CGDataProviderCopyData 在内存中堆积导致崩溃
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【中文标题】CGDataProviderCopyData 在内存中堆积导致崩溃【英文标题】:CGDataProviderCopyData builds up in memory causing crash 【发布时间】:2013-08-28 19:25:53 【问题描述】:好的,我正在从服务器上下载一堆大图像(5mb),然后将这些图像拼接在一起,并从一个字节数组中渲染整个图像。但是,我意识到每个图像的数据都没有被释放,因此会导致内存警告和我的应用程序崩溃。我认为由于我的显式 (__bridge_transfer NSData *) 强制转换,ARC 会负责释放对象,但事实证明它仍然是一个问题。在仪器中,大约 1mb 的名为“CGDataProviderCopyData”的对象会堆积起来,并且不会因为每个正在拼接到整个图像中的文件而被丢弃。有什么想法或任何人可以引导我朝着正确的方向前进吗?非常感谢。
// Create array to add all files into total image
NSMutableArray *byteArray = [[NSMutableArray alloc] initWithCapacity:(imageHeight * imageWidth)];
// Iterate through each file in files array
for (NSString *file in array)
// Set baseURL for individual file path
NSString *baseURL = [NSString stringWithFormat:@"http://xx.225.xxx.xxx%@",[imageInfo objectForKey:@"BaseURL"]];
// Specify imagePath by appending baseURL to file name
NSString *imagePath = [NSString stringWithFormat:@"%@%@", baseURL, file];
// Change NSString --> NSURL --> NSData
NSURL *imageUrl = [NSURL URLWithString:imagePath];
NSData *imageData = [NSData dataWithContentsOfURL:imageUrl];
// Create image from imageData
UIImage *image = [UIImage imageWithData:imageData];
CGImageRef cgimage = image.CGImage;
size_t width = CGImageGetWidth(cgimage);
size_t height = CGImageGetHeight(cgimage);
size_t bpr = CGImageGetBytesPerRow(cgimage);
size_t bpp = CGImageGetBitsPerPixel(cgimage);
size_t bpc = CGImageGetBitsPerComponent(cgimage);
size_t bytes_per_pixel = bpp / bpc;
// Get CGDataProviderRef from cgimage
CGDataProviderRef provider = CGImageGetDataProvider(cgimage);
// This is the object that is not being released
NSData *data = (__bridge_transfer NSData *)CGDataProviderCopyData(provider); //Using (__bridge_transfer NSData *) casts the provider to type NSData and gives ownership to ARC, but still not discarded
const UInt8 *bytes = (Byte *)[data bytes];
// Log which file is currently being iterated through
NSLog(@"---Stitching png file to total image: %@", file);
// Populate byte array with channel data from each pixel
for(size_t row = 0; row < height; row++)
for(size_t col = 0; col < width; col++)
const UInt8* pixel =
&bytes[row * bpr + col * bytes_per_pixel];
for(unsigned short i = 0; i < 4; i+=4)
__unused unsigned short red = pixel[i]; // red channel - unused
unsigned short green = pixel[i+1]; // green channel
unsigned short blue = pixel[i+2]; // blue channel
__unused unsigned short alpha = pixel[i+3]; // alpha channel - unused
// Create dicom intensity value from intensity = [(g *250) + b]
unsigned short dicomInt = ((green * 256) + blue);
//Convert unsigned short intensity value to NSNumber so can store in array as object
NSNumber *DICOMvalue = [NSNumber numberWithInt:dicomInt];
// Add to image array (total image)
[byteArray addObject:DICOMvalue];
data = nil;
return byteArray;
通过 Xcode 运行“分析”也不会显示任何明显的泄漏。
【问题讨论】:
【参考方案1】:我拿了这段代码,几乎是一字不差地做了一些调查。使用 CFDataRef/NSData,我能够看到您在 NSDatas 没有消失的情况下看到的问题,并且我能够通过将使用 NSData 的代码部分包装在 @autoreleasepool
范围内来解决它,就像这样:
// Create array to add all files into total image
NSMutableArray *byteArray = [[NSMutableArray alloc] initWithCapacity:(imageHeight * imageWidth)];
// Iterate through each file in files array
for (NSString *file in array)
// Set baseURL for individual file path
NSString *baseURL = [NSString stringWithFormat:@"http://xx.225.xxx.xxx%@",[imageInfo objectForKey:@"BaseURL"]];
// Specify imagePath by appending baseURL to file name
NSString *imagePath = [NSString stringWithFormat:@"%@%@", baseURL, file];
// Change NSString --> NSURL --> NSData
NSURL *imageUrl = [NSURL URLWithString:imagePath];
NSData *imageData = [NSData dataWithContentsOfURL:imageUrl];
// Create image from imageData
UIImage *image = [UIImage imageWithData:imageData];
CGImageRef cgimage = image.CGImage;
size_t width = CGImageGetWidth(cgimage);
size_t height = CGImageGetHeight(cgimage);
size_t bpr = CGImageGetBytesPerRow(cgimage);
size_t bpp = CGImageGetBitsPerPixel(cgimage);
size_t bpc = CGImageGetBitsPerComponent(cgimage);
size_t bytes_per_pixel = bpp / bpc;
// Get CGDataProviderRef from cgimage
CGDataProviderRef provider = CGImageGetDataProvider(cgimage);
@autoreleasepool
// This is the object that is not being released
NSData *data = (__bridge_transfer NSData *)CGDataProviderCopyData(provider); //Using (__bridge_transfer NSData *) casts the provider to type NSData and gives ownership to ARC, but still not discarded
const UInt8 *bytes = (Byte *)[data bytes];
// Log which file is currently being iterated through
NSLog(@"---Stitching png file to total image: %@", file);
// Populate byte array with channel data from each pixel
for(size_t row = 0; row < height; row++)
for(size_t col = 0; col < width; col++)
const UInt8* pixel =
&bytes[row * bpr + col * bytes_per_pixel];
for(unsigned short i = 0; i < 4; i+=4)
__unused unsigned short red = pixel[i]; // red channel - unused
unsigned short green = pixel[i+1]; // green channel
unsigned short blue = pixel[i+2]; // blue channel
__unused unsigned short alpha = pixel[i+3]; // alpha channel - unused
// Create dicom intensity value from intensity = [(g *250) + b]
unsigned short dicomInt = ((green * 256) + blue);
//Convert unsigned short intensity value to NSNumber so can store in array as object
NSNumber *DICOMvalue = [NSNumber numberWithInt:dicomInt];
// Add to image array (total image)
[byteArray addObject:DICOMvalue];
data = nil;
return byteArray;
在添加 @autoreleasepool
之后,我注释掉了您创建 NSNumber 并将它们放入数组中的部分,我能够在 Instruments 的 Allocations 模板中看到确实 CFData现在,随着循环的每一轮,物体都会被释放。
我注释掉创建 NSNumbers 并将它们放入数组的部分的原因是,使用那里的代码,你最终将添加 width * height * 4
NSNumbers 到 byteArray
。这意味着即使 NSData 被正确释放,您的堆使用量也会增加width * height * 4 * <at least 4 bytes, maybe more>
无论如何。也许这就是你需要做的,但这确实让我更难看到 NSDatas 发生了什么,因为它们的大小与 NSNumbers 数组相比相形见绌。
希望对您有所帮助。
【讨论】:
我尝试用 autorelease 包装 for 循环,但仍然没有释放数据对象 @user2525045 经过更多调查编辑 不确定我是否理解您关于堆增长的评论的最后一部分,无论如何。你能澄清一下吗? 这里的代码导致内存被分配并以比 NSData 对象未被释放时更大的速度增长。换句话说,如果在内存中同时拥有 NSData 对象就足以导致您的应用程序被杀死,那么即使在它们被正确释放之后,您仍然会被杀死,因为您正在通过分析创建另一个数据结构比 NSDatas 本身还要大的图像。以上是关于CGDataProviderCopyData 在内存中堆积导致崩溃的主要内容,如果未能解决你的问题,请参考以下文章