iOS 在线视频生成GIF图功能的方法

#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");
    }
     
     
   }
   
   
  });
  
  
 }];
}

/**
 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);
 }

}

#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
   };
}