// 1.创建一行背景图片
CGFloat rowW = self.view.frame.size.width;
CGFloat rowH = 30;
UIGraphicsBeginImageContextWithOptions(CGSizeMake(rowW, rowH), NO, 0.0);
CGContextRef ctx = UIGraphicsGetCurrentContext();
// 画矩形框
[[UIColor redColor] set];
CGContextAddRect(ctx, CGRectMake(0, 0, rowW, rowH));
CGContextFillPath(ctx);
// 画线
[[UIColor greenColor] set];
CGFloat lineWidth = 2;
CGContextSetLineWidth(ctx, lineWidth);
CGFloat dividerX = 0;
CGFloat dividerY = rowH - lineWidth;
CGContextMoveToPoint(ctx, dividerX, dividerY);
CGContextAddLineToPoint(ctx, rowW - dividerX, dividerY);
CGContextStrokePath(ctx);
// 取图
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
// 结束上下文
UIGraphicsEndImageContext();