GPUImage源码解读(六)

介绍GPUImage框架中的GPUImageInput协议以及GPUImageOutput类

GPUImageInput

• GPUImageInput 在GPUImageContext.h中定义, 协议提供了方法列表，细节由实现的对象实现。GPUImage中实现GPUImageInput的协议的类比较多，常见的有 GPUImageFilter、GPUImageView、GPUImageRawDataOutput、GPUImageMovieWriter 等。GPUImageInput 、GPUImageOutput 是构成GPUImage响应链的基础。如果一个类实现了 GPUImageInput 协议我们可以知道它能够接收帧缓存对象的输入，如果继承了 GPUImageOutput 类，我们可以知道它能够输出帧缓存对象。如果两个都具备，则表明既能处理输入又可以输出，比如 GPUImageFilter ，而这就是响应链的基本要求.

@protocol GPUImageInput <NSObject>
// 准备下一个要使用的帧
- (void)newFrameReadyAtTime:(CMTime)frameTime atIndex:(NSInteger)textureIndex;
// 设置输入的帧缓冲对象以及纹理索引
- (void)setInputFramebuffer:(GPUImageFramebuffer *)newInputFramebuffer atIndex:(NSInteger)textureIndex;
// 下一个有效的纹理索引
- (NSInteger)nextAvailableTextureIndex;
// 设置目标的尺寸
- (void)setInputSize:(CGSize)newSize atIndex:(NSInteger)textureIndex;
// 设置旋转模式
- (void)setInputRotation:(GPUImageRotationMode)newInputRotation atIndex:(NSInteger)textureIndex;
// 输出缓冲区的最大尺寸
- (CGSize)maximumOutputSize;
// 输入处理结束
- (void)endProcessing;
// 是否忽略渲染目标的更新
- (BOOL)shouldIgnoreUpdatesToThisTarget;
// 是否启用渲染目标
- (BOOL)enabled;
// 是否为单色输入
- (BOOL)wantsMonochromeInput;
// 设置单色输入
- (void)setCurrentlyReceivingMonochromeInput:(BOOL)newValue;

GPUImageOutput

• GPUImageOutput 表示该类能够作为输出，输出的是 GPUImageFramebuffer 对象。该类的实现比较简单，主要是实现了一些最基本的方法，这些方法不需要依赖具体细节，细节处理在子类中完成。继承 GPUImageOutput 的类也比较多，比如：GPUImageFilter、GPUImageVideoCamera、GPUImageStillCamera、GPUImagePicture 等

• 基本属性

@interface GPUImageOutput : NSObject
{
    // 输出的帧缓存对象
    GPUImageFramebuffer *outputFramebuffer;

   // target列表，target纹理索引列表
    NSMutableArray *targets, *targetTextureIndices;

    // 纹理尺寸
    CGSize inputTextureSize, cachedMaximumOutputSize, forcedMaximumSize;
    BOOL overrideInputSize;
    BOOL allTargetsWantMonochromeData;

    // 设置下一帧提取图片
    BOOL usingNextFrameForImageCapture;
}
// 是否使用mipmaps
@property(readwrite, nonatomic) BOOL shouldSmoothlyScaleOutput;
// 是否忽略处理当前Target
@property(readwrite, nonatomic) BOOL shouldIgnoreUpdatesToThisTarget;
@property(readwrite, nonatomic, retain) GPUImageMovieWriter *audioEncodingTarget;
// 当前忽略处理的Target
@property(readwrite, nonatomic, unsafe_unretained) id<GPUImageInput> targetToIgnoreForUpdates;
// 每帧处理完回调
@property(nonatomic, copy) void(^frameProcessingCompletionBlock)(GPUImageOutput*, CMTime);
// 是否启用渲染目标
@property(nonatomic) BOOL enabled;
// 纹理选项
@property(readwrite, nonatomic) GPUTextureOptions outputTextureOptions;

• 方法列表。GPUImageOutput 提供方法主要是以下几种类型：1、帧缓冲对象管理；2、响应链的管理；3、图像提取。

//只有在MAC 会调用, 在生成 uiimage 使用
// For now, just redefine this on the Mac
typedef NS_ENUM(NSInteger, UIImageOrientation) {
    UIImageOrientationUp,            // default orientation
    UIImageOrientationDown,          // 180 deg rotation
    UIImageOrientationLeft,          // 90 deg CCW
    UIImageOrientationRight,         // 90 deg CW
    UIImageOrientationUpMirrored,    // as above but image mirrored along other axis. horizontal flip
    UIImageOrientationDownMirrored,  // horizontal flip
    UIImageOrientationLeftMirrored,  // vertical flip
    UIImageOrientationRightMirrored, // vertical flip
};
#endif

//定义不同的线程队列
void runOnMainQueueWithoutDeadlocking(void (^block)(void));
void runSynchronouslyOnVideoProcessingQueue(void (^block)(void));
void runAsynchronouslyOnVideoProcessingQueue(void (^block)(void));
void runSynchronouslyOnContextQueue(GPUImageContext *context, void (^block)(void));
void runAsynchronouslyOnContextQueue(GPUImageContext *context, void (^block)(void));
void reportAvailableMemoryForGPUImage(NSString *tag);

@class GPUImageMovieWriter;

/** GPUImage's base source object

 Images or frames of video are uploaded from source objects, which are subclasses of GPUImageOutput. These include:

 - GPUImageVideoCamera (for live video from an iOS camera)
 - GPUImageStillCamera (for taking photos with the camera)
 - GPUImagePicture (for still images)
 - GPUImageMovie (for movies)

 Source objects upload still image frames to OpenGL ES as textures, then hand those textures off to the next objects in the processing chain.
 */
@interface GPUImageOutput : NSObject
{
    // 输出的帧缓存对象
    GPUImageFramebuffer *outputFramebuffer;

    // target列表，target纹理索引列表
    NSMutableArray *targets, *targetTextureIndices;

    // 纹理尺寸
    CGSize inputTextureSize, cachedMaximumOutputSize, forcedMaximumSize;
    BOOL overrideInputSize;
    BOOL allTargetsWantMonochromeData;

    // 设置下一帧提取图片
    BOOL usingNextFrameForImageCapture;
}
// 是否使用mipmaps
@property(readwrite, nonatomic) BOOL shouldSmoothlyScaleOutput;
// 是否忽略处理当前Target
@property(readwrite, nonatomic) BOOL shouldIgnoreUpdatesToThisTarget;
@property(readwrite, nonatomic, retain) GPUImageMovieWriter *audioEncodingTarget;
// 当前忽略处理的Target
@property(readwrite, nonatomic, unsafe_unretained) id<GPUImageInput> targetToIgnoreForUpdates;
// 每帧处理完回调
@property(nonatomic, copy) void(^frameProcessingCompletionBlock)(GPUImageOutput*, CMTime);
// 是否启用渲染目标
@property(nonatomic) BOOL enabled;
// 纹理选项
@property(readwrite, nonatomic) GPUTextureOptions outputTextureOptions;


/// @name Managing targets
// 设置输入的帧缓冲对象以及纹理索引
- (void)setInputFramebufferForTarget:(id<GPUImageInput>)target atIndex:(NSInteger)inputTextureIndex;
// 输出的帧缓冲对象
- (GPUImageFramebuffer *)framebufferForOutput;
// 删除帧缓冲对象
- (void)removeOutputFramebuffer;
// 通知所有的Target
- (void)notifyTargetsAboutNewOutputTexture;

/** Returns an array of the current targets. 所有的Target列表
 */
- (NSArray*)targets;

// 增加Target
/** Adds a target to receive notifications when new frames are available.

 The target will be asked for its next available texture.

 See [GPUImageInput newFrameReadyAtTime:]

 @param newTarget Target to be added
 */
- (void)addTarget:(id<GPUImageInput>)newTarget;

// 增加Target
/** Adds a target to receive notifications when new frames are available.

 See [GPUImageInput newFrameReadyAtTime:]

 @param newTarget Target to be added
 */
- (void)addTarget:(id<GPUImageInput>)newTarget atTextureLocation:(NSInteger)textureLocation;

// 删除Target
/** Removes a target. The target will no longer receive notifications when new frames are available.

 @param targetToRemove Target to be removed
 */
- (void)removeTarget:(id<GPUImageInput>)targetToRemove;

// 删除Target
/** Removes all targets.
 */
- (void)removeAllTargets;

/// @name Manage the output texture  强制按照传入的尺寸处理

- (void)forceProcessingAtSize:(CGSize)frameSize;
- (void)forceProcessingAtSizeRespectingAspectRatio:(CGSize)frameSize;

/// @name Still image processing
// 从帧缓冲对象提取CGImage图像
- (void)useNextFrameForImageCapture;
- (CGImageRef)newCGImageFromCurrentlyProcessedOutput;

//使用静态图片做滤镜纹理 方法内会使用 GPUImagePicture创建
- (CGImageRef)newCGImageByFilteringCGImage:(CGImageRef)imageToFilter;

// Platform-specific image output methods
// If you're trying to use these methods, remember that you need to set -useNextFrameForImageCapture before running -processImage or running video and calling any of these methods, or you will get a nil image
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
// 从帧缓冲对象提取UIImage图像
- (UIImage *)imageFromCurrentFramebuffer;
- (UIImage *)imageFromCurrentFramebufferWithOrientation:(UIImageOrientation)imageOrientation;
// 使用静态图片做滤镜纹理
- (UIImage *)imageByFilteringImage:(UIImage *)imageToFilter;
- (CGImageRef)newCGImageByFilteringImage:(UIImage *)imageToFilter;
#else
//mac 环境使用
- (NSImage *)imageFromCurrentFramebuffer;
- (NSImage *)imageFromCurrentFramebufferWithOrientation:(UIImageOrientation)imageOrientation;
- (NSImage *)imageByFilteringImage:(NSImage *)imageToFilter;
- (CGImageRef)newCGImageByFilteringImage:(NSImage *)imageToFilter;
#endif

// 是否提供单色输出 默认为 NO
- (BOOL)providesMonochromeOutput;

• 帧缓冲对象管理。包含了设置输入的帧缓冲对象，获取输出的帧缓冲对象，以及移除输的帧缓冲对象。

  ```

• (void)setInputFramebufferForTarget:(id)target atIndex:(NSInteger)inputTextureIndex; { [target setInputFramebuffer:[self framebufferForOutput] atIndex:inputTextureIndex]; }

• (GPUImageFramebuffer *)framebufferForOutput; { return outputFramebuffer; }

• (void)removeOutputFramebuffer; { outputFramebuffer = nil; }

  ```

• 响应链管理。包含了增加Target，删除Target，处理完成后通知各个Target处理。

- (void)notifyTargetsAboutNewOutputTexture;
{
    for (id<GPUImageInput> currentTarget in targets)
    {
        NSInteger indexOfObject = [targets indexOfObject:currentTarget];
        NSInteger textureIndex = [[targetTextureIndices objectAtIndex:indexOfObject] integerValue];

        [self setInputFramebufferForTarget:currentTarget atIndex:textureIndex];
    }
}

- (NSArray*)targets;
{
    return [NSArray arrayWithArray:targets];
}

- (void)addTarget:(id<GPUImageInput>)newTarget;
{
    NSInteger nextAvailableTextureIndex = [newTarget nextAvailableTextureIndex];
    [self addTarget:newTarget atTextureLocation:nextAvailableTextureIndex];

    if ([newTarget shouldIgnoreUpdatesToThisTarget])
    {
        _targetToIgnoreForUpdates = newTarget;
    }
}

- (void)addTarget:(id<GPUImageInput>)newTarget atTextureLocation:(NSInteger)textureLocation;
{
    if([targets containsObject:newTarget])
    {
        return;
    }

    cachedMaximumOutputSize = CGSizeZero;
    runSynchronouslyOnVideoProcessingQueue(^{
        [self setInputFramebufferForTarget:newTarget atIndex:textureLocation];
        [targets addObject:newTarget];
        [targetTextureIndices addObject:[NSNumber numberWithInteger:textureLocation]];

        allTargetsWantMonochromeData = allTargetsWantMonochromeData && [newTarget wantsMonochromeInput];
    });
}

- (void)removeTarget:(id<GPUImageInput>)targetToRemove;
{
    if(![targets containsObject:targetToRemove])
    {
        return;
    }

    if (_targetToIgnoreForUpdates == targetToRemove)
    {
        _targetToIgnoreForUpdates = nil;
    }

    cachedMaximumOutputSize = CGSizeZero;

    NSInteger indexOfObject = [targets indexOfObject:targetToRemove];
    NSInteger textureIndexOfTarget = [[targetTextureIndices objectAtIndex:indexOfObject] integerValue];

    runSynchronouslyOnVideoProcessingQueue(^{
        [targetToRemove setInputSize:CGSizeZero atIndex:textureIndexOfTarget];
        [targetToRemove setInputRotation:kGPUImageNoRotation atIndex:textureIndexOfTarget];

        [targetTextureIndices removeObjectAtIndex:indexOfObject];
        [targets removeObject:targetToRemove];
        [targetToRemove endProcessing];
    });
}

- (void)removeAllTargets;
{
    cachedMaximumOutputSize = CGSizeZero;
    runSynchronouslyOnVideoProcessingQueue(^{
        for (id<GPUImageInput> targetToRemove in targets)
        {
            NSInteger indexOfObject = [targets indexOfObject:targetToRemove];
            NSInteger textureIndexOfTarget = [[targetTextureIndices objectAtIndex:indexOfObject] integerValue];

            [targetToRemove setInputSize:CGSizeZero atIndex:textureIndexOfTarget];
            [targetToRemove setInputRotation:kGPUImageNoRotation atIndex:textureIndexOfTarget];
        }
        [targets removeAllObjects];
        [targetTextureIndices removeAllObjects];

        allTargetsWantMonochromeData = YES;
    });
}

• 提取图像。包含了提取得到 CGImage 和 UIImage 以下代码只是 支持iOS设备的代码, MAC代码未指出

#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE

//依据设备的方向生成当前帧的图片
- (UIImage *)imageFromCurrentFramebuffer;
{
    UIDeviceOrientation deviceOrientation = [[UIDevice currentDevice] orientation];
    UIImageOrientation imageOrientation = UIImageOrientationLeft;
    switch (deviceOrientation)
    {
        case UIDeviceOrientationPortrait:
            imageOrientation = UIImageOrientationUp;
            break;
        case UIDeviceOrientationPortraitUpsideDown:
            imageOrientation = UIImageOrientationDown;
            break;
        case UIDeviceOrientationLandscapeLeft:
            imageOrientation = UIImageOrientationLeft;
            break;
        case UIDeviceOrientationLandscapeRight:
            imageOrientation = UIImageOrientationRight;
            break;
        default:
            imageOrientation = UIImageOrientationUp;
            break;
    }

    return [self imageFromCurrentFramebufferWithOrientation:imageOrientation];
}

- (UIImage *)imageFromCurrentFramebufferWithOrientation:(UIImageOrientation)imageOrientation;
{
    CGImageRef cgImageFromBytes = [self newCGImageFromCurrentlyProcessedOutput];
    UIImage *finalImage = [UIImage imageWithCGImage:cgImageFromBytes scale:1.0 orientation:imageOrientation];
    CGImageRelease(cgImageFromBytes);

    return finalImage;
}

- (UIImage *)imageByFilteringImage:(UIImage *)imageToFilter;
{
    CGImageRef image = [self newCGImageByFilteringCGImage:[imageToFilter CGImage]];
    UIImage *processedImage = [UIImage imageWithCGImage:image scale:[imageToFilter scale] orientation:[imageToFilter imageOrientation]];
    CGImageRelease(image);
    return processedImage;
}

- (CGImageRef)newCGImageByFilteringImage:(UIImage *)imageToFilter
{
    return [self newCGImageByFilteringCGImage:[imageToFilter CGImage]];
}