渐变色可以作为视频的图片的placeholderImage,方便字体的显示，用代码生成layer层减少内存的消耗。

图片发自简书App

CAGradientLayer+NIPExtension.h

#import <QuartzCore/QuartzCore.h>
@interface CAGradientLayer (NIPExtension)
/**
 *  生成一个渐变色的layer
 *
 *  @param frame      layer的尺寸
 *  @param startPoint 渐变色的起始位置(范围：0-1)
 *  @param endPoint   渐变色的终止位置(范围：0-1）
 *  @param colors     颜色数组
 *  @param locations  颜色分割点 (范围：0-1)
 *
 *  @return 返回一个渐变色layer
 */
+ (instancetype)gradientLayerWithFrame:(CGRect)frame startPoint:(CGPoint)startPoint endPoint:(CGPoint)endPoint colors:(NSArray<UIColor *>*)colors locations:(NSArray*)locations;
@end

CAGradientLayer+NIPExtension.m

#import "CAGradientLayer+NIPExtension.h"

@implementation CAGradientLayer (NIPExtension)
+ (instancetype)gradientLayerWithFrame:(CGRect)frame startPoint:(CGPoint)startPoint endPoint:(CGPoint)endPoint colors:(NSArray<UIColor *> *)colors locations:(NSArray *)locations
{
    // 生成一个渐变色的layer
    CAGradientLayer * layer = [CAGradientLayer layer];
    
    // 设置尺寸
    layer.frame = frame;
    
    // 渐变色区域的开始位置（位置范围 0 - 1）
    layer.startPoint = startPoint;
    
    // 渐变色区域的结束位置
    layer.endPoint = endPoint;
    
    // 设置颜色数组
    NSMutableArray * colorRefs = [NSMutableArray array];
    for (UIColor *color in colors) {
        [colorRefs addObject:(__bridge id)color.CGColor];
    }
    layer.colors = colorRefs;
    
    // 设置颜色的分割点（范围：0-1）
    layer.locations = locations;
    return layer;
}
@end

补上效果图：

xiaoguotu .png

补充：
线性渐变和径向渐变

- (void)drawLineGradientView{
    // 1.创建颜色空间
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    
    // 2.创建渐变色
    CGFloat components[8] = {229/255.0,77/255.0,65/255.0,1.0,
                            236/255.0,116/255.0,79/255.0,1.0};
//    CGFloat locations[2] = {0.5,0.9};
    CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace,
                                                                 components,
                                                                 NULL,
                                                                 2);
    
    // 3.设置剪裁区域
    CGRect rect = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);
    CGContextClipToRect(UIGraphicsGetCurrentContext(), rect);
    
    // 4.绘制渐变色
    CGContextDrawLinearGradient(UIGraphicsGetCurrentContext(),
                                gradient,
                                CGPointMake(0, 0),
                                CGPointMake(0, self.frame.size.height),
                                kCGGradientDrawsAfterEndLocation|kCGGradientDrawsBeforeStartLocation);
    
    // 释放对象
    CGColorSpaceRelease(colorSpace);
    CGGradientRelease(gradient);
    
}

径向渐变

- (void)drawRadialGradientView{
    // 1、创建颜色空间
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    // 2、创建渐变色
    CGFloat components[8] = {236/255.0,116/255.0,79/255.0,1.0,224/255.0,77/255.0,68/255.0,1.0};
//    CGFloat locations[2] = {0.3,1.0};
    CGGradientRef gradient = CGGradientCreateWithColorComponents(colorSpace,
                                                                 components,
                                                                 NULL,
                                                                 2);
    
    // 3、绘制渐变色
    CGContextDrawRadialGradient(UIGraphicsGetCurrentContext(),
                                gradient,
                                CGPointMake(self.center.x, self.center.y),
                                0,
                                CGPointMake(self.center.x, self.center.y),
                                160,
                                kCGGradientDrawsBeforeStartLocation | kCGGradientDrawsAfterEndLocation);
    // 4、释放对象
    CGColorSpaceRelease(colorSpace);
    CGGradientRelease(gradient);
}