iOS 合并带有透明通道的视频

视频的合成,透明通道是大家所熟知.
在图形图像学中,透明通道也称Alpha通道,代表数字图像中像素点的透明信息。白色的Alpha像素用以定义不透明的彩色像素,而黑色的Alpha定以透明像素,黑白之间的灰阶则是彩色图片中的半透明部分。—–摘自百度百科所以在合并雪花,灯光,爆破。。。 这里就需要有透明通道的视频。

这里我用的是GPUImage 这个工具,可以讲雪花无缝隙的结合起来,说到这里,大家最好会使用一点ps,在图片滤镜处理的时候,可以通过ps来看看参数和效果
通过ps实验,发现滤色可以做到这一点。GPUImageScreenBlendFilter 可以结局这个事情。
详细的GPUImage的头文件点击这里—-http://blog.csdn.net/think_ma/article/details/43093331

不说了code

 

[objc]

_movieFile = [[GPUImageMovie alloc] initWithURL:url];

_movieFile.runBenchmark = YES;
_movieFile.playAtActualSpeed = NO;
_movieFile2 = [[GPUImageMovie alloc] initWithURL:url2];
_movieFile2.runBenchmark = YES;
_movieFile2.playAtActualSpeed = NO;
_filter = [[GPUImageScreenBlendFilter alloc] init];
// filter = [[GPUImageUnsharpMaskFilter alloc] init];
[_movieFile addTarget:self.filter];
[_movieFile2 addTarget:self.filter];
// Only rotate the video for display, leave orientation the same for recording
// In addition to displaying to the screen, write out a processed version of the movie to disk
NSString *pathToMovie = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/last.mov"];
unlink([pathToMovie UTF8String]); // If a file already exists, AVAssetWriter won’t let you record new frames, so delete the old movie

NSLog(@"file = %@",pathToMovie);
NSURL *movieURL = [NSURL fileURLWithPath:pathToMovie];

self.movieWriter = [[GPUImageMovieWriter alloc] initWithMovieURL:movieURL size:CGSizeMake(640.0, 360.0)];
[self.filter addTarget:self.movieWriter];
// Configure this for video from the movie file, where we want to preserve all video frames and audio samples
self.movieWriter.shouldPassthroughAudio = YES;
//movieFile.audioEncodingTarget = self.movieWriter;
[_movieFile enableSynchronizedEncodingUsingMovieWriter:self.movieWriter];

[self.movieWriter startRecording];
[_movieFile startProcessing];
[_movieFile2 startProcessing];
__block mlkiMovie * sself = self;

[self.movieWriter setCompletionBlock:^{
[sself.filter removeTarget:sself.movieWriter];
[sself.movieFile endProcessing];
[sself.movieFile2 endProcessing];
[sself.movieWriter finishRecording];
NSLog(@"ok");
}];
[/objc]

GPUImageScreenBlendFilter 相当于ps的滤镜。

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