//NSData转换为UIImage
//OC
NSData *imageData = [NSData dataWithContentsOfFile: imagePath];
UIImage *image = [UIImage imageWithData: imageData];
//UIImage转换为NSData
NSData *imageData = UIImagePNGRepresentation(image);
//UIImage转换为 JPEG 图片的 NSData 第二个参数代表压缩程度 取值范围 0 到 1
NSData *imageData = UIImageJPEGRepresentation(image, 0.4f);
//swift
var sourceData = NSData.init()
var image = UIImage.init(data: sourceData as Data)
var data = UIImagePNGRepresentation(image!)
