Question

我正在尝试以编程方式在iOS中创建GIF，使用以下堆栈的问题：

Create and and export an animated gif via iOS?

我的代码如下所示：

 // File Parameters
const void *keys[] =   { kCGImagePropertyGIFLoopCount };
const void *values[] = { (CFNumberRef) 0 };

CFDictionaryRef params          = CFDictionaryCreate(NULL, keys, values, 1, NULL, NULL);
const void *keys2[] =   { kCGImagePropertyGIFDictionary };
const void *values2[] = { (CFDictionaryRef) params  };

CFDictionaryRef fileProperties  = CFDictionaryCreate(NULL, keys2 , values2, 1, NULL, NULL);

// URL to the documents directory
NSURL *documentsDirectoryURL  = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:YES error:nil];
NSURL *fileURL                = [documentsDirectoryURL URLByAppendingPathComponent:fileName];

// Object that writes GIF to the specified URL
CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)fileURL, kUTTypeGIF, [arrayOfAllFrames count], NULL);
CGImageDestinationSetProperties(destination, fileProperties);

for (NSUInteger i = 0; i < [arrayOfAllFrames count]; i++) {
    @autoreleasepool {
        float delayTime = [[gifFramesDuration objectAtIndex:i] floatValue]; 
        NSDictionary *frameProperties = @{
                                          (__bridge id)kCGImagePropertyGIFDictionary: @{
                                                  (__bridge id)kCGImagePropertyGIFDelayTime: [NSNumber numberWithFloat:delayTime] // a float (not double!) in seconds, rounded to centiseconds in the GIF data
                                                  }
                                          };

        UIImage *myImage = [arrayOfAllFrames objectAtIndex:i];
        CGImageDestinationAddImage(destination, myImage.CGImage, (__bridge CFDictionaryRef)frameProperties);
    }
}
if (!CGImageDestinationFinalize(destination)) {
    NSLog(@"failed to finalize image destination");
}
CFRelease(destination);
CFRelease(fileProperties);
CFRelease(params);

但是，一旦我尝试向GIF文件添加大约240帧，调试器会在调用CGImageDestinationFinalize后抛出以下错误：

(923,0xb0115000) malloc: *** error for object 0xd1e7204: incorrect checksum for freed object - object was probably modified after being freed.

您能否请我提供一些解决方法，或者建议如何避免使用malloc？

Answer 1

首先，尝试使用Instruments调试您的应用。您可能会注意到该问题是由该方法引起的： Generatefromrgbimagewu

我一直想知道原因是否在我的线程实现中，但事实证明，一旦出现这种错误，你应该专注于调整Image的大小。

图片调整后，上面发布的代码会生成您自己的GIF。

如何在使用CGImageDestinationFinalize时避免使用malloc

1 个答案: