有趣的文字 - 渐变的文字

设置渐变颜色的文字有三种方法：
第一种是通过渐变图片遮罩，colorWithPatternImage
第二种是通过Layer设置渐变颜色
第三种是自定义label在drawRect里绘制渐变
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1. colorWithPatternImage

UILabel *demoLabel = [[UILabel alloc] initWithFrame:CGRectMake(40, 100, 350, 160)];
    demoLabel.text = @"曾经有一份真挚的爱情放在我面前，我没有珍惜！";
    demoLabel.font = [UIFont systemFontOfSize:20];
    demoLabel.numberOfLines = 0;
    demoLabel.textColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"shade"]];
    [self.view addSubview:demoLabel];

@效果图，下方渐变图为引入工程的图片实例

2. 通过Layer设置渐变颜色

UILabel *demoLabel2 = [[UILabel alloc] initWithFrame:CGRectMake(40, 280, 350, 180)];
demoLabel2.text = @"Long long ago, there was a sincer cordial emotion in front of me, but I didn't cherish it. Until it lost, I just regreted at that time. It is only the most suffering thing in the world. If the grandfather of heaven give me the last opportunity. I will say three words to that girl:'I love you!' If it has to add an alloted time. I hope it is 10,000 years. ";
demoLabel2.font = [UIFont systemFontOfSize:20];
demoLabel2.numberOfLines = 0;
demoLabel2.textColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"shade"]];
[self.view addSubview:demoLabel2];

CAGradientLayer *gradientLayer = [CAGradientLayer layer];
gradientLayer.colors = @[(id)[UIColor redColor].CGColor, (id)[UIColor colorWithRed:0.29 green:0.95 blue:0.63 alpha:1.00].CGColor, (id)[UIColor colorWithRed:1.00 green:0.89 blue:0.18 alpha:1.00].CGColor, (id)[UIColor colorWithRed:0.81 green:0.13 blue:0.31 alpha:1.00].CGColor];
//gradientLayer.locations = @[@0, @0.5, @1];// 默认就是均匀分布
gradientLayer.startPoint = CGPointMake(0, 0.5);
gradientLayer.endPoint = CGPointMake(1, 0.5);
gradientLayer.frame = demoLabel2.frame;
gradientLayer.mask = demoLabel2.layer;
demoLabel2.layer.frame = gradientLayer.bounds;
[self.view.layer addSublayer:gradientLayer];

@效果

3. 自定义label在drawRect里绘制渐变

- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    // 获取文字mask
    [@"孙悟空老猴子" drawInRect:self.bounds withAttributes:@{NSFontAttributeName : self.font}];
    CGImageRef textMask = CGBitmapContextCreateImage(context);
    
    // 清空画布
    CGContextClearRect(context, rect);
    
    // 设置蒙层
    CGContextTranslateCTM(context, 0.0, self.bounds.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);
    CGContextClipToMask(context, rect, textMask);
    
    // 绘制渐变
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGFloat locations[] = {0, 0.5, 1};
    CGFloat colors[] = {1.0,0.0,0.0,1.0,
                        0.0,1.0,0.0,1.0,
                        0.0,0.0,1.0,1.0};
    CGGradientRef gradient=CGGradientCreateWithColorComponents(colorSpace, colors, locations, 3);
    CGPoint start = CGPointMake(0, self.bounds.size.height / 2.0);
    CGPoint end = CGPointMake(self.bounds.size.width, self.bounds.size.height / 2.0);
    CGContextDrawLinearGradient(context, gradient, start, end, kCGGradientDrawsBeforeStartLocation);
    
    // 释放
    CGColorSpaceRelease(colorSpace);
    CGGradientRelease(gradient);
    CGImageRelease(textMask);
}

ShadeLabel *label = [[ShadeLabel alloc] initWithFrame:CGRectMake(40, 500, 350, 180)];
    [self.view addSubview:label];

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