GPUImage源碼閱讀（八）

概述

GPUImage是一個(gè)著名的圖像處理開源庫(kù)，它讓你能夠在圖片、視頻、相機(jī)上使用GPU加速的濾鏡和其它特效。與CoreImage框架相比，可以根據(jù)GPUImage提供的接口，使用自定義的濾鏡。項(xiàng)目地址：https://github.com/BradLarson/GPUImage
這篇文章主要是閱讀GPUImage框架中的 GPUImageTwoInputFilter、GPUImageThreeInputFilter、GPUImageFourInputFilter 這幾個(gè)類的源碼。這幾個(gè)類與多個(gè)紋理輸入有關(guān)，都間接或直接繼承自GPUImageFilter，在需要處理多個(gè)紋理輸入的時(shí)候可以使用它們。以下是源碼內(nèi)容：
GPUImageTwoInputFilter
GPUImageThreeInputFilter
GPUImageFourInputFilter

實(shí)現(xiàn)效果

照片.png

GPUImageTwoInputFilter

GPUImageTwoInputFilter 可以接收兩個(gè)幀緩存對(duì)象的輸入。它的作用可以將兩個(gè)幀緩存對(duì)象的輸入合并成一個(gè)幀緩存對(duì)象的輸出。它繼承自GPUImageFilter，因此，可以方便在濾鏡鏈中使用。

實(shí)例變量。GPUImageTwoInputFilter最主要的特點(diǎn)就是增加了secondInputFramebuffer這個(gè)接收第二個(gè)幀緩存對(duì)象的實(shí)例變量，同時(shí)，也增加了關(guān)于第二個(gè)幀緩存對(duì)象的其它相關(guān)參數(shù)。

@interface GPUImageTwoInputFilter : GPUImageFilter
{
    // 與第二個(gè)幀緩存對(duì)象相關(guān)的參數(shù)
    GPUImageFramebuffer *secondInputFramebuffer;
    GLint filterSecondTextureCoordinateAttribute;
    GLint filterInputTextureUniform2;
    GPUImageRotationMode inputRotation2;
    CMTime firstFrameTime, secondFrameTime;
    
    // 控制兩個(gè)幀緩存對(duì)象渲染的相關(guān)參數(shù)
    BOOL hasSetFirstTexture, hasReceivedFirstFrame, hasReceivedSecondFrame, firstFrameWasVideo, secondFrameWasVideo;
    BOOL firstFrameCheckDisabled, secondFrameCheckDisabled;
}

初始化方法。初始化的時(shí)候可以不用指定頂點(diǎn)著色器，但是需要指定片段著色器。

// 初始化方法
- (id)initWithFragmentShaderFromString:(NSString *)fragmentShaderString;
- (id)initWithVertexShaderFromString:(NSString *)vertexShaderString fragmentShaderFromString:(NSString *)fragmentShaderString;

// 指定fragmentShaderString來初始化
- (id)initWithFragmentShaderFromString:(NSString *)fragmentShaderString;
{
    if (!(self = [self initWithVertexShaderFromString:kGPUImageTwoInputTextureVertexShaderString fragmentShaderFromString:fragmentShaderString]))
    {
        return nil;
    }
    
    return self;
}

// 指定vertexShaderString和fragmentShaderString來初始化
- (id)initWithVertexShaderFromString:(NSString *)vertexShaderString fragmentShaderFromString:(NSString *)fragmentShaderString;
{
    if (!(self = [super initWithVertexShaderFromString:vertexShaderString fragmentShaderFromString:fragmentShaderString]))
    {
        return nil;
    }
    // 相關(guān)變量初始化
    inputRotation2 = kGPUImageNoRotation;
    
    hasSetFirstTexture = NO;
    
    hasReceivedFirstFrame = NO;
    hasReceivedSecondFrame = NO;
    firstFrameWasVideo = NO;
    secondFrameWasVideo = NO;
    firstFrameCheckDisabled = NO;
    secondFrameCheckDisabled = NO;
    
    firstFrameTime = kCMTimeInvalid;
    secondFrameTime = kCMTimeInvalid;
        
    runSynchronouslyOnVideoProcessingQueue(^{
        [GPUImageContext useImageProcessingContext];
        // 獲取第二個(gè)紋理坐標(biāo)對(duì)象
        filterSecondTextureCoordinateAttribute = [filterProgram attributeIndex:@"inputTextureCoordinate2"];

        // 獲取第二個(gè)紋理對(duì)象
        filterInputTextureUniform2 = [filterProgram uniformIndex:@"inputImageTexture2"]; // This does assume a name of "inputImageTexture2" for second input texture in the fragment shader
        glEnableVertexAttribArray(filterSecondTextureCoordinateAttribute);
    });
    
    return self;
}

其它方法。GPUImageTwoInputFilter給出的方法比較少，但是這里有一些重寫父類的方法是處理兩個(gè)幀緩存對(duì)象輸入的關(guān)鍵，比如：- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;，- (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates:(const GLfloat *)textureCoordinates;。

// 增加方法
- (void)disableFirstFrameCheck;
- (void)disableSecondFrameCheck;
// 重寫方法
- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;
- (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates:(const GLfloat *)textureCoordinates;


// 需不需要檢查第一個(gè)紋理輸入
- (void)disableFirstFrameCheck;
{
    firstFrameCheckDisabled = YES;
}

// 需不需要檢查第二個(gè)紋理輸入
- (void)disableSecondFrameCheck;
{
    secondFrameCheckDisabled = YES;
}

- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;
{
    // 已經(jīng)接收了兩個(gè)紋理對(duì)象的輸入，則返回
    if (hasReceivedFirstFrame && hasReceivedSecondFrame)
    {
        return;
    }
    
    BOOL updatedMovieFrameOppositeStillImage = NO;
    
    // 處理第一個(gè)紋理對(duì)象
    if (textureIndex == 0)
    {
        hasReceivedFirstFrame = YES;
        firstFrameTime = frameTime;
        // 如果不檢查第二個(gè)紋理輸入，則直接默認(rèn)已經(jīng)接收了第二個(gè)紋理
        if (secondFrameCheckDisabled)
        {
            hasReceivedSecondFrame = YES;
        }
        
        if (!CMTIME_IS_INDEFINITE(frameTime))
        {
            if CMTIME_IS_INDEFINITE(secondFrameTime)
            {
                updatedMovieFrameOppositeStillImage = YES;
            }
        }
    }
    else
    {
        hasReceivedSecondFrame = YES;
        secondFrameTime = frameTime;
        // 如果不檢查第一個(gè)紋理輸入，則直接默認(rèn)已經(jīng)接收了第一個(gè)紋理
        if (firstFrameCheckDisabled)
        {
            hasReceivedFirstFrame = YES;
        }

        if (!CMTIME_IS_INDEFINITE(frameTime))
        {
            if CMTIME_IS_INDEFINITE(firstFrameTime)
            {
                updatedMovieFrameOppositeStillImage = YES;
            }
        }
    }

    // || (hasReceivedFirstFrame && secondFrameCheckDisabled) || (hasReceivedSecondFrame && firstFrameCheckDisabled)
    // 如果接收了兩個(gè)紋理輸入或者是有效幀，則渲染
    if ((hasReceivedFirstFrame && hasReceivedSecondFrame) || updatedMovieFrameOppositeStillImage)
    {
        CMTime passOnFrameTime = (!CMTIME_IS_INDEFINITE(firstFrameTime)) ? firstFrameTime : secondFrameTime;
        [super newFrameReadyAtTime:passOnFrameTime atIndex:0]; // Bugfix when trying to record: always use time from first input (unless indefinite, in which case use the second input)
        hasReceivedFirstFrame = NO;
        hasReceivedSecondFrame = NO;
    }
}

- (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates:(const GLfloat *)textureCoordinates;
{
    if (self.preventRendering)
    {
        [firstInputFramebuffer unlock];
        [secondInputFramebuffer unlock];
        return;
    }
    
    [GPUImageContext setActiveShaderProgram:filterProgram];
    outputFramebuffer = [[GPUImageContext sharedFramebufferCache] fetchFramebufferForSize:[self sizeOfFBO] textureOptions:self.outputTextureOptions onlyTexture:NO];
    [outputFramebuffer activateFramebuffer];
    if (usingNextFrameForImageCapture)
    {
        [outputFramebuffer lock];
    }

    [self setUniformsForProgramAtIndex:0];
        
    glClearColor(backgroundColorRed, backgroundColorGreen, backgroundColorBlue, backgroundColorAlpha);
    glClear(GL_COLOR_BUFFER_BIT);

    // 激活第一個(gè)紋理 
    glActiveTexture(GL_TEXTURE2);
    glBindTexture(GL_TEXTURE_2D, [firstInputFramebuffer texture]);
    glUniform1i(filterInputTextureUniform, 2);  
    
    // 激活第二個(gè)紋理 
    glActiveTexture(GL_TEXTURE3);
    glBindTexture(GL_TEXTURE_2D, [secondInputFramebuffer texture]);
    glUniform1i(filterInputTextureUniform2, 3);
    
    glVertexAttribPointer(filterPositionAttribute, 2, GL_FLOAT, 0, 0, vertices);
    glVertexAttribPointer(filterTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, textureCoordinates);
    glVertexAttribPointer(filterSecondTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, [[self class] textureCoordinatesForRotation:inputRotation2]);
    
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

    [firstInputFramebuffer unlock];
    [secondInputFramebuffer unlock];
    if (usingNextFrameForImageCapture)
    {
        dispatch_semaphore_signal(imageCaptureSemaphore);
    }
}

GPUImageThreeInputFilter

GPUImageThreeInputFilter 可以接收三個(gè)幀緩存對(duì)象的輸入。它的作用可以將三個(gè)幀緩存對(duì)象的輸入合并成一個(gè)幀緩存對(duì)象的輸出。它繼承自GPUImageTwoInputFilter，與GPUImageTwoInputFilter類似，主要增加了第三個(gè)幀緩存對(duì)象處理的相關(guān)操作。

實(shí)例變量。主要增加了與第三個(gè)幀緩存對(duì)象相關(guān)的實(shí)例變量。

@interface GPUImageThreeInputFilter : GPUImageTwoInputFilter
{
    GPUImageFramebuffer *thirdInputFramebuffer;

    GLint filterThirdTextureCoordinateAttribute;
    GLint filterInputTextureUniform3;
    GPUImageRotationMode inputRotation3;
    GLuint filterSourceTexture3;
    CMTime thirdFrameTime;
    
    BOOL hasSetSecondTexture, hasReceivedThirdFrame, thirdFrameWasVideo;
    BOOL thirdFrameCheckDisabled;
}

方法列表。

// 增加方法
- (void)disableThirdFrameCheck;
// 重寫方法
- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;
- (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates:(const GLfloat *)textureCoordinates;


- (void)disableThirdFrameCheck;
{
    thirdFrameCheckDisabled = YES;
}

- (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates:(const GLfloat *)textureCoordinates;
{
    if (self.preventRendering)
    {
        [firstInputFramebuffer unlock];
        [secondInputFramebuffer unlock];
        [thirdInputFramebuffer unlock];
        return;
    }
    
    [GPUImageContext setActiveShaderProgram:filterProgram];
    outputFramebuffer = [[GPUImageContext sharedFramebufferCache] fetchFramebufferForSize:[self sizeOfFBO] textureOptions:self.outputTextureOptions onlyTexture:NO];
    [outputFramebuffer activateFramebuffer];
    if (usingNextFrameForImageCapture)
    {
        [outputFramebuffer lock];
    }

    [self setUniformsForProgramAtIndex:0];
    
    glClearColor(backgroundColorRed, backgroundColorGreen, backgroundColorBlue, backgroundColorAlpha);
    glClear(GL_COLOR_BUFFER_BIT);

    // 激活第一個(gè)紋理
    glActiveTexture(GL_TEXTURE2);
    glBindTexture(GL_TEXTURE_2D, [firstInputFramebuffer texture]);
    glUniform1i(filterInputTextureUniform, 2);
    
    // 激活第二個(gè)紋理
    glActiveTexture(GL_TEXTURE3);
    glBindTexture(GL_TEXTURE_2D, [secondInputFramebuffer texture]);
    glUniform1i(filterInputTextureUniform2, 3);

    // 激活第三個(gè)紋理
    glActiveTexture(GL_TEXTURE4);
    glBindTexture(GL_TEXTURE_2D, [thirdInputFramebuffer texture]);
    glUniform1i(filterInputTextureUniform3, 4);

    glVertexAttribPointer(filterPositionAttribute, 2, GL_FLOAT, 0, 0, vertices);
    glVertexAttribPointer(filterTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, textureCoordinates);
    glVertexAttribPointer(filterSecondTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, [[self class] textureCoordinatesForRotation:inputRotation2]);
    glVertexAttribPointer(filterThirdTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, [[self class] textureCoordinatesForRotation:inputRotation3]);
    
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
    [firstInputFramebuffer unlock];
    [secondInputFramebuffer unlock];
    [thirdInputFramebuffer unlock];
    if (usingNextFrameForImageCapture)
    {
        dispatch_semaphore_signal(imageCaptureSemaphore);
    }
}

- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;
{
    // You can set up infinite update loops, so this helps to short circuit them
    if (hasReceivedFirstFrame && hasReceivedSecondFrame && hasReceivedThirdFrame)
    {
        return;
    }
    
    BOOL updatedMovieFrameOppositeStillImage = NO;
    
    if (textureIndex == 0)
    {
        hasReceivedFirstFrame = YES;
        firstFrameTime = frameTime;
        // 如果不檢查第二個(gè)紋理輸入，則直接默認(rèn)已經(jīng)接收了第二個(gè)紋理
        if (secondFrameCheckDisabled)
        {
            hasReceivedSecondFrame = YES;
        }
        // 如果不檢查第三個(gè)紋理輸入，則直接默認(rèn)已經(jīng)接收了第三個(gè)紋理
        if (thirdFrameCheckDisabled)
        {
            hasReceivedThirdFrame = YES;
        }
        
        if (!CMTIME_IS_INDEFINITE(frameTime))
        {
            if CMTIME_IS_INDEFINITE(secondFrameTime)
            {
                updatedMovieFrameOppositeStillImage = YES;
            }
        }
    }
    else if (textureIndex == 1)
    {
        hasReceivedSecondFrame = YES;
        secondFrameTime = frameTime;
        // 如果不檢查第一個(gè)紋理輸入，則直接默認(rèn)已經(jīng)接收了第一個(gè)紋理
        if (firstFrameCheckDisabled)
        {
            hasReceivedFirstFrame = YES;
        }
        // 如果不檢查第三個(gè)紋理輸入，則直接默認(rèn)已經(jīng)接收了第三個(gè)紋理
        if (thirdFrameCheckDisabled)
        {
            hasReceivedThirdFrame = YES;
        }

        if (!CMTIME_IS_INDEFINITE(frameTime))
        {
            if CMTIME_IS_INDEFINITE(firstFrameTime)
            {
                updatedMovieFrameOppositeStillImage = YES;
            }
        }
    }
    else
    {
        hasReceivedThirdFrame = YES;
        thirdFrameTime = frameTime;
        // 如果不檢查第一個(gè)紋理輸入，則直接默認(rèn)已經(jīng)接收了第一個(gè)紋理
        if (firstFrameCheckDisabled)
        {
            hasReceivedFirstFrame = YES;
        }
        // 如果不檢查第二個(gè)紋理輸入，則直接默認(rèn)已經(jīng)接收了第二個(gè)紋理
        if (secondFrameCheckDisabled)
        {
            hasReceivedSecondFrame = YES;
        }
        
        if (!CMTIME_IS_INDEFINITE(frameTime))
        {
            if CMTIME_IS_INDEFINITE(firstFrameTime)
            {
                updatedMovieFrameOppositeStillImage = YES;
            }
        }
    }
    
    // || (hasReceivedFirstFrame && secondFrameCheckDisabled) || (hasReceivedSecondFrame && firstFrameCheckDisabled)
    // 如果已經(jīng)接收了三個(gè)紋理輸入或者是有效幀，則渲染
    if ((hasReceivedFirstFrame && hasReceivedSecondFrame && hasReceivedThirdFrame) || updatedMovieFrameOppositeStillImage)
    {
        static const GLfloat imageVertices[] = {
            -1.0f, -1.0f,
            1.0f, -1.0f,
            -1.0f,  1.0f,
            1.0f,  1.0f,
        };
        
        [self renderToTextureWithVertices:imageVertices textureCoordinates:[[self class] textureCoordinatesForRotation:inputRotation]];
        
        [self informTargetsAboutNewFrameAtTime:frameTime];

        hasReceivedFirstFrame = NO;
        hasReceivedSecondFrame = NO;
        hasReceivedThirdFrame = NO;
    }
}

GPUImageFourInputFilter

GPUImageFourInputFilter 可以接收四個(gè)幀緩存對(duì)象的輸入。它的作用可以將四個(gè)幀緩存對(duì)象的輸入合并成一個(gè)幀緩存對(duì)象的輸出。它繼承自GPUImageThreeInputFilter，與GPUImageTwoInputFilter、GPUImageThreeInputFilter類似，主要增加了第四個(gè)幀緩存對(duì)象處理的相關(guān)操作。

實(shí)例變量。主要增加了與第四個(gè)幀緩存對(duì)象相關(guān)的實(shí)例變量。

@interface GPUImageFourInputFilter : GPUImageThreeInputFilter
{
    GPUImageFramebuffer *fourthInputFramebuffer;

    GLint filterFourthTextureCoordinateAttribute;
    GLint filterInputTextureUniform4;
    GPUImageRotationMode inputRotation4;
    GLuint filterSourceTexture4;
    CMTime fourthFrameTime;
    
    BOOL hasSetThirdTexture, hasReceivedFourthFrame, fourthFrameWasVideo;
    BOOL fourthFrameCheckDisabled;
}

方法列表。 GPUImageFourInputFilter與GPUImageTwoInputFilter、GPUImageThreeInputFilter相比，它們的一些關(guān)鍵方法的邏輯都比較類似。

// 增加方法
- (void)disableFourthFrameCheck;
// 重寫方法
- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;
- (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates:(const GLfloat *)textureCoordinates;


- (void)disableFourthFrameCheck;
{
    fourthFrameCheckDisabled = YES;
}

- (void)renderToTextureWithVertices:(const GLfloat *)vertices textureCoordinates:(const GLfloat *)textureCoordinates;
{
    if (self.preventRendering)
    {
        [firstInputFramebuffer unlock];
        [secondInputFramebuffer unlock];
        [thirdInputFramebuffer unlock];
        [fourthInputFramebuffer unlock];
        return;
    }
    
    [GPUImageContext setActiveShaderProgram:filterProgram];
    outputFramebuffer = [[GPUImageContext sharedFramebufferCache] fetchFramebufferForSize:[self sizeOfFBO] textureOptions:self.outputTextureOptions onlyTexture:NO];
    [outputFramebuffer activateFramebuffer];
    if (usingNextFrameForImageCapture)
    {
        [outputFramebuffer lock];
    }

    [self setUniformsForProgramAtIndex:0];
    
    glClearColor(backgroundColorRed, backgroundColorGreen, backgroundColorBlue, backgroundColorAlpha);
    glClear(GL_COLOR_BUFFER_BIT);
    
    // 激活紋理對(duì)象
    glActiveTexture(GL_TEXTURE2);
    glBindTexture(GL_TEXTURE_2D, [firstInputFramebuffer texture]);
    glUniform1i(filterInputTextureUniform, 2);
    
    // 激活紋理對(duì)象
    glActiveTexture(GL_TEXTURE3);
    glBindTexture(GL_TEXTURE_2D, [secondInputFramebuffer texture]);
    glUniform1i(filterInputTextureUniform2, 3);

    // 激活紋理對(duì)象
    glActiveTexture(GL_TEXTURE4);
    glBindTexture(GL_TEXTURE_2D, [thirdInputFramebuffer texture]);
    glUniform1i(filterInputTextureUniform3, 4);
    
    // 激活紋理對(duì)象
    glActiveTexture(GL_TEXTURE5);
    glBindTexture(GL_TEXTURE_2D, [fourthInputFramebuffer texture]);
    glUniform1i(filterInputTextureUniform4, 5);

    glVertexAttribPointer(filterPositionAttribute, 2, GL_FLOAT, 0, 0, vertices);
    glVertexAttribPointer(filterTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, textureCoordinates);
    glVertexAttribPointer(filterSecondTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, [[self class] textureCoordinatesForRotation:inputRotation2]);
    glVertexAttribPointer(filterThirdTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, [[self class] textureCoordinatesForRotation:inputRotation3]);
    glVertexAttribPointer(filterFourthTextureCoordinateAttribute, 2, GL_FLOAT, 0, 0, [[self class] textureCoordinatesForRotation:inputRotation4]);
    
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
    [firstInputFramebuffer unlock];
    [secondInputFramebuffer unlock];
    [thirdInputFramebuffer unlock];
    [fourthInputFramebuffer unlock];
    if (usingNextFrameForImageCapture)
    {
        dispatch_semaphore_signal(imageCaptureSemaphore);
    }
}

- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;
{
    // You can set up infinite update loops, so this helps to short circuit them
    if (hasReceivedFirstFrame && hasReceivedSecondFrame && hasReceivedThirdFrame)
    {
        return;
    }
    
    BOOL updatedMovieFrameOppositeStillImage = NO;
    
    if (textureIndex == 0)
    {
        hasReceivedFirstFrame = YES;
        firstFrameTime = frameTime;
        if (secondFrameCheckDisabled)
        {
            hasReceivedSecondFrame = YES;
        }
        if (thirdFrameCheckDisabled)
        {
            hasReceivedThirdFrame = YES;
        }
        if (fourthFrameCheckDisabled)
        {
            hasReceivedThirdFrame = YES;
        }
        
        if (!CMTIME_IS_INDEFINITE(frameTime))
        {
            if CMTIME_IS_INDEFINITE(secondFrameTime)
            {
                updatedMovieFrameOppositeStillImage = YES;
            }
        }
    }
    else if (textureIndex == 1)
    {
        hasReceivedSecondFrame = YES;
        secondFrameTime = frameTime;
        if (firstFrameCheckDisabled)
        {
            hasReceivedFirstFrame = YES;
        }
        if (thirdFrameCheckDisabled)
        {
            hasReceivedThirdFrame = YES;
        }
        if (fourthFrameCheckDisabled)
        {
            hasReceivedFourthFrame = YES;
        }

        if (!CMTIME_IS_INDEFINITE(frameTime))
        {
            if CMTIME_IS_INDEFINITE(firstFrameTime)
            {
                updatedMovieFrameOppositeStillImage = YES;
            }
        }
    }
    else if (textureIndex == 2)
    {
        hasReceivedThirdFrame = YES;
        thirdFrameTime = frameTime;
        if (firstFrameCheckDisabled)
        {
            hasReceivedFirstFrame = YES;
        }
        if (secondFrameCheckDisabled)
        {
            hasReceivedSecondFrame = YES;
        }
        if (fourthFrameCheckDisabled)
        {
            hasReceivedFourthFrame = YES;
        }

        if (!CMTIME_IS_INDEFINITE(frameTime))
        {
            if CMTIME_IS_INDEFINITE(firstFrameTime)
            {
                updatedMovieFrameOppositeStillImage = YES;
            }
        }
    }
    else
    {
        hasReceivedFourthFrame = YES;
        fourthFrameTime = frameTime;
        if (firstFrameCheckDisabled)
        {
            hasReceivedFirstFrame = YES;
        }
        if (secondFrameCheckDisabled)
        {
            hasReceivedSecondFrame = YES;
        }
        if (thirdFrameCheckDisabled)
        {
            hasReceivedThirdFrame = YES;
        }
        
        if (!CMTIME_IS_INDEFINITE(frameTime))
        {
            if CMTIME_IS_INDEFINITE(firstFrameTime)
            {
                updatedMovieFrameOppositeStillImage = YES;
            }
        }
    }
    
    // || (hasReceivedFirstFrame && secondFrameCheckDisabled) || (hasReceivedSecondFrame && firstFrameCheckDisabled)
    // 如果已經(jīng)接收四個(gè)紋理輸入或者是有效幀，則渲染
    if ((hasReceivedFirstFrame && hasReceivedSecondFrame && hasReceivedThirdFrame && hasReceivedFourthFrame) || updatedMovieFrameOppositeStillImage)
    {
        static const GLfloat imageVertices[] = {
            -1.0f, -1.0f,
            1.0f, -1.0f,
            -1.0f,  1.0f,
            1.0f,  1.0f,
        };
        
        [self renderToTextureWithVertices:imageVertices textureCoordinates:[[self class] textureCoordinatesForRotation:inputRotation]];
        
        [self informTargetsAboutNewFrameAtTime:frameTime];

        hasReceivedFirstFrame = NO;
        hasReceivedSecondFrame = NO;
        hasReceivedThirdFrame = NO;
        hasReceivedFourthFrame = NO;
    }
}

實(shí)現(xiàn)過程

先加載圖片，然后分別經(jīng)過兩個(gè)濾鏡處理，再將處理后的結(jié)果輸出到GPUImageTwoInputFilter中處理，最后用GPUImageView顯示處理后的結(jié)果。

// 圖片
GPUImagePicture *picture = [[GPUImagePicture alloc] initWithImage:[UIImage imageNamed:@"1.jpg"]];

// 濾鏡
GPUImageCannyEdgeDetectionFilter *cannyFilter = [[GPUImageCannyEdgeDetectionFilter alloc] init];
GPUImageGammaFilter *gammaFilter = [[GPUImageGammaFilter alloc] init];

[picture addTarget:cannyFilter];
[picture addTarget:gammaFilter];

// GPUImageTwoInputFilter
GPUImageTwoInputFilter *twoFilter = [[GPUImageTwoInputFilter alloc] initWithFragmentShaderFromString:kTwoInputFragmentShaderString];

[cannyFilter addTarget:twoFilter];
[gammaFilter addTarget:twoFilter];
[twoFilter addTarget:_imageView];

[picture processImage];

片段著色器程序

NSString *const kTwoInputFragmentShaderString = SHADER_STRING
(
 varying highp vec2 textureCoordinate;
 varying highp vec2 textureCoordinate2;
 
 uniform sampler2D inputImageTexture;
 uniform sampler2D inputImageTexture2;
 
 void main()
 {
     highp vec4 oneInputColor = texture2D(inputImageTexture, textureCoordinate);
     highp vec4 twoInputColor = texture2D(inputImageTexture2, textureCoordinate2);
     
     highp float range = distance(textureCoordinate, vec2(0.5, 0.5));
     
     highp vec4 dstClor = oneInputColor;
     if (range < 0.25) {
         dstClor = twoInputColor;
     }else {
         //dstClor = vec4(vec3(1.0 - oneInputColor), 1.0);
         if (oneInputColor.r < 0.001 && oneInputColor.g < 0.001 && oneInputColor.b < 0.001) {
             dstClor = vec4(1.0);
         }else {
             dstClor = vec4(1.0, 0.0, 0.0, 1.0);
         }
     }
     
     gl_FragColor = dstClor;
 }
);

總結(jié)

GPUImageTwoInputFilter、GPUImageThreeInputFilter、GPUImageFourInputFilter 這幾個(gè)類在我們需要合并多個(gè)濾鏡處理結(jié)果的時(shí)候會(huì)很有用，在使用的時(shí)候也比較簡(jiǎn)單。當(dāng)然在GPUImage框架中已有很多濾鏡繼承自這幾個(gè)類，可以處理多個(gè)紋理的輸入。

源碼地址：GPUImage源碼閱讀系列 https://github.com/QinminiOS/GPUImage
系列文章地址：GPUImage源碼閱讀 http://www.lxweimin.com/nb/11749791

最后編輯于：2017.12.07 14:46:05

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三个男躁一个女,国精产品一区一手机的秘密,麦子交换系列最经典十句话,欧美国产综合欧美视频

GPUImage源碼閱讀（八）

GPUImage源碼閱讀（八）

概述

實(shí)現(xiàn)效果

GPUImageTwoInputFilter

GPUImageThreeInputFilter

GPUImageFourInputFilter

實(shí)現(xiàn)過程

總結(jié)

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三个男躁一个女,国精产品一区一手机的秘密,麦子交换系列最经典十句话,欧美 国产 综合 欧美 视频

GPUImage源碼閱讀（八）

概述

實(shí)現(xiàn)效果

GPUImageTwoInputFilter

GPUImageThreeInputFilter

GPUImageFourInputFilter

實(shí)現(xiàn)過程

總結(jié)

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三个男躁一个女,国精产品一区一手机的秘密,麦子交换系列最经典十句话,欧美国产综合欧美视频