怎样将UIImage对象保存到JPG或者PNG文件中？

【原文：http://blog.csdn.net/wherejaly/article/details/5538248】

我们都知道如果要从data中或者file中读取数据并包装成UIImage可以使用+ imageWithData: 和+ imageWithContentsOfFile: 但如果想把UIImage的图片数据写入到jpg或者png格式的文件中呢？答案是UIImageJPEGRepresentation，请看如下代码

/ Create paths to output images
NSString  *pngPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Test.png"];
NSString  *jpgPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/Test.jpg"];
 
// Write a UIImage to JPEG with minimum compression (best quality)
// The value 'image' must be a UIImage object
// The value '1.0' represents image compression quality as value from 0.0 to 1.0
[UIImageJPEGRepresentation(image, 1.0) writeToFile:jpgPath atomically:YES];
 
// Write image to PNG
[UIImagePNGRepresentation(image) writeToFile:pngPath atomically:YES];
 
// Let's check to see if files were successfully written...
 
// Create file manager
NSError *error;
NSFileManager *fileMgr = [NSFileManager defaultManager];
 
// Point to Document directory
NSString *documentsDirectory = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];
 
// Write out the contents of home directory to console
NSLog(@"Documents directory: %@", [fileMgr contentsOfDirectoryAtPath:documentsDirectory error:&error]);

参考资料：http://iphonedevelopertips.com/data-file-management/save-uiimage-object-as-a-png-or-jpeg-file.html