Save UIImage Object as a PNG or JPEG File

最新推荐文章于 2024-07-08 17:33:40 发布

转载最新推荐文章于 2024-07-08 17:33:40 发布 · 1k 阅读

文章标签：

#object #compression #image #application #file #download

iPhone开发专栏收录该内容

50 篇文章

订阅专栏

本文介绍如何将UIImage对象从相机或其他来源保存为PNG或JPEG文件，并将其写入Documents目录中。文中提供了具体的代码实现，包括设置图片路径、写入不同格式的图片以及检查文件是否成功写入的方法。

Save UIImage Object as a PNG or JPEG File

Posted on March 4, 2010 by John Muchow in Data / File Management

In an earlier post on saving images from the camera to the Photo Album, a question was posed asking how to save the image to another directory other than the Photo Album. Let’s walk through one way to write a UIImage object, from the camera or otherwise, as a PNG or JPG file into the Documents directory.

Get UIImage Data as PNG or JPEG

UIKit includes two C functions, UIImageJPEGRepresentation and UIImagePNGRepresentationwhich will return an NSData object that represents an image in JPEG or PNG format, respectively. With this information in hand, you can then use the writeToFile method of theNSData object to write the image data to a specified path.

// 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]);

Important note, on lines 6 and 9, the value image must be a UIImage object.

Source Code

I’ve changed the example from the original post that wrote a UIImage from the camera to the Photo Album, to write instead to the test files shown above. You can download the source code for the application here: Write UIImage Object as a PNG or JPEG File.