Ios CGImageSourceCreateTumbnailAtIndex因20MB图像而崩溃

当我用大图像（即>10MB）测试iPad时，以下创建缩略图的方法会在iPad上崩溃。我已经对它进行了分析，分配没有报告任何大的内存峰值-在操作期间，它始终保持5 MB的活动内存

如何为如此大的图像创建缩略图？我尝试过用核心图形来扩展它，但内存效率较低，不起作用

+(UIImage*) thumbnailImageAtPath:(NSString*) path withSize:(CGSize) size{

    @autoreleasepool{

        CGImageSourceRef src = CGImageSourceCreateWithURL((__bridge CFURLRef)[NSURL fileURLWithPath:path], NULL);

        if(!src){
            return nil;
        }

        NSDictionary* options = @{
                                  (id)kCGImageSourceShouldAllowFloat : (id)kCFBooleanTrue,
                                  (id)kCGImageSourceCreateThumbnailWithTransform : (id)kCFBooleanFalse,
                                  (id)kCGImageSourceCreateThumbnailFromImageIfAbsent : (id)kCFBooleanTrue,
                                  (id)kCGImageSourceThumbnailMaxPixelSize : [NSNumber numberWithDouble:1024]
                                  };

        CGImageRef thumbnail = CGImageSourceCreateThumbnailAtIndex(src, 0, (__bridge CFDictionaryRef)options);

        // Doesn't reach here :(

        UIImage* img = [[UIImage alloc] initWithCGImage:thumbnail];

        NSLog(@"Size: %f, %f", size.width, size.height);

        CGImageRelease(thumbnail);
        CFRelease(src);

        return img;

    }

}

我已经在主线程、工作线程、并发线程、非并发线程等方面进行了尝试，但在实际设备上似乎不起作用

---

另一个奇怪的是，它在大于60 MB的PDF文件中工作得非常出色。

尝试删除选项kCGImageSourceThumbnailMaxPixelSize。。。如果没有，请问我

编辑： 请尝试以下代码：

+ (UIImage*)scaleAndRotateImage:(UIImage *)image{

int kMaxResolution = 1024; // Or whatever 320

CGImageRef imgRef = image.CGImage;

CGFloat width;
CGFloat height;

width = CGImageGetWidth(imgRef);
height = CGImageGetHeight(imgRef);

CGAffineTransform transform = CGAffineTransformIdentity;
CGRect bounds = CGRectMake(0, 0, width, height);
if (width > kMaxResolution || height > kMaxResolution) {
    CGFloat ratio = width/height;
    if (ratio > 1) {
        bounds.size.width = kMaxResolution;
        bounds.size.height = bounds.size.width / ratio;
    }
    else {
        bounds.size.height = kMaxResolution;
        bounds.size.width = bounds.size.height * ratio;
    }
}

CGFloat scaleRatio = bounds.size.width / width;
CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
CGFloat boundHeight;
UIImageOrientation orient = image.imageOrientation;
switch(orient) {

    case UIImageOrientationUp: //EXIF = 1
        transform = CGAffineTransformIdentity;
        break;

    case UIImageOrientationUpMirrored: //EXIF = 2
        transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
        transform = CGAffineTransformScale(transform, -1.0, 1.0);
        break;

    case UIImageOrientationDown: //EXIF = 3
        transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
        transform = CGAffineTransformRotate(transform, M_PI);
        break;

    case UIImageOrientationDownMirrored: //EXIF = 4
        transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
        transform = CGAffineTransformScale(transform, 1.0, -1.0);
        break;

    case UIImageOrientationLeftMirrored: //EXIF = 5
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
        transform = CGAffineTransformScale(transform, -1.0, 1.0);
        transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
        break;

    case UIImageOrientationLeft: //EXIF = 6
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
        transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
        break;

    case UIImageOrientationRightMirrored: //EXIF = 7
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeScale(-1.0, 1.0);
        transform = CGAffineTransformRotate(transform, M_PI / 2.0);
        break;

    case UIImageOrientationRight: //EXIF = 8
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);
        transform = CGAffineTransformRotate(transform, M_PI / 2.0);
        break;

    default:
        [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];

}

UIGraphicsBeginImageContext(bounds.size);

CGContextRef context = UIGraphicsGetCurrentContext();

if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {
    CGContextScaleCTM(context, -scaleRatio, scaleRatio);
    CGContextTranslateCTM(context, -height, 0);
}
else {
    CGContextScaleCTM(context, scaleRatio, -scaleRatio);
    CGContextTranslateCTM(context, 0, -height);
}

CGContextConcatCTM(context, transform);

CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

return imageCopy;}

我想我知道问题出在哪里了

我使用的png中有相当多的alpha透明像素

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不过，我必须对不同的alpha/non-alpha图像运行一些确定的测试，以确认这就是问题所在。当我有机会时，我会这样做。

这不起作用-它继续崩溃，并为加载的所有其他缩略图发出内存警告。几个问题1）到底是什么崩溃？2） 你能主持一个有问题的图像吗？我手头没有任何超大图像3）什么设备和iOS版本？谢谢1） 它只是停止-没有内存警告或异常2）任何图像在访问10MB时都会出现问题。。试试这一款iPadMiniOS6，我应该注意，我只在这台设备和模拟器上试过，因为这是应用程序运行的最低规格设备，在iPadMiniOS6.1.3上运行这一代码，使用这张图片，效果很好。我正在传递一个

{100100}

的大小。你能解释一下上下文吗？你能用“只是停一下”来解释更多吗？它挂起来了吗？是否生成了任何崩溃日志？编辑：我应该注意到墙纸只有10兆。我正在寻找一个更大的，但如果你能主办一个将是一个帮助。谢谢你，还有一个更新——我在维基百科上找到了一个18MB的jpg。到目前为止，100*100、40*40和20*20的传球速度似乎较慢，但没有发生碰撞或悬挂。当然，现在我仔细看看代码，它只记录大小。我认为你的问题中缺少了一些有助于重现问题的上下文。没有日志，没有挂起，什么都没有。它只是停止了。我已经分析过了，仪器中没有异常的记忆尖峰。我已经通过了200x200和100x100两种尺寸的测试，但都崩溃了。在上下文方面：它是一个PNG文件（这会有什么不同吗？），在操作中调用“缩略图创建”方法，并在非并发后台队列中运行。我必须这样做，因为如果我在主线程上生成缩略图，UI将挂起。谢谢您的帮助，顺便说一下：）这不是内存效率，因为您正在将整个图像加载到内存中。

NSString *path = [[NSBundle mainBundle] pathForResource:@"LARGE_elevation" ofType:@"jpg"];

UIImage* image = [UIImage imageWithContentsOfFile:path];
image = [self scaleImage:image toSize:CGSizeMake(400, 200)];

- (UIImage *)scaleImage:(UIImage *)image
                        toSize:(CGSize)size
{
    CGSize sz = image.size;
    if(sz.width > size.width || sz.height > size.height) {
        double ratio = MIN(sz.width / size.width, sz.height / size.height);
        sz.width /= ratio;
        sz.height /= ratio;
    }
    CGContextRef context;
    UIGraphicsBeginImageContextWithOptions(size, NO, image.scale);
    context = UIGraphicsGetCurrentContext();
    CGContextSetGrayFillColor(context, 0.0, 1.0);
    CGContextFillRect(context, CGRectMake(0, 0, size.width, size.height));
    [image drawInRect:CGRectMake(0, 0, sz.width, sz.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}