少年辛苦终身事，莫向光阴惰寸功。这篇文章主要讲述IOS技术分享| 在iOS WebRTC 中添加美颜滤镜相关的知识，希望能为你提供帮助。
在使用WebRTC的时候，对视频进行美颜处理一般有两种方式：替换WebRTC中的采集模块和对视频数据进行美颜。
一、替换WebRTC中的采集模块
替换WebRTC中的采集模块，相对比较简单，使用GPUImageVideoCamera替换WebRTC中的视频采集，得到经过GPUImage添加美颜处理后的图像，发送给WebRTC的OnFrame方法。
参考基于WebRTC框架开发的全平台推拉流SDK：Github
设置美颜

- (void)setBeautyFace:(BOOL)beautyFace{ if(_beautyFace == beautyFace) return; _beautyFace = beautyFace; [_emptyFilter removeAllTargets]; [_filter removeAllTargets]; [_videoCamera removeAllTargets]; if(_beautyFace){ _filter = [[GPUImageBeautifyFilter alloc] init]; _emptyFilter = [[GPUImageEmptyFilter alloc] init]; }else{ _filter = [[GPUImageEmptyFilter alloc] init]; }__weak typeof(self) _self = self; [_filter setFrameProcessingCompletionBlock:^(GPUImageOutput *output, CMTime time) { [_self processVideo:output]; }]; [_videoCamera addTarget:_filter]; if (beautyFace) { [_filter addTarget:_emptyFilter]; if(_gpuImageView) [_emptyFilter addTarget:_gpuImageView]; } else { if(_gpuImageView) [_filter addTarget:_gpuImageView]; } }

格式转换GPUImage处理后的Pixel格式为BGRA,当处理完成后需要转换为I420格式，用于内部处理和渲染。

-(void) processVideo:(GPUImageOutput *)output{ rtc::CritScope cs(& cs_capture_); if (!_isRunning) { return; } @autoreleasepool { GPUImageFramebuffer *imageFramebuffer = output.framebufferForOutput; size_t width = imageFramebuffer.size.width; size_t height = imageFramebuffer.size.height; uint32_t size = width * height * 3 / 2; if(self.nWidth != width || self.nHeight != height) { self.nWidth = width; self.nHeight = height; if(_dst) delete[] _dst; _dst = NULL; } if(_dst == NULL) { _dst = new uint8_t[size]; } uint8_t* y_pointer = (uint8_t*)_dst; uint8_t* u_pointer = (uint8_t*)y_pointer + width*height; uint8_t* v_pointer = (uint8_t*)u_pointer + width*height/4; int y_pitch = width; int u_pitch = (width + 1) > > 1; int v_pitch = (width + 1) > > 1; libyuv::ARGBToI420([imageFramebuffer byteBuffer], width * 4, y_pointer, y_pitch, u_pointer, u_pitch, v_pointer, v_pitch, width, height); if(self.bVideoEnable) libyuv::I420Rect(y_pointer, y_pitch, u_pointer, u_pitch, v_pointer, v_pitch, 0, 0, width, height, 32, 128, 128); if(_capturer != nil) _capturer-> CaptureYUVData(_dst, width, height, size); } }

美颜后的数据发送给WebRTC的OnFrame方法GPUImageVideoCapturer 类为GPUImage 封装的摄像头类，跟WebRTC中的采集类功能保持一致，继承 cricket::VideoCapturer 类，便可以往WebRTC中塞入采集的音视频流。

namespace webrtc { // 继承cricket::VideoCapturer class GPUImageVideoCapturer : public cricket::VideoCapturer { ... } }

void GPUImageVideoCapturer::CaptureYUVData(const webrtc::VideoFrame& frame, int width, int height) { VideoCapturer::OnFrame(frame, width, height); }

二、对视频数据进行美颜
对视频数据美颜的思路就是传统的第三方美颜SDK的做法，对内部采集的音视频数据进行处理：内部采集的数据（CVPixelBufferRef）-》转换为纹理（GLuint）-》对纹理进行音视频的美颜-》美颜的纹理转换为ios的采集数据（CVPixelBufferRef）-》返回给WebRTC内部进行渲染编码和传输。
同步线程内部处理的一般都是使用同步线程，这样能够保证数据线性流动，参阅GPUImage中的代码片段

runSynchronouslyOnVideoProcessingQueue(^{ // 美颜处理 });

把CVPixelBufferRef 数据转换为纹理（GLuint） RGB格式类型的转换方式

• CoreVideo框架的方法：使用此方法可以创建CVOpenGLESTextureRef纹理，并通过CVOpenGLESTextureGetName(texture)获取纹理id。
  

  - (GLuint)convertRGBPixelBufferToTexture:(CVPixelBufferRef)pixelBuffer { if (!pixelBuffer) { return 0; } CGSize textureSize = CGSizeMake(CVPixelBufferGetWidth(pixelBuffer), CVPixelBufferGetHeight(pixelBuffer)); CVOpenGLESTextureRef texture = nil; CVReturn status = CVOpenGLESTextureCacheCreateTextureFromImage(nil, [[GPUImageContext sharedImageProcessingContext] coreVideoTextureCache], pixelBuffer, nil, GL_TEXTURE_2D, GL_RGBA, textureSize.width, textureSize.height, GL_BGRA, GL_UNSIGNED_BYTE, 0, & texture); if (status != kCVReturnSuccess) { NSLog(@"Can\'t create texture"); } self.renderTexture = texture; return CVOpenGLESTextureGetName(texture); }

  
  
• OpenGL的方法：创建纹理对象，使用glTexImage2D方法上传CVPixelBufferRef中图像数据data到纹理对象中。
  

  glBindTexture(GL_TEXTURE_2D, [outputFramebuffer texture]); glTexImage2D(GL_TEXTURE_2D, 0, _pixelFormat==GPUPixelFormatRGB ? GL_RGB : GL_RGBA, (int)uploadedImageSize.width, (int)uploadedImageSize.height, 0, (GLint)_pixelFormat, (GLenum)_pixelType, bytesToUpload);

  
  

YUV格式类型的转换方式

- (GLuint)convertYUVPixelBufferToTexture:(CVPixelBufferRef)pixelBuffer { if (!pixelBuffer) { return 0; }CGSize textureSize = CGSizeMake(CVPixelBufferGetWidth(pixelBuffer), CVPixelBufferGetHeight(pixelBuffer)); [EAGLContext setCurrentContext:self.context]; GLuint frameBuffer; GLuint textureID; // FBO glGenFramebuffers(1, & frameBuffer); glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer); // texture glGenTextures(1, & textureID); glBindTexture(GL_TEXTURE_2D, textureID); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, textureSize.width, textureSize.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, textureID, 0); glViewport(0, 0, textureSize.width, textureSize.height); // program glUseProgram(self.yuvConversionProgram); // texture CVOpenGLESTextureRef luminanceTextureRef = nil; CVOpenGLESTextureRef chrominanceTextureRef = nil; CVReturn status = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, self.textureCache, pixelBuffer, nil, GL_TEXTURE_2D, GL_LUMINANCE, textureSize.width, textureSize.height, GL_LUMINANCE, GL_UNSIGNED_BYTE, 0, & luminanceTextureRef); if (status != kCVReturnSuccess) { NSLog(@"Can\'t create luminanceTexture"); }status = CVOpenGLESTextureCacheCreateTextureFromImage(kCFAllocatorDefault, self.textureCache, pixelBuffer, nil, GL_TEXTURE_2D, GL_LUMINANCE_ALPHA, textureSize.width / 2, textureSize.height / 2, GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, 1, & chrominanceTextureRef); if (status != kCVReturnSuccess) { NSLog(@"Can\'t create chrominanceTexture"); }glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, CVOpenGLESTextureGetName(luminanceTextureRef)); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glUniform1i(glGetUniformLocation(self.yuvConversionProgram, "luminanceTexture"), 0); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, CVOpenGLESTextureGetName(chrominanceTextureRef)); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glUniform1i(glGetUniformLocation(self.yuvConversionProgram, "chrominanceTexture"), 1); GLfloat kXDXPreViewColorConversion601FullRange[] = { 1.0,1.0,1.0, 0.0,-0.343, 1.765, 1.4,-0.711, 0.0, }; GLuint yuvConversionMatrixUniform = glGetUniformLocation(self.yuvConversionProgram, "colorConversionMatrix"); glUniformMatrix3fv(yuvConversionMatrixUniform, 1, GL_FALSE, kXDXPreViewColorConversion601FullRange); // VBO glBindBuffer(GL_ARRAY_BUFFER, self.VBO); GLuint positionSlot = glGetAttribLocation(self.yuvConversionProgram, "position"); glEnableVertexAttribArray(positionSlot); glVertexAttribPointer(positionSlot, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0); GLuint textureSlot = glGetAttribLocation(self.yuvConversionProgram, "inputTextureCoordinate"); glEnableVertexAttribArray(textureSlot); glVertexAttribPointer(textureSlot, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3* sizeof(float))); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); glDeleteFramebuffers(1, & frameBuffer); glBindFramebuffer(GL_FRAMEBUFFER, 0); glBindBuffer(GL_ARRAY_BUFFER, 0); glFlush(); self.luminanceTexture = luminanceTextureRef; self.chrominanceTexture = chrominanceTextureRef; if (luminanceTextureRef) { CFRelease(luminanceTextureRef); } if (chrominanceTextureRef) { CFRelease(chrominanceTextureRef); }return textureID; }

使用GPUImageTextureInput 加载滤镜和使用GPUImageTextureOutput输出数据

[GPUImageContext setActiveShaderProgram:nil]; GPUImageTextureInput *textureInput = [[ARGPUImageTextureInput alloc] initWithTexture:textureID size:size]; GPUImageSmoothToonFilter *filter = [[GPUImageSmoothToonFilter alloc] init]; [textureInput addTarget:filter]; GPUImageTextureOutput *textureOutput = [[GPUImageTextureOutput alloc] init]; [filter addTarget:textureOutput]; [textureInput processTextureWithFrameTime:kCMTimeZero];

得到textureOutput，即得到输出的纹理。
GPUImageTextureOutput纹理转化为CVPixelBufferRef 数据

- (CVPixelBufferRef)convertTextureToPixelBuffer:(GLuint)texture textureSize:(CGSize)textureSize { [EAGLContext setCurrentContext:self.context]; CVPixelBufferRef pixelBuffer = [self createPixelBufferWithSize:textureSize]; GLuint targetTextureID = [self convertRGBPixelBufferToTexture:pixelBuffer]; GLuint frameBuffer; // FBO glGenFramebuffers(1, & frameBuffer); glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer); // texture glBindTexture(GL_TEXTURE_2D, targetTextureID); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, textureSize.width, textureSize.height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, targetTextureID, 0); glViewport(0, 0, textureSize.width, textureSize.height); // program glUseProgram(self.normalProgram); // texture glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glUniform1i(glGetUniformLocation(self.normalProgram, "renderTexture"), 0); // VBO glBindBuffer(GL_ARRAY_BUFFER, self.VBO); GLuint positionSlot = glGetAttribLocation(self.normalProgram, "position"); glEnableVertexAttribArray(positionSlot); glVertexAttribPointer(positionSlot, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)0); GLuint textureSlot = glGetAttribLocation(self.normalProgram, "inputTextureCoordinate"); glEnableVertexAttribArray(textureSlot); glVertexAttribPointer(textureSlot, 2, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void*)(3* sizeof(float))); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); glDeleteFramebuffers(1, & frameBuffer); glBindFramebuffer(GL_FRAMEBUFFER, 0); glBindBuffer(GL_ARRAY_BUFFER, 0); glFlush(); return pixelBuffer; }

把美颜后的CVPixelBufferRef同步返回给SDK，进行渲染传输。
三、总结
【IOS技术分享| 在iOS WebRTC 中添加美颜滤镜】对音视频的美颜，已经成为了音视频应用的常用功能，除了上述两种做法外，还可以使用第三方美颜，一般音视频厂商都有提供自采集功能，而第三方美颜功能则提供有采集美颜相机功能，二者正好可以无缝结合。如果自身的应用中对美颜要求不是很高，采用音视频SDK自带的美颜即可（美白、美颜、红润），如果用在娱乐场景，除了美颜，还要美型（廋脸，大眼）、贴纸（2D、3D）的，必须要集成第三方美颜SDK了。

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