GPUImage API文档之GPUImageFramebuffer类

　　GPUImageFramebuffer类用于管理帧缓冲对象，负责帧缓冲对象的创建和销毁，读取帧缓冲内容

　　属性

　　@property(readonly) CGSize size

　　说明：只读属性，在实现中，设置缓冲区的size

 

　　@property(readonly) GPUTextureOptions textureOptions

　　说明：纹理的选项

 

　　@property(readonly) GLuint texture

　　说明：管理纹理

 

　　@property(readonly) BOOL missingFramebuffer

　　说明：指示是否丢失帧缓冲对象

　　

　　方法

　　　- (id)initWithSize:(CGSize)framebufferSize

　　　　说明：创建一个size为framebufferSize大小的帧缓冲对象

　　　　参数：framebuffer的size。

　　　　返回：创建成功的帧缓冲对象。

　　　　实现

- (id)initWithSize:(CGSize)framebufferSize;
{
    GPUTextureOptions defaultTextureOptions;
    defaultTextureOptions.minFilter = GL_LINEAR;
    defaultTextureOptions.magFilter = GL_LINEAR;
    defaultTextureOptions.wrapS = GL_CLAMP_TO_EDGE;
    defaultTextureOptions.wrapT = GL_CLAMP_TO_EDGE;
    defaultTextureOptions.internalFormat = GL_RGBA;
    defaultTextureOptions.format = GL_BGRA;
    defaultTextureOptions.type = GL_UNSIGNED_BYTE;

    if (!(self = [self initWithSize:framebufferSize textureOptions:defaultTextureOptions onlyTexture:NO]))
    {
        return nil;
    }

    return self;
}

 

　　   - (id)initWithSize:(CGSize)framebufferSize textureOptions:(GPUTextureOptions)fboTextureOptions onlyTexture:(BOOL)onlyGenerateTexture

　　　　说明：创建一个size为framebufferSize大小的帧缓冲对象

　　　　参数：framebufferSize为framebuffer的size。fboTextureOptions是纹理的详细配置。onlyGenerateTexture说明是否只创建纹理而不创建陈帧缓冲对象。

　　　　返回：创建成功的帧缓冲对象。

　　　　实现

- (id)initWithSize:(CGSize)framebufferSize textureOptions:(GPUTextureOptions)fboTextureOptions onlyTexture:(BOOL)onlyGenerateTexture;
{
    if (!(self = [super init]))
    {
        return nil;
    }
    
    _textureOptions = fboTextureOptions;
    _size = framebufferSize;
    framebufferReferenceCount = 0;
    referenceCountingDisabled = NO;
    _missingFramebuffer = onlyGenerateTexture;

    if (_missingFramebuffer)
    {
        runSynchronouslyOnVideoProcessingQueue(^{
            [GPUImageContext useImageProcessingContext];
            [self generateTexture];
            framebuffer = 0;
        });
    }
    else
    {
        [self generateFramebuffer];
    }
    return self;
}

 

　　　- (id)initWithSize:(CGSize)framebufferSize overriddenTexture:(GLuint)inputTexture

　　　　说明：创建一个size为framebufferSize大小的帧缓冲对象

　　　　参数：inputTexture为输入的纹理，用于渲染图片。

　　　　返回：创建成功的帧缓冲对象。

　　　　实现

- (id)initWithSize:(CGSize)framebufferSize overriddenTexture:(GLuint)inputTexture;
{
    if (!(self = [super init]))
    {
        return nil;
    }

    GPUTextureOptions defaultTextureOptions;
    defaultTextureOptions.minFilter = GL_LINEAR;
    defaultTextureOptions.magFilter = GL_LINEAR;
    defaultTextureOptions.wrapS = GL_CLAMP_TO_EDGE;
    defaultTextureOptions.wrapT = GL_CLAMP_TO_EDGE;
    defaultTextureOptions.internalFormat = GL_RGBA;
    defaultTextureOptions.format = GL_BGRA;
    defaultTextureOptions.type = GL_UNSIGNED_BYTE;

    _textureOptions = defaultTextureOptions;
    _size = framebufferSize;
    framebufferReferenceCount = 0;
    referenceCountingDisabled = YES;
    
    _texture = inputTexture;
    
    return self;
}

 

　　　- (void)activateFramebuffer

　　　　说明：激活刚创建的framebuffer对象。只有调用它后，才会起作用。

　　　　实现　

- (void)activateFramebuffer;
{
    glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
    glViewport(0, 0, (int)_size.width, (int)_size.height);
}

 

　　　- (void)lock

　　　　说明：引用计数管理 +1

　　　　实现

- (void)lock;
{
    if (referenceCountingDisabled)
    {
        return;
    }
    
    framebufferReferenceCount++;
}

 

　　　- (void)unlock

　　　　说明：引用计数管理 -1

　　　　实现

- (void)unlock;
{
    if (referenceCountingDisabled)
    {
        return;
    }

    NSAssert(framebufferReferenceCount > 0, @"Tried to overrelease a framebuffer, did you forget to call -useNextFrameForImageCapture before using -imageFromCurrentFramebuffer?");
    framebufferReferenceCount--;
    if (framebufferReferenceCount < 1)
    {
        [[GPUImageContext sharedFramebufferCache] returnFramebufferToCache:self];
    }
}

 

　　　- (void)clearAllLocks

　　　　说明：引用计数管理 设置为0

　　　　实现

- (void)clearAllLocks;
{
    framebufferReferenceCount = 0;
}

 

　　　- (void)disableReferenceCounting

　　　　说明：引用计数管理 禁用引用计数

　　　　实现

- (void)disableReferenceCounting;
{
    referenceCountingDisabled = YES;
}

 

　　　- (void)enableReferenceCounting

　　　　说明：引用计数管理 启用引用计数

　　　　实现

- (void)enableReferenceCounting;
{
    referenceCountingDisabled = NO;
}

 

　　　- (CGImageRef)newCGImageFromFramebufferContents

　　　　说明：输出帧缓冲内容。【说明待更新......】

　　　　实现

- (CGImageRef)newCGImageFromFramebufferContents;
{
    // a CGImage can only be created from a 'normal' color texture
    NSAssert(self.textureOptions.internalFormat == GL_RGBA, @"For conversion to a CGImage the output texture format for this filter must be GL_RGBA.");
    NSAssert(self.textureOptions.type == GL_UNSIGNED_BYTE, @"For conversion to a CGImage the type of the output texture of this filter must be GL_UNSIGNED_BYTE.");
    
    __block CGImageRef cgImageFromBytes;
    
    runSynchronouslyOnVideoProcessingQueue(^{
        [GPUImageContext useImageProcessingContext];
        
        NSUInteger totalBytesForImage = (int)_size.width * (int)_size.height * 4;
        // It appears that the width of a texture must be padded out to be a multiple of 8 (32 bytes) if reading from it using a texture cache
        
        GLubyte *rawImagePixels;
        
        CGDataProviderRef dataProvider = NULL;
        if ([GPUImageContext supportsFastTextureUpload])
        {
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
            NSUInteger paddedWidthOfImage = CVPixelBufferGetBytesPerRow(renderTarget) / 4.0;
            NSUInteger paddedBytesForImage = paddedWidthOfImage * (int)_size.height * 4;
            
            glFinish();
            CFRetain(renderTarget); // I need to retain the pixel buffer here and release in the data source callback to prevent its bytes from being prematurely deallocated during a photo write operation
            [self lockForReading];
            rawImagePixels = (GLubyte *)CVPixelBufferGetBaseAddress(renderTarget);
            dataProvider = CGDataProviderCreateWithData((__bridge_retained void*)self, rawImagePixels, paddedBytesForImage, dataProviderUnlockCallback);
            [[GPUImageContext sharedFramebufferCache] addFramebufferToActiveImageCaptureList:self]; // In case the framebuffer is swapped out on the filter, need to have a strong reference to it somewhere for it to hang on while the image is in existence
#else
#endif
        }
        else
        {
            [self activateFramebuffer];
            rawImagePixels = (GLubyte *)malloc(totalBytesForImage);
            glReadPixels(0, 0, (int)_size.width, (int)_size.height, GL_RGBA, GL_UNSIGNED_BYTE, rawImagePixels);
            dataProvider = CGDataProviderCreateWithData(NULL, rawImagePixels, totalBytesForImage, dataProviderReleaseCallback);
            [self unlock]; // Don't need to keep this around anymore
        }
        
        CGColorSpaceRef defaultRGBColorSpace = CGColorSpaceCreateDeviceRGB();
        
        if ([GPUImageContext supportsFastTextureUpload])
        {
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
            cgImageFromBytes = CGImageCreate((int)_size.width, (int)_size.height, 8, 32, CVPixelBufferGetBytesPerRow(renderTarget), defaultRGBColorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst, dataProvider, NULL, NO, kCGRenderingIntentDefault);
#else
#endif
        }
        else
        {
            cgImageFromBytes = CGImageCreate((int)_size.width, (int)_size.height, 8, 32, 4 * (int)_size.width, defaultRGBColorSpace, kCGBitmapByteOrderDefault | kCGImageAlphaLast, dataProvider, NULL, NO, kCGRenderingIntentDefault);
        }
        
        // Capture image with current device orientation
        CGDataProviderRelease(dataProvider);
        CGColorSpaceRelease(defaultRGBColorSpace);
        
    });
    
    return cgImageFromBytes;
}

 

　　　- (void)restoreRenderTarget

　　　　说明：还原渲染目标对象

　　　　实现

- (void)restoreRenderTarget;
{
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
    [self unlockAfterReading];
    CFRelease(renderTarget);
#else
#endif
}

 

　　　- (void)lockForReading

　　　　说明：锁定PixelBuffer

　　　　实现：

- (void)lockForReading
{
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
    if ([GPUImageContext supportsFastTextureUpload])
    {
        if (readLockCount == 0)
        {
            CVPixelBufferLockBaseAddress(renderTarget, 0);
        }
        readLockCount++;
    }
#endif
}

 

 

　　　- (void)unlockAfterReading

　　　　说明：解锁PixelBuffer

- (void)unlockAfterReading
{
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
    if ([GPUImageContext supportsFastTextureUpload])
    {
        NSAssert(readLockCount > 0, @"Unbalanced call to -[GPUImageFramebuffer unlockAfterReading]");
        readLockCount--;
        if (readLockCount == 0)
        {
            CVPixelBufferUnlockBaseAddress(renderTarget, 0);
        }
    }
#endif
}

 

　　　- (NSUInteger)bytesPerRow

　　　　说明：获取pixel buffer的行字节数

　　　　实现

- (NSUInteger)bytesPerRow;
{
    if ([GPUImageContext supportsFastTextureUpload])
    {
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
        return CVPixelBufferGetBytesPerRow(renderTarget);
#else
        return _size.width * 4; // TODO: do more with this on the non-texture-cache side
#endif
    }
    else
    {
        return _size.width * 4;
    }
}

 

　　　- (GLubyte *)byteBuffer

　　　　说明：获取pixel buffer的基地址

　　　　实现

- (GLubyte *)byteBuffer;
{
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
    [self lockForReading];
    GLubyte * bufferBytes = CVPixelBufferGetBaseAddress(renderTarget);
    [self unlockAfterReading];
    return bufferBytes;
#else
    return NULL; // TODO: do more with this on the non-texture-cache side
#endif
}

 

完整代码

#import <Foundation/Foundation.h>

#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
#import <OpenGLES/EAGL.h>
#import <OpenGLES/ES2/gl.h>
#import <OpenGLES/ES2/glext.h>
#else
#import <OpenGL/OpenGL.h>
#import <OpenGL/gl.h>
#endif

#import <QuartzCore/QuartzCore.h>
#import <CoreMedia/CoreMedia.h>


typedef struct GPUTextureOptions {
    GLenum minFilter;
    GLenum magFilter;
    GLenum wrapS;
    GLenum wrapT;
    GLenum internalFormat;
    GLenum format;
    GLenum type;
} GPUTextureOptions;

@interface GPUImageFramebuffer : NSObject

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

// Initialization and teardown
- (id)initWithSize:(CGSize)framebufferSize;
- (id)initWithSize:(CGSize)framebufferSize textureOptions:(GPUTextureOptions)fboTextureOptions onlyTexture:(BOOL)onlyGenerateTexture;
- (id)initWithSize:(CGSize)framebufferSize overriddenTexture:(GLuint)inputTexture;

// Usage
- (void)activateFramebuffer;

// Reference counting
- (void)lock;
- (void)unlock;
- (void)clearAllLocks;
- (void)disableReferenceCounting;
- (void)enableReferenceCounting;

// Image capture
- (CGImageRef)newCGImageFromFramebufferContents;
- (void)restoreRenderTarget;

// Raw data bytes
- (void)lockForReading;
- (void)unlockAfterReading;
- (NSUInteger)bytesPerRow;
- (GLubyte *)byteBuffer;

@end

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