设置渐变色

向上渐变

BD00FD8A-C7D4-4EDB-9AE0-38748AB42DEC.png

向下渐变

8D6AD23E-DD4D-4877-86C3-892DA074BC43.png

话不多说，上方法

typedef NS_ENUM(NSInteger, DirectionStyle){
    DirectionStyleToUnder = 0,  //向下
    DirectionStyleToUn = 1      //向上
};

/**
 *  渐变色
 *  @param red              红色
 *  @param green            绿色
 *  @param blue             蓝色
 *  @param startAlpha       开始的透明度
 *  @param endAlpha         结束的透明度
 *  @param direction        那个方向
 *  @param frame            大小
 */
- (void)LW_gradientColorWithRed:(CGFloat)red
                          green:(CGFloat)green
                           blue:(CGFloat)blue
                     startAlpha:(CGFloat)startAlpha
                       endAlpha:(CGFloat)endAlpha
                      direction:(DirectionStyle)direction
                          frame:(CGRect)frame
{
    //底部上下渐变效果背景
    // The following methods will only return a 8-bit per channel context in the DeviceRGB color space. 通过图片上下文设置颜色空间间
    UIGraphicsBeginImageContext(frame.size);
    //获得当前的上下文
    CGContextRef context = UIGraphicsGetCurrentContext();
    //创建颜色空间 /* Create a DeviceRGB color space. */
    CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB();
    //通过矩阵调整空间变换
    CGContextScaleCTM(context, frame.size.width, frame.size.height);
    
    //通过颜色组件获得渐变上下文
    CGGradientRef backGradient;
    //253.0/255.0, 163.0/255.0, 87.0/255.0, 1.0,
    if (direction == DirectionStyleToUnder) {
        //向下
        //设置颜色 矩阵
        CGFloat colors[] = {
            red, green, blue, startAlpha,
            red, green, blue, endAlpha,
        };
        backGradient = CGGradientCreateWithColorComponents(rgb, colors, NULL, sizeof(colors)/(sizeof(colors[0])*4));
    } else {
        //向上
        CGFloat colors[] = {
            red, green, blue, endAlpha,
            red, green, blue, startAlpha,
        };
        backGradient = CGGradientCreateWithColorComponents(rgb, colors, NULL, sizeof(colors)/(sizeof(colors[0])*4));
    }
    
    //释放颜色渐变
    CGColorSpaceRelease(rgb);
    //通过上下文绘画线色渐变
    CGContextDrawLinearGradient(context, backGradient, CGPointMake(0.5, 0), CGPointMake(0.5, 1), kCGGradientDrawsBeforeStartLocation);
    //通过图片上下文获得照片
    self.image = UIGraphicsGetImageFromCurrentImageContext();
}

DirectionStyle 设置渐变的方向

PS: 使用方法 [image LW_gradientColorWithRed:255/255.0 green:116/255.0 blue:1/255.0 startAlpha:0.8 endAlpha:0.3 direction:DirectionStyleToUn frame:CGRectMake(10, 400, LWSCREEN_WIDTH-20, 100)];