版本記錄

前言

GPUImage是直接利用顯卡實現(xiàn)視頻或者圖像處理的技術(shù)。感興趣可以看上面幾篇文章弥咪。
1. GPUImage解析（一） —— 基本概覽（一）
2. GPUImage解析（二） —— 基本概覽（二）
3. GPUImage解析（三） —— 基本概覽（三）
4. GPUImage解析（四） —— 安裝方法及框架介紹

框架中的幾個基類

該框架其實可以分為兩個部分肋坚，一部分就是基類百新，另外一部分就是濾鏡昭抒，這一篇我們就說一下這個框架的基類部分危彩。

// Base classes

#import "GPUImageContext.h"
#import "GPUImageOutput.h"
#import "GPUImageView.h"
#import "GPUImageVideoCamera.h"
#import "GPUImageStillCamera.h"
#import "GPUImageMovie.h"
#import "GPUImagePicture.h"
#import "GPUImageRawDataInput.h"
#import "GPUImageRawDataOutput.h"
#import "GPUImageMovieWriter.h"
#import "GPUImageFilterPipeline.h"
#import "GPUImageTextureOutput.h"
#import "GPUImageFilterGroup.h"
#import "GPUImageTextureInput.h"
#import "GPUImageUIElement.h"
#import "GPUImageBuffer.h"
#import "GPUImageFramebuffer.h"
#import "GPUImageFramebufferCache.h"

基類詳細(xì)分析

下面我們就詳細(xì)的分析下這幾個基類徒欣。

1. GPUImageContext

• 繼承與屬性

@interface GPUImageContext : NSObject

@property(readonly, nonatomic) dispatch_queue_t contextQueue;
@property(readwrite, retain, nonatomic) GLProgram *currentShaderProgram;
@property(readonly, retain, nonatomic) EAGLContext *context;
@property(readonly) CVOpenGLESTextureCacheRef coreVideoTextureCache;
@property(readonly) GPUImageFramebufferCache *framebufferCache;

• 作用：GPUImageContext是GPUImage對OpenGL ES上下文的封裝逐样，添加了GPUImage相關(guān)的上下文，比如說Program的使用緩存打肝，處理隊列脂新，CV紋理緩存等。

幾個屬性

• contextQueue 統(tǒng)一處理隊列
• currentShaderProgram 正在使用的program
• context OpenGL ES的上下文
• coreVideoTextureCache CV紋理緩存
• framebufferCache GPUImageBuffer緩存
• shaderProgramCache Program的緩存
• shaderProgramUsageHistory Program的使用歷史

幾個方法

• useAsCurrentContext()在useAsCurrentContext設(shè)置當(dāng)前上下文的時候闯睹，會先判斷上下文是否是當(dāng)前context戏羽，不是再設(shè)置（為了避免上下文切換的性能消耗，即使設(shè)置的上下文是同一個上下文也會消耗性能）

• sizeThatFitsWithinATextureForSize()會調(diào)整紋理大小楼吃，如果超過最大的紋理始花，會調(diào)整為不超過最大的紋理寬高。

• (GLProgram*)programForVertexShaderString:fragmentShaderString:
  shaderProgramCache 是program的緩存孩锡，由頂點shader和片元shader字符串拼接起來做key酷宵。

• (void)useSharegroup:(EAGLSharegroup *)sharegroup;
  EAGLSharegroup類管理一個或者多個EAGLContext的OpenGLES資源；這個是一個封閉的類躬窜，沒有開發(fā)者API浇垦。負(fù)責(zé)管理紋理緩存、頂點緩存荣挨、幀緩存男韧、顏色緩存。（textures, buffers, framebuffers, and render buffers）

• (EAGLContext *)context;返回OpenGL ES2.0的上下文默垄，同時設(shè)置glDisable(GL_DEPTH_TEST);此虑，圖像處理管道默認(rèn)不允許使用深度緩存。

2. GPUImageOutput

• 繼承與屬性

/** 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
{
    GPUImageFramebuffer *outputFramebuffer;
    
    NSMutableArray *targets, *targetTextureIndices;
    
    CGSize inputTextureSize, cachedMaximumOutputSize, forcedMaximumSize;
    
    BOOL overrideInputSize;
    
    BOOL allTargetsWantMonochromeData;
    BOOL usingNextFrameForImageCapture;
}

• 作用：GPUImageOutput類將靜態(tài)圖像紋理上傳到OpenGL ES中口锭，然后使用這些紋理去處理進程鏈中的下一個對象朦前。它的子類可以獲得濾鏡處理后的圖片功能。

3. GPUImageView

• 繼承與屬性

/**
 UIView subclass to use as an endpoint for displaying GPUImage outputs
 */
@interface GPUImageView : UIView <GPUImageInput>
{
    GPUImageRotationMode inputRotation;
}

/** The fill mode dictates how images are fit in the view, with the default being kGPUImageFillModePreserveAspectRatio
 */
@property(readwrite, nonatomic) GPUImageFillModeType fillMode;

/** This calculates the current display size, in pixels, taking into account Retina scaling factors
 */
@property(readonly, nonatomic) CGSize sizeInPixels;

@property(nonatomic) BOOL enabled;

/** Handling fill mode
 
 @param redComponent Red component for background color
 @param greenComponent Green component for background color
 @param blueComponent Blue component for background color
 @param alphaComponent Alpha component for background color
 */
- (void)setBackgroundColorRed:(GLfloat)redComponent green:(GLfloat)greenComponent blue:(GLfloat)blueComponent alpha:(GLfloat)alphaComponent;

- (void)setCurrentlyReceivingMonochromeInput:(BOOL)newValue;

@end

• 圖像視圖

4. GPUImageVideoCamera

• 繼承與屬性

/**
 A GPUImageOutput that provides frames from either camera
*/
@interface GPUImageVideoCamera : GPUImageOutput <AVCaptureVideoDataOutputSampleBufferDelegate, AVCaptureAudioDataOutputSampleBufferDelegate>
{
    NSUInteger numberOfFramesCaptured;
    CGFloat totalFrameTimeDuringCapture;
    
    AVCaptureSession *_captureSession;
    AVCaptureDevice *_inputCamera;
    AVCaptureDevice *_microphone;
    AVCaptureDeviceInput *videoInput;
    AVCaptureVideoDataOutput *videoOutput;

    BOOL capturePaused;
    GPUImageRotationMode outputRotation, internalRotation;
    dispatch_semaphore_t frameRenderingSemaphore;
        
    BOOL captureAsYUV;
    GLuint luminanceTexture, chrominanceTexture;

    __unsafe_unretained id<GPUImageVideoCameraDelegate> _delegate;
}

/// The AVCaptureSession used to capture from the camera
@property(readonly, retain, nonatomic) AVCaptureSession *captureSession;

/// This enables the capture session preset to be changed on the fly
@property (readwrite, nonatomic, copy) NSString *captureSessionPreset;

/// This sets the frame rate of the camera (iOS 5 and above only)
/**
 Setting this to 0 or below will set the frame rate back to the default setting for a particular preset.
 */
@property (readwrite) int32_t frameRate;

/// Easy way to tell which cameras are present on device
@property (readonly, getter = isFrontFacingCameraPresent) BOOL frontFacingCameraPresent;
@property (readonly, getter = isBackFacingCameraPresent) BOOL backFacingCameraPresent;

/// This enables the benchmarking mode, which logs out instantaneous and average frame times to the console
@property(readwrite, nonatomic) BOOL runBenchmark;

/// Use this property to manage camera settings. Focus point, exposure point, etc.
@property(readonly) AVCaptureDevice *inputCamera;

/// This determines the rotation applied to the output image, based on the source material
@property(readwrite, nonatomic) UIInterfaceOrientation outputImageOrientation;

/// These properties determine whether or not the two camera orientations should be mirrored. By default, both are NO.
@property(readwrite, nonatomic) BOOL horizontallyMirrorFrontFacingCamera, horizontallyMirrorRearFacingCamera;

@property(nonatomic, assign) id<GPUImageVideoCameraDelegate> delegate;

• 作用：GPUImageVideoCamera是GPUImageOutput的子類鹃操，提供來自攝像頭的圖像數(shù)據(jù)作為源數(shù)據(jù)韭寸，一般是響應(yīng)鏈的源頭。GPUImage使用AVFoundation框架來獲取視頻荆隘。
  AVCaptureSession類從AV輸入設(shè)備的采集數(shù)據(jù)到制定的輸出恩伺。為了實現(xiàn)實時的圖像捕獲，要實現(xiàn)AVCaptureSession類臭胜，添加合適的輸入（AVCaptureDeviceInput）和輸出（比如 AVCaptureMovieFileOutput）調(diào)用startRunning開始輸入到輸出的數(shù)據(jù)流莫其，調(diào)用stopRunning停止數(shù)據(jù)流癞尚。需要注意的是startRunning函數(shù)會花費一定的時間，所以不能在主線程（UI線程）調(diào)用乱陡，防止卡頓浇揩。

5. GPUImageStillCamera

• 繼承與屬性

@interface GPUImageStillCamera : GPUImageVideoCamera

/** The JPEG compression quality to use when capturing a photo as a JPEG.
 */
@property CGFloat jpegCompressionQuality;

// Only reliably set inside the context of the completion handler of one of the capture methods
@property (readonly) NSDictionary *currentCaptureMetadata;

• 作用：GPUImage中GPUImageStillCamera可以調(diào)用系統(tǒng)相機，并實現(xiàn)實時濾鏡憨颠，GPUImageStillCamera繼承自GPUImageVideoCamera類胳徽，添加了捕獲照片的功能。

使用步驟

• 創(chuàng)建預(yù)覽View 即必須的GPUImageView
• 創(chuàng)建濾鏡
• 創(chuàng)建Camera 即我們要用到的GPUImageStillCamera
• addTarget 并開始處理startCameraCapture
• 回調(diào)數(shù)據(jù)爽彤、寫入相冊

6. GPUImageMovie

• 繼承與屬性

/** Source object for filtering movies
 */
@interface GPUImageMovie : GPUImageOutput

@property (readwrite, retain) AVAsset *asset;
@property (readwrite, retain) AVPlayerItem *playerItem;
@property(readwrite, retain) NSURL *url;

/** This enables the benchmarking mode, which logs out instantaneous and average frame times to the console
 */
@property(readwrite, nonatomic) BOOL runBenchmark;

/** This determines whether to play back a movie as fast as the frames can be processed, or if the original speed of the movie should be respected. Defaults to NO.
 */
@property(readwrite, nonatomic) BOOL playAtActualSpeed;

/** This determines whether the video should repeat (loop) at the end and restart from the beginning. Defaults to NO.
 */
@property(readwrite, nonatomic) BOOL shouldRepeat;

/** This specifies the progress of the process on a scale from 0 to 1.0. A value of 0 means the process has not yet begun, A value of 1.0 means the conversaion is complete.
    This property is not key-value observable.
 */
@property(readonly, nonatomic) float progress;

/** This is used to send the delete Movie did complete playing alert
 */
@property (readwrite, nonatomic, assign) id <GPUImageMovieDelegate>delegate;

@property (readonly, nonatomic) AVAssetReader *assetReader;
@property (readonly, nonatomic) BOOL audioEncodingIsFinished;
@property (readonly, nonatomic) BOOL videoEncodingIsFinished;

• 作用：GPUImageMovie類繼承了GPUImageOutput類养盗，一般作為響應(yīng)鏈的源頭，可以通過url适篙、playerItem往核、asset初始化。

7. GPUImagePicture

• 繼承與屬性

@interface GPUImagePicture : GPUImageOutput
{
    CGSize pixelSizeOfImage;
    BOOL hasProcessedImage;
    
    dispatch_semaphore_t imageUpdateSemaphore;
}

• 作用：GPUImagePicture是PGUImage的圖像處理類嚷节，繼承GPUImageOutput聂儒，一般作為響應(yīng)鏈的源頭。

幾個屬性

• pixelSizeOfImage 圖像的像素大小硫痰。
• hasProcessedImage 圖像是否已處理衩婚。
• imageUpdateSemaphore圖像處理的GCD信號量。

幾個方法

• - (id)initWithCGImage:smoothlyScaleOutput:用源圖像newImageSource和是否采用mipmaps來初始化GPUImagePicture效斑。
  如果圖像大小超過OpenGL ES最大紋理寬高非春，或者使用mipmaps，或者圖像數(shù)據(jù)是浮點型缓屠、顏色空間不對等都會采用CoreGraphics重新繪制圖像奇昙。
  然后通過glTexImage2D把圖像數(shù)據(jù)發(fā)送給GPU，最后釋放掉CPU的圖像數(shù)據(jù)敌完。
• - (BOOL)processImageWithCompletionHandler:;通知targets處理圖像敬矩，并在完成后調(diào)用complete代碼塊。在處理開始時蠢挡，會標(biāo)記hasProcessedImage為YES，并調(diào)用dispatch_semaphore_wait()凳忙，確定上次處理已經(jīng)完成业踏，否則取消這次處理。
• - (void)addTarget: atTextureLocation:;添加target到響應(yīng)鏈涧卵。如果hasProcessedImage為YES勤家，表示圖像已經(jīng)處理完畢，直接設(shè)置targets的InputSize柳恐，并調(diào)用newFrameReadyAtTime()通知target伐脖。

8. GPUImageRawDataInput

• 繼承與屬性

@interface GPUImageRawDataInput : GPUImageOutput
{
    CGSize uploadedImageSize;
    
    dispatch_semaphore_t dataUpdateSemaphore;
}

• 作用：GPUImageRawDataInput類繼承GPUImageOutput類热幔，可以接受二進制數(shù)據(jù)，按照特定的顏色格式讼庇，把數(shù)據(jù)轉(zhuǎn)成圖像并傳入響應(yīng)鏈绎巨；GPUImageRawDataInput不會對傳入的數(shù)據(jù)copied或者retained，但你不需要在使用完之后去釋放蠕啄；二進制數(shù)據(jù)發(fā)送到GPU的紋理單元场勤，默認(rèn)的顏色格式是BGRA和整型數(shù)據(jù)。

  • 上傳圖片的邏輯：先申請outputframebuffer 歼跟，然后綁定紋理和媳，最后用glTexImage2D 上傳圖像數(shù)據(jù)到GPU。
  • processData方法：處理圖片哈街；如果上一次操作還未完成留瞳，則直接返回。

9. GPUImageRawDataOutput

• 繼承與屬性

#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
@interface GPUImageRawDataOutput : NSObject <GPUImageInput> {
    CGSize imageSize;
    GPUImageRotationMode inputRotation;
    BOOL outputBGRA;
}
#else
@interface GPUImageRawDataOutput : NSObject <GPUImageInput> {
    CGSize imageSize;
    GPUImageRotationMode inputRotation;
    BOOL outputBGRA;
}
#endif

@property(readonly) GLubyte *rawBytesForImage;
@property(nonatomic, copy) void(^newFrameAvailableBlock)(void);
@property(nonatomic) BOOL enabled;

• 作用：GPUImageRawDataOutput類實現(xiàn)協(xié)議GPUImageInput骚秦，可以接受響應(yīng)鏈的圖像信息她倘，并且以二進制的格式返回數(shù)據(jù)；

  • rawBytesForImage屬性： 二進制數(shù)據(jù)的指針骤竹；
  • GPUByteColorVector結(jié)構(gòu)體：RGBA顏色空間結(jié)構(gòu)體帝牡，便于讀取二進制數(shù)據(jù)；
  • supportsFastTextureUpload用的BGRA的顏色格式蒙揣；
    如果需要輸出RGBA靶溜，則可以對BGRA格式再做一次RGBA->BRGA的顏色轉(zhuǎn)換；RGBA -> BGRA 的操作如下：
    texture2D(inputImageTexture, textureCoordinate).bgra;
  • lockNextFramebuffer屬性：標(biāo)志是否要讀取圖像信息如果為YES懒震，會調(diào)用CVPixelBufferLockBaseAddress鎖住對應(yīng)的CVPixelBufferRef罩息；

10. GPUImageMovieWriter

• 繼承與屬性

@interface GPUImageMovieWriter : NSObject <GPUImageInput>
{
    BOOL alreadyFinishedRecording;
    
    NSURL *movieURL;
    NSString *fileType;
    AVAssetWriter *assetWriter;
    AVAssetWriterInput *assetWriterAudioInput;
    AVAssetWriterInput *assetWriterVideoInput;
    AVAssetWriterInputPixelBufferAdaptor *assetWriterPixelBufferInput;
    
    GPUImageContext *_movieWriterContext;
    CVPixelBufferRef renderTarget;
    CVOpenGLESTextureRef renderTexture;

    CGSize videoSize;
    GPUImageRotationMode inputRotation;
}

@property(readwrite, nonatomic) BOOL hasAudioTrack;
@property(readwrite, nonatomic) BOOL shouldPassthroughAudio;
@property(readwrite, nonatomic) BOOL shouldInvalidateAudioSampleWhenDone;
@property(nonatomic, copy) void(^completionBlock)(void);
@property(nonatomic, copy) void(^failureBlock)(NSError*);
@property(nonatomic, assign) id<GPUImageMovieWriterDelegate> delegate;
@property(readwrite, nonatomic) BOOL encodingLiveVideo;
@property(nonatomic, copy) BOOL(^videoInputReadyCallback)(void);
@property(nonatomic, copy) BOOL(^audioInputReadyCallback)(void);
@property(nonatomic, copy) void(^audioProcessingCallback)(SInt16 **samplesRef, CMItemCount numSamplesInBuffer);
@property(nonatomic) BOOL enabled;
@property(nonatomic, readonly) AVAssetWriter *assetWriter;
@property(nonatomic, readonly) CMTime duration;
@property(nonatomic, assign) CGAffineTransform transform;
@property(nonatomic, copy) NSArray *metaData;
@property(nonatomic, assign, getter = isPaused) BOOL paused;
@property(nonatomic, retain) GPUImageContext *movieWriterContext;

• 作用：GPUImageMovieWriter類實現(xiàn)GPUImageInput協(xié)議，一般作為響應(yīng)鏈的終點个扰。shouldPassthroughAudio表示是否使用源音源瓷炮。
  movieFile.audioEncodingTarget = movieWriter;表示音頻來源是文件

11. GPUImageFilterPipeline

• 繼承與屬性

@interface GPUImageFilterPipeline : NSObject
{
    NSString *stringValue;
}

@property (strong) NSMutableArray *filters;

@property (strong) GPUImageOutput *input;
@property (strong) id <GPUImageInput> output;

• 作用：GPUImageFilterPipeline類是濾鏡通道，把inputs的濾鏡組合起來递宅，然后添加output為最后的輸出目標(biāo)娘香。

  • filters為輸入的濾鏡，output為輸出目標(biāo)办龄；
  • 把filters的濾鏡按照鏈表的形式串聯(lián)起來烘绽。

12. GPUImageTextureOutput

• 繼承與屬性

@interface GPUImageTextureOutput : NSObject <GPUImageInput>
{
    GPUImageFramebuffer *firstInputFramebuffer;
}

@property(readwrite, unsafe_unretained, nonatomic) id<GPUImageTextureOutputDelegate> delegate;
@property(readonly) GLuint texture;
@property(nonatomic) BOOL enabled;

• 作用：GPUImageTextureOutput類實現(xiàn)GPUImageInput協(xié)議，可以接受響應(yīng)鏈的圖像俐填，并返回對應(yīng)的OpenGL ES紋理安接。

• delegate屬性：實現(xiàn)了GPUImageTextureOutputDelegate協(xié)議的回調(diào)對象；

• texture屬性：OpenGL ES的紋理英融，只讀盏檐；

• enabled屬性：是否有效歇式，默認(rèn)為有效；

• doneWithTexture方法：結(jié)束處理紋理圖像胡野，解鎖firstInputFramebuffer材失。

13. GPUImageFilterGroup

• 繼承與屬性

@interface GPUImageFilterGroup : GPUImageOutput <GPUImageInput>
{
    NSMutableArray *filters;
    BOOL isEndProcessing;
}

@property(readwrite, nonatomic, strong) GPUImageOutput<GPUImageInput> *terminalFilter;
@property(readwrite, nonatomic, strong) NSArray *initialFilters;
@property(readwrite, nonatomic, strong) GPUImageOutput<GPUImageInput> *inputFilterToIgnoreForUpdates; 

• 作用：組合濾鏡，添加濾鏡的順序不同给涕，效果也不同豺憔。

14. GPUImageTextureInput

• 繼承與屬性

@interface GPUImageTextureInput : GPUImageOutput
{
    CGSize textureSize;
}

// Initialization and teardown
- (id)initWithTexture:(GLuint)newInputTexture size:(CGSize)newTextureSize;

// Image rendering
- (void)processTextureWithFrameTime:(CMTime)frameTime;

@end

• 作用：GPUImageTextureInput類繼承GPUImageOutput類，可以作為響應(yīng)鏈的起點够庙，把OpenGL ES紋理對應(yīng)的紋理信息導(dǎo)入響應(yīng)鏈處理恭应。textureSize屬性為紋理尺寸；
  初始化的時候耘眨，分配一個GPUImageFramebuffer昼榛，緩存紋理單元的信息；process的時候直接調(diào)用targets對應(yīng)的就緒方法剔难，因為圖像信息就在OpenGL ES控制內(nèi)存中胆屿。

GPUImageTextureOutput和 GPUImageTextureInput用于 向OpenGL ES 輸入或者輸出紋理，把GPUImage的輸出作為OpenGL ES的紋理或者把OpenGL ES的輸出作為GPUImage的紋理輸入偶宫。

15. GPUImageUIElement

• 繼承與屬性

@interface GPUImageUIElement : GPUImageOutput

// Initialization and teardown
- (id)initWithView:(UIView *)inputView;
- (id)initWithLayer:(CALayer *)inputLayer;

// Layer management
- (CGSize)layerSizeInPixels;
- (void)update;
- (void)updateUsingCurrentTime;
- (void)updateWithTimestamp:(CMTime)frameTime;

@end

• 作用：GPUImageUIElement繼承GPUImageOutput類非迹，作為響應(yīng)鏈的源頭。通過CoreGraphics把UIView渲染到圖像纯趋，并通過glTexImage2D綁定到outputFramebuffer指定的紋理憎兽，最后通知targets紋理就緒。

16. GPUImageBuffer

• 繼承與屬性

@interface GPUImageBuffer : GPUImageFilter
{
    NSMutableArray *bufferedFramebuffers;
}

@property(readwrite, nonatomic) NSUInteger bufferSize;

@end

17. GPUImageFramebuffer

• 繼承與屬性

@interface GPUImageFramebuffer : NSObject

@property(readonly) CGSize size;
@property(readonly) GPUTextureOptions textureOptions;
@property(readonly) GLuint texture;
@property(readonly) BOOL missingFramebuffer;

• 作用：假設(shè)我們自定義一個OpenGL ES程序來處理圖片吵冒，那么會有以下幾個步驟：
  • 初始化OpenGL ES環(huán)境纯命，編譯、鏈接頂點著色器和片元著色器痹栖；
  • 緩存頂點亿汞、紋理坐標(biāo)數(shù)據(jù)，傳送圖像數(shù)據(jù)到GPU揪阿；
  • 繪制圖元到特定的幀緩存疗我；
  • 在幀緩存取出繪制的圖像。
    GPUImageFilter負(fù)責(zé)的是第一南捂、二碍粥、三步。
    GPUImageFramebuffer負(fù)責(zé)是第四步黑毅。

18. GPUImageFramebufferCache

• 繼承與屬性

@interface GPUImageFramebufferCache : NSObject

// Framebuffer management
- (GPUImageFramebuffer *)fetchFramebufferForSize:(CGSize)framebufferSize textureOptions:(GPUTextureOptions)textureOptions onlyTexture:(BOOL)onlyTexture;
- (GPUImageFramebuffer *)fetchFramebufferForSize:(CGSize)framebufferSize onlyTexture:(BOOL)onlyTexture;
- (void)returnFramebufferToCache:(GPUImageFramebuffer *)framebuffer;
- (void)purgeAllUnassignedFramebuffers;
- (void)addFramebufferToActiveImageCaptureList:(GPUImageFramebuffer *)framebuffer;
- (void)removeFramebufferFromActiveImageCaptureList:(GPUImageFramebuffer *)framebuffer;

@end

• 作用：GPUImageFramebufferCache是GPUImageFrameBuffer的管理類。

幾個屬性

• CacheframebufferCache緩存字典
• framebufferTypeCounts 緩存數(shù)量字典
• activeImageCaptureList 正在讀取Image數(shù)據(jù)的
• GPUImageFrameBuffer列表
• framebufferCacheQueue 緩存隊列

幾個方法

• - (NSString *)hashForSize: textureOptions:onlyTexture:;
  根據(jù)size钦讳、textureOptions和onlyTexture矿瘦，創(chuàng)建緩存字符串枕面。
  緩存字符串+當(dāng)前緩存數(shù)量形成framebufferCache緩存的key。
  如果找不到framebufferCache對應(yīng)的數(shù)量缚去，會創(chuàng)建新的緩存潮秘。

• - (void)returnFramebufferToCache:;回收緩存。根據(jù)size易结、textureOptions和onlyTexture枕荞，創(chuàng)建緩存字符串，緩存字符串+當(dāng)前緩存數(shù)量形成framebufferCache緩存的key搞动。（之所以會加上數(shù)量躏精，是因為緩存字符串不唯一）

• - (void)addFramebufferToActiveImageCaptureList:;
-(void)removeFramebufferFromActiveImageCaptureList:
  這兩個方法主要用于，當(dāng)newCGImageFromFramebufferContents()讀取幀緩存圖像數(shù)據(jù)時鹦肿，保持GPUImageFramebuffer的引用矗烛。并且讀取完數(shù)據(jù)后，在dataProviderUnlockCallback()方法釋放箩溃。

參考文章

1. GPUImage詳細(xì)解析（九）圖像的輸入輸出和濾鏡通道
2. GPUImageStillCamera 攝像頭-照相
3. iOS GPUImage研究總結(jié)

后記

未完瞭吃，待續(xù)~~~