请问一下有人遇到过 CAGradientLayer 无法截图的问题

已解决
//绘制渐变
UIColor *firstColor = [[UIColor alloc]initWithCGColor:(CGColorRef)self.bgLayer.colors.firstObject];
UIColor *lastColor = [[UIColor alloc]initWithCGColor:(CGColorRef)self.bgLayer.colors.lastObject];
//创建一个 RGB 的颜色空间
CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB();
//定义渐变颜色数组
CGFloat colors[] = {
firstColor.qmui_red, firstColor.qmui_green, firstColor.qmui_blue, 1.00,
lastColor.qmui_red, lastColor.qmui_green, lastColor.qmui_blue, 1.00
};
CGGradientRef _gradient = CGGradientCreateWithColorComponents(rgb, colors, NULL, sizeof(colors)/(sizeof(colors[0])*4));
UIGraphicsBeginImageContextWithOptions(self.preImage.size, NO, self.preImage.scale);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextInspectContext(context);
CGPoint start = CGPointMake(self.preImage.size.width/2, 0);
CGPoint end = CGPointMake(self.preImage.size.width/2, self.preImage.size.height);
CGContextDrawLinearGradient(context, _gradient, start, end, kCGGradientDrawsBeforeStartLocation);

CGImageRef imageRef = self.preImage.CGImage;
CGImageRef subImageRef = CGImageCreateWithImageInRect(imageRef,CGRectMakeWithSize(self.preImage.size));
CGContextDrawImage(context, CGRectMakeWithSize(self.preImage.size), subImageRef);

UIImage *imageOut = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();