iOS生成gif图片

前言

记录一下最新遇到的需求，就是在播放的过程中生成gif表情包，这里我选择了iOS系统库CGImageDestinationRef

使用教程

创建CGImageDestinationRef

_url = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, (CFStringRef)_exportURL, kCFURLPOSIXPathStyle, false);
// 300表示预计需要插入的图片，这个值如果小于预设值，CGImageDestinationRef会缓存对应的图片到cache里面，导致存在内存问题。因此，这个值最好设置的比你想插入的值更大一点。
_destination = CGImageDestinationCreateWithURL(_url, kUTTypeGIF, 300, NULL);

配置CGImageDestinationRef

NSMutableDictionary* dict = [NSMutableDictionary dictionaryWithCapacity:2];
[dict setObject:[NSNumber numberWithBool:YES] forKey:(NSString*)kCGImagePropertyGIFHasGlobalColorMap];
[dict setObject:[NSNumber numberWithInt:8] forKey:(NSString*)kCGImagePropertyDepth];
// loop表示循环的次数，0表示无限循环，其他表示循环的次数
[dict setObject:[NSNumber numberWithInt:_loop] forKey:(NSString*)kCGImagePropertyGIFLoopCount];
    
NSDictionary* property = [NSDictionary dictionaryWithObject:dict forKey:(NSString *)kCGImagePropertyGIFDictionary];
CGImageDestinationSetProperties(_destination, (__bridge CFDictionaryRef)property);

添加图片到CGImageDestinationRef

// 指示每一帧之间的duration，单位为秒。
NSMutableDictionary* dict = [NSMutableDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithFloat:0.1],(NSString *)kCGImagePropertyGIFDelayTime, nil];
NSDictionary *properties = [NSDictionary dictionaryWithObject:dict forKey:(NSString *)kCGImagePropertyGIFDictionary];
    
CGImageDestinationAddImage(_destination, cgimage, (__bridge CFDictionaryRef)properties);

结束生成gif图片

CGImageDestinationFinalize(_destination);