在一些視訊APP中，都可以看到一個將線上視訊轉成GIF圖的功能。下面就來說說思路以及實現。我們知道本地視訊可以生成GIF,那麼將線上視訊擷取成本地視訊不就可以了嗎？經過比較，騰訊視訊App也是這麼做的。話不多說，下面開始上程式碼：
第一步：擷取視訊
#pragma mark -擷取視訊
- (void)interceptVideoAndVideoUrl:(NSURL *)videoUrl withOutPath:(NSString *)outPath outputFileType:(NSString *)outputFileType range:(NSRange)videoRange intercept:(InterceptBlock)interceptBlock {
_interceptBlock =interceptBlock;
//不新增背景音樂
NSURL *audioUrl =nil;
//AVURLAsset此類主要用於獲取媒體資訊，包括視訊、聲音等
AVURLAsset* audioAsset = [[AVURLAsset alloc] initWithURL:audioUrl options:nil];
AVURLAsset* videoAsset = [[AVURLAsset alloc] initWithURL:videoUrl options:nil];
//建立AVMutableComposition物件來新增視訊音訊資源的AVMutableCompositionTrack
AVMutableComposition* mixComposition = [AVMutableComposition composition];
//CMTimeRangeMake(start, duration),start起始時間，duration時長，都是CMTime型別
//CMTimeMake(int64_t value, int32_t timescale)，返回CMTime，value視訊的一個總幀數，timescale是指每秒視訊播放的幀數，視訊播放速率，（value / timescale）才是視訊實際的秒數時長，timescale一般情況下不改變，擷取視訊長度通過改變value的值
//CMTimeMakeWithSeconds(Float64 seconds, int32_t preferredTimeScale)，返回CMTime，seconds擷取時長（單位秒），preferredTimeScale每秒幀數
//開始位置startTime
CMTime startTime = CMTimeMakeWithSeconds(videoRange.location, videoAsset.duration.timescale);
//擷取長度videoDuration
CMTime videoDuration = CMTimeMakeWithSeconds(videoRange.length, videoAsset.duration.timescale);
CMTimeRange videoTimeRange = CMTimeRangeMake(startTime, videoDuration);
//視訊採集compositionVideoTrack
AVMutableCompositionTrack *compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
// 避免陣列越界 tracksWithMediaType 找不到對應的檔案時候返回空陣列
//TimeRange擷取的範圍長度
//ofTrack來源
//atTime插放在視訊的時間位置
[compositionVideoTrack insertTimeRange:videoTimeRange ofTrack:([videoAsset tracksWithMediaType:AVMediaTypeVideo].count>0) ? [videoAsset tracksWithMediaType:AVMediaTypeVideo].firstObject : nil atTime:kCMTimeZero error:nil];
//視訊聲音採集(也可不執行這段程式碼不採集視訊音軌，合併後的視訊檔案將沒有視訊原來的聲音)
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];
//聲音長度擷取範圍==視訊長度
CMTimeRange audioTimeRange = CMTimeRangeMake(kCMTimeZero, videoDuration);
//音訊採集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用於合併檔案，匯出合併後檔案，presetName檔案的輸出型別
AVAssetExportSession *assetExportSession = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetPassthrough];
//混合後的視訊輸出路徑
NSURL *outPutURL = [NSURL fileURLWithPath:outPath];
if ([[NSFileManager defaultManager] fileExistsAtPath:outPath])
{
[[NSFileManager defaultManager] removeItemAtPath:outPath error:nil];
}
//輸出視訊格式
assetExportSession.outputFileType = outputFileType;
assetExportSession.outputURL = outPutURL;
//輸出檔案是否網路優化
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");
}
}
});
}];
}
複製程式碼第二步：本地視訊生成GIF圖
/**
生成GIF圖片
@param videoURL 視訊的路徑URL
@param loopCount 播放次數
@param time 每幀的時間間隔 預設0.25s
@param imagePath 存放GIF圖片的檔案路徑
@param completeBlock 完成的回撥
*/
#pragma mark--製作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);
}
}
複製程式碼經過上面簡單兩步，就可以生成本地的視訊和GIF圖了，儲存在沙盒即可。本地視訊可用AVPlayer播放，GIF圖則用UIWebView或者WKWebView載入即可。最後貼上兩步所用到的方法：
#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 - Helpers
CGImageRef 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
};
}
複製程式碼