imageWithCGImage:cgImage scale:scale orientation:UIImageOrientationDownMirrored];
    CGImageRelease(cgImage);

    return image;
}

其次,您需要一个反转该掩码的函数.您将使用它来使CoreGraphics在字符串的内边缘周围绘制阴影.这需要是一个完整的RGBA图像.(iOS似乎不支持灰度+ alpha图像.)

- (UIImage *)invertedMaskWithMask:(UIImage *)mask
{
    CGRect rect = { CGPointZero, mask.size };
    UIGraphicsBeginImageContextWithOptions(rect.size, NO, mask.scale); {
        [[UIColor blackColor] setFill];
        UIRectFill(rect);
        CGContextClipToMask(UIGraphicsGetCurrentContext(), rect, mask.CGImage);
        CGContextClearRect(UIGraphicsGetCurrentContext(), rect);
    }
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

您可以在函数中使用这些函数,该函数以红色绘制字符串并将阴影应用于其内部边缘.

-(UIImage *)imageWithInteriorShadowAndString:(NSString *)string font:(UIFont *)font textColor:(UIColor *)textColor size:(CGSize)size
{
    CGRect rect = { CGPointZero, size };
    UIImage *mask = [self maskWithString:string font:font size:rect.size];
    UIImage *invertedMask = [self invertedMaskWithMask:mask];
    UIImage *image;
    UIGraphicsBeginImageContextWithOptions(rect.size, NO, [UIScreen mainScreen].scale); {
        CGContextRef gc = UIGraphicsGetCurrentContext();
        // Clip to the mask that only allows drawing inside the string's image.
        CGContextClipToMask(gc, rect, mask.CGImage);
        // We apply the mask twice because we're going to draw through it twice.
        // Only applying it once would make the edges too sharp.
        CGContextClipToMask(gc, rect, mask.CGImage);
        mask = nil; // done with mask; let ARC free it

        // Draw the red text.
        [textColor setFill];
        CGContextFillRect(gc, rect);

        // Draw the interior shadow.
        CGContextSetShadowWithColor(gc, CGSizeZero, 1.6, [UIColor colorWithWhite:.3 alpha:1].CGColor);
        [invertedMask drawAtPoint:CGPointZero];
        invertedMask = nil; // done with invertedMask; let ARC free it

        image = UIGraphicsGetImageFromCurrentImageContext();
    }
    UIGraphicsEndImageContext();
    return image;
}

接下来,您需要一个获取图像并返回带有微弱向上阴影的副本的函数.

- (UIImage *)imageWithUpwardShadowAndImage:(UIImage *)image
{
    UIGraphicsBeginImageContextWithOptions(image.size, NO, image.scale); {
        CGContextSetShadowWithColor(UIGraphicsGetCurrentContext(), CGSizeMake(0, -1), 1, [UIColor colorWithWhite:0 alpha:.15].CGColor);
        [image drawAtPoint:CGPointZero];
    }
    UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return resultImage;
}

最后,您可以组合这些功能来创建字符串的浮雕图像.我把我的最终图像放入一个UIImageView易于测试的地方.

- (void)viewDidLoad
{
    [super viewDidLoad];

    CGRect rect = self.imageView.bounds;
    NSString *string = @"Reminders";
    UIFont *font = [UIFont systemFontOfSize:33];
    UIImage *interiorShadowImage = [self imageWithInteriorShadowAndString:string
        font:font
        textColor:[UIColor colorWithHue:0 saturation:.9 brightness:.7 alpha:1]
        size:rect.size];
    UIImage *finalImage = [self imageWithUpwardShadowAndImage:interiorShadowImage];

    self.imageView.image = finalImage;
}

Answer 2

这看起来就像是文本周围的阴影.您在IB中设置文本颜色的相同区域中设置它 - 为阴影选择合适的颜色并设置阴影偏移的方式(在您发布的示例中,看起来它们将阴影颜色设置为相同的颜色作为文本并将其偏移0水平和-1垂直(这意味着一个像素向上).

在代码中,属性设置如下(假设您已经设置了一个名为"标签"的UILabel:

label.shadowColor = [UIColor blackColor]; // Choose your color here - in the example
                                          // posted, they probably chose a similar color
                                          // to the text color and then set the alpha
                                          // down around 0.7 or so so the shadow would be
                                          // faint.
label.shadowOffset = CGSizeMake(0,-1);    // First parameter is horizontal, second is vertical