需求是連接打印機劈榨，將文本內容生成圖片然后裁剪之后傳輸給打印機打印。生成圖片之后效果
大概原理是拿到View的上下文的范圍晦嵌，然后根據(jù)上下文生成圖片
核心代碼
/*
self.makeView 視圖
self.all 整體獲取視圖顯示ImageView
self.part 裁剪之后圖片顯示ImageView
*/
//獲取上下文范圍
UIGraphicsBeginImageContext(self.makeView.bounds.size);
//呈現(xiàn)
[self.makeView.layer renderInContext:UIGraphicsGetCurrentContext()];
//根據(jù)當前上下文生成圖片
UIImage *allImage = UIGraphicsGetImageFromCurrentImageContext();
CGRect rect = CGRectMake(0, 0, 30, 10);
//根據(jù)CGRect裁剪圖片
UIImage *partImage = [UIImage imageWithCGImage:CGImageCreateWithImageInRect(allImage.CGImage, rect)];
//釋放
UIGraphicsEndImageContext();
self.all.image = allImage;
self.part.image = partImage;
