在一些视频APP中，都可以看到一个将在线视频转成GIF图的功能。下面就来说说思路以及实现。我们知道本地视频可以生成GIF,那么将在线视频截取成本地视频不就可以了吗？经过比较，腾讯视频App也是这么做的。话不多说，下面开始上代码：
第一步：截取视频
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#pragma mark -截取视频- (void)interceptVideoAndVideoUrl:(NSURL *)videoUrl withOutPath:(NSString *)outPath outputFileType:(NSString *)outputFileType range:(NSRange)videoRange intercept:(InterceptBlock)interceptBlock { _interceptBlock =interceptBlock; //不添加背景音乐 NSURL *audioUrl =nil; //AVURLAsset此类主要用于获取媒体信息，包括视频、声音等 AVURLAsset* audioAsset = [[AVURLAsset alloc] initWithURL:audioUrl options:nil]; AVURLAsset* videoAsset = [[AVURLAsset alloc] initWithURL:videoUrl options:nil]; //创建AVMutableComposition对象来添加视频音频资源的AVMutableCompositionTrack AVMutableComposition* mixComposition = [AVMutableComposition composition]; //CMTimeRangeMake(start, duration),start起始时间，duration时长，都是CMTime类型 //CMTimeMake(int64_t value, int32_t timescale)，返回CMTime，value视频的一个总帧数，timescale是指每秒视频播放的帧数，视频播放速率，（value / timescale）才是视频实际的秒数时长，timescale一般情况下不改变，截取视频长度通过改变value的值 //CMTimeMakeWithSeconds(Float64 seconds, int32_t preferredTimeScale)，返回CMTime，seconds截取时长（单位秒），preferredTimeScale每秒帧数 //开始位置startTime CMTime startTime = CMTimeMakeWithSeconds(videoRange.location, videoAsset.duration.timescale); //截取长度videoDuration CMTime videoDuration = CMTimeMakeWithSeconds(videoRange.length, videoAsset.duration.timescale); CMTimeRange videoTimeRange = CMTimeRangeMake(startTime, videoDuration); //视频采集compositionVideoTrack AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid]; // 避免数组越界 tracksWithMediaType 找不到对应的文件时候返回空数组 //TimeRange截取的范围长度 //ofTrack来源 //atTime插放在视频的时间位置 [compositionVideoTrack insertTimeRange:videoTimeRange ofTrack:([videoAsset tracksWithMediaType:AVMediaTypeVideo].count>0) ? [videoAsset tracksWithMediaType:AVMediaTypeVideo].firstObject : nil atTime:kCMTimeZero error:nil]; //视频声音采集(也可不执行这段代码不采集视频音轨，合并后的视频文件将没有视频原来的声音) AVMutableCompositionTrack *compositionVoiceTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid]; [compositionVoiceTrack insertTimeRange:videoTimeRange ofTrack:([videoAsset tracksWithMediaType:AVMediaTypeAudio].count>0)?[videoAsset tracksWithMediaType:AVMediaTypeAudio].firstObject:nil atTime:kCMTimeZero error:nil]; //声音长度截取范围==视频长度 CMTimeRange audioTimeRange = CMTimeRangeMake(kCMTimeZero, videoDuration); //音频采集compositionCommentaryTrack AVMutableCompositionTrack *compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid]; [compositionAudioTrack insertTimeRange:audioTimeRange ofTrack:([audioAsset tracksWithMediaType:AVMediaTypeAudio].count > 0) ? [audioAsset tracksWithMediaType:AVMediaTypeAudio].firstObject : nil atTime:kCMTimeZero error:nil]; //AVAssetExportSession用于合并文件，导出合并后文件，presetName文件的输出类型 AVAssetExportSession *assetExportSession = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetPassthrough]; //混合后的视频输出路径 NSURL *outPutURL = [NSURL fileURLWithPath:outPath]; if ([[NSFileManager defaultManager] fileExistsAtPath:outPath]) { [[NSFileManager defaultManager] removeItemAtPath:outPath error:nil]; } //输出视频格式 assetExportSession.outputFileType = outputFileType; assetExportSession.outputURL = outPutURL; //输出文件是否网络优化 assetExportSession.shouldOptimizeForNetworkUse = YES; [assetExportSession exportAsynchronouslyWithCompletionHandler:^{ dispatch_async(dispatch_get_main_queue(), ^{ switch (assetExportSession.status) { case AVAssetExportSessionStatusFailed: if (_interceptBlock) { _interceptBlock(assetExportSession.error,outPutURL); } break; case AVAssetExportSessionStatusCancelled:{ logdebug(@"Export Status: Cancell"); break; } case AVAssetExportSessionStatusCompleted: { if (_interceptBlock) { _interceptBlock(nil,outPutURL); } break; } case AVAssetExportSessionStatusUnknown: { logdebug(@"Export Status: Unknown"); } case AVAssetExportSessionStatusExporting : { logdebug(@"Export Status: Exporting"); } case AVAssetExportSessionStatusWaiting: { logdebug(@"Export Status: Wating"); } } }); }];} |
第二步：本地视频生成GIF图
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/** 生成GIF图片 @param videoURL 视频的路径URL @param loopCount 播放次数 @param time 每帧的时间间隔 默认0.25s @param imagePath 存放GIF图片的文件路径 @param completeBlock 完成的回调 */ #pragma mark--制作GIF- (void)createGIFfromURL:(NSURL*)videoURL loopCount:(int)loopCount delayTime:(CGFloat )time gifImagePath:(NSString *)imagePath complete:(CompleteBlock)completeBlock { _completeBlock =completeBlock; float delayTime = time?:0.25; // Create properties dictionaries NSDictionary *fileProperties = [self filePropertiesWithLoopCount:loopCount]; NSDictionary *frameProperties = [self framePropertiesWithDelayTime:delayTime]; AVURLAsset *asset = [AVURLAsset assetWithURL:videoURL]; float videoWidth = [[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].width; float videoHeight = [[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] naturalSize].height; GIFSize optimalSize = GIFSizeMedium; if (videoWidth >= 1200 || videoHeight >= 1200) optimalSize = GIFSizeVeryLow; else if (videoWidth >= 800 || videoHeight >= 800) optimalSize = GIFSizeLow; else if (videoWidth >= 400 || videoHeight >= 400) optimalSize = GIFSizeMedium; else if (videoWidth < 400|| videoHeight < 400) optimalSize = GIFSizeHigh; // Get the length of the video in seconds float videoLength = (float)asset.duration.value/asset.duration.timescale; int framesPerSecond = 4; int frameCount = videoLength*framesPerSecond; // How far along the video track we want to move, in seconds. float increment = (float)videoLength/frameCount; // Add frames to the buffer NSMutableArray *timePoints = [NSMutableArray array]; for (int currentFrame = 0; currentFrame<frameCount; ++currentFrame) { float seconds = (float)increment * currentFrame; CMTime time = CMTimeMakeWithSeconds(seconds, [timeInterval intValue]); [timePoints addObject:[NSValue valueWithCMTime:time]]; } //completion block NSURL *gifURL = [self createGIFforTimePoints:timePoints fromURL:videoURL fileProperties:fileProperties frameProperties:frameProperties gifImagePath:imagePath frameCount:frameCount gifSize:_gifSize?:GIFSizeMedium]; if (_completeBlock) { // Return GIF URL _completeBlock(_error,gifURL); }} |
经过上面两步，就可以生成本地的视频和GIF图了，存储在沙盒即可。贴上两步所用到的方法：
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#pragma mark - Base methods- (NSURL *)createGIFforTimePoints:(NSArray *)timePoints fromURL:(NSURL *)url fileProperties:(NSDictionary *)fileProperties frameProperties:(NSDictionary *)frameProperties gifImagePath:(NSString *)imagePath frameCount:(int)frameCount gifSize:(GIFSize)gifSize{ NSURL *fileURL = [NSURL fileURLWithPath:imagePath]; if (fileURL == nil) return nil; CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)fileURL, kUTTypeGIF , frameCount, NULL); CGImageDestinationSetProperties(destination, (CFDictionaryRef)fileProperties); AVURLAsset *asset = [AVURLAsset URLAssetWithURL:url options:nil]; AVAssetImageGenerator *generator = [AVAssetImageGenerator assetImageGeneratorWithAsset:asset]; generator.appliesPreferredTrackTransform = YES; CMTime tol = CMTimeMakeWithSeconds([tolerance floatValue], [timeInterval intValue]); generator.requestedTimeToleranceBefore = tol; generator.requestedTimeToleranceAfter = tol; NSError *error = nil; CGImageRef previousImageRefCopy = nil; for (NSValue *time in timePoints) { CGImageRef imageRef; #if TARGET_OS_IPHONE || TARGET_IPHONE_SIMULATOR imageRef = (float)gifSize/10 != 1 ? createImageWithScale([generator copyCGImageAtTime:[time CMTimeValue] actualTime:nil error:&error], (float)gifSize/10) : [generator copyCGImageAtTime:[time CMTimeValue] actualTime:nil error:&error]; #elif TARGET_OS_MAC imageRef = [generator copyCGImageAtTime:[time CMTimeValue] actualTime:nil error:&error]; #endif if (error) { _error =error; logdebug(@"Error copying image: %@", error); return nil; } if (imageRef) { CGImageRelease(previousImageRefCopy); previousImageRefCopy = CGImageCreateCopy(imageRef); } else if (previousImageRefCopy) { imageRef = CGImageCreateCopy(previousImageRefCopy); } else { _error =[NSError errorWithDomain:NSStringFromClass([self class]) code:0 userInfo:@{NSLocalizedDescriptionKey:@"Error copying image and no previous frames to duplicate"}]; logdebug(@"Error copying image and no previous frames to duplicate"); return nil; } CGImageDestinationAddImage(destination, imageRef, (CFDictionaryRef)frameProperties); CGImageRelease(imageRef); } CGImageRelease(previousImageRefCopy); // Finalize the GIF if (!CGImageDestinationFinalize(destination)) { _error =error; logdebug(@"Failed to finalize GIF destination: %@", error); if (destination != nil) { CFRelease(destination); } return nil; } CFRelease(destination); return fileURL;}#pragma mark - HelpersCGImageRef createImageWithScale(CGImageRef imageRef, float scale) { #if TARGET_OS_IPHONE || TARGET_IPHONE_SIMULATOR CGSize newSize = CGSizeMake(CGImageGetWidth(imageRef)*scale, CGImageGetHeight(imageRef)*scale); CGRect newRect = CGRectIntegral(CGRectMake(0, 0, newSize.width, newSize.height)); UIGraphicsBeginImageContextWithOptions(newSize, NO, 0); CGContextRef context = UIGraphicsGetCurrentContext(); if (!context) { return nil; } // Set the quality level to use when rescaling CGContextSetInterpolationQuality(context, kCGInterpolationHigh); CGAffineTransform flipVertical = CGAffineTransformMake(1, 0, 0, -1, 0, newSize.height); CGContextConcatCTM(context, flipVertical); // Draw into the context; this scales the image CGContextDrawImage(context, newRect, imageRef); //Release old image CFRelease(imageRef); // Get the resized image from the context and a UIImage imageRef = CGBitmapContextCreateImage(context); UIGraphicsEndImageContext(); #endif return imageRef;}#pragma mark - Properties- (NSDictionary *)filePropertiesWithLoopCount:(int)loopCount { return @{(NSString *)kCGImagePropertyGIFDictionary: @{(NSString *)kCGImagePropertyGIFLoopCount: @(loopCount)} };}- (NSDictionary *)framePropertiesWithDelayTime:(float)delayTime { return @{(NSString *)kCGImagePropertyGIFDictionary: @{(NSString *)kCGImagePropertyGIFDelayTime: @(delayTime)}, (NSString *)kCGImagePropertyColorModel:(NSString *)kCGImagePropertyColorModelRGB };} |
最后，截取的本地视频可用AVPlayer播放，生成的GIF图则用UIWebView或者WKWebView又或者 YYImage 加载即可。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：https://www.jianshu.com/p/5ea3cbdb17ae
