GPUImage源码解读(十五)_gpuimagerawdatainput bgra-优快云博客

GPUImageRawDataOutput

GPUImageRawDataOutput实现了GPUImageInput协议，它可以将输入的帧缓存转换为原始数据。

构造方法。构造方法最主要的任务是构造GL程序。

- (id)initWithImageSize:(CGSize)newImageSize resultsInBGRAFormat:(BOOL)resultsInBGRAFormat;

初始化的时候需要指定纹理大小以及是否以BGRA形式的数据输入。如果是以BGRA的形式输入，则在选择片段着色器的时候会选择kGPUImageColorSwizzlingFragmentShaderString着色器来进行从BGRA-到RGBA的转换。


- (id)initWithImageSize:(CGSize)newImageSize resultsInBGRAFormat:(BOOL)resultsInBGRAFormat;
{
    if (!(self = [super init]))
    {
        return nil;
    }

    self.enabled = YES;
    lockNextFramebuffer = NO;
    outputBGRA = resultsInBGRAFormat;
    imageSize = newImageSize;
    hasReadFromTheCurrentFrame = NO;
    _rawBytesForImage = NULL;
    inputRotation = kGPUImageNoRotation;

    [GPUImageContext useImageProcessingContext];
     // 如果使用了BGRA ，则选择kGPUImageColorSwizzlingFragmentShaderString着色器
    if ( (outputBGRA && ![GPUImageContext supportsFastTextureUpload]) || (!outputBGRA && [GPUImageContext supportsFastTextureUpload]) )
    {
        dataProgram = [[GPUImageContext sharedImageProcessingContext] programForVertexShaderString:kGPUImageVertexShaderString fragmentShaderString:kGPUImageColorSwizzlingFragmentShaderString];
    }
     // 否则选用kGPUImagePassthroughFragmentShaderString着色器
    else
    {
        dataProgram = [[GPUImageContext sharedImageProcessingContext] programForVertexShaderString:kGPUImageVertexShaderString fragmentShaderString:kGPUImagePassthroughFragmentShaderString];
    }

    if (!dataProgram.initialized)
    {
        [dataProgram addAttribute:@"position"];
        [dataProgram addAttribute:@"inputTextureCoordinate"];

        if (![dataProgram link])
        {
            NSString *progLog = [dataProgram programLog];
            NSLog(@"Program link log: %@", progLog);
            NSString *fragLog = [dataProgram fragmentShaderLog];
            NSLog(@"Fragment shader compile log: %@", fragLog);
            NSString *vertLog = [dataProgram vertexShaderLog];
            NSLog(@"Vertex shader compile log: %@", vertLog);
            dataProgram = nil;
            NSAssert(NO, @"Filter shader link failed");
        }
    }
     // 获取统一变量和属性
    dataPositionAttribute = [dataProgram attributeIndex:@"position"];
    dataTextureCoordinateAttribute = [dataProgram attributeIndex:@"inputTextureCoordinate"];
    dataInputTextureUniform = [dataProgram uniformIndex:@"inputImageTexture"];

    return self;
}

其他方法

// Data access
// 获取特定位置的像素向量
- (GPUByteColorVector)colorAtLocation:(CGPoint)locationInImage;
// 每行数据大小
- (NSUInteger)bytesPerRowInOutput;
// 设置纹理大小
- (void)setImageSize:(CGSize)newImageSize;
// 锁定、与解锁帧缓存
- (void)lockFramebufferForReading;
- (void)unlockFramebufferAfterReading;

方法实现如下：

// 获取特定位置的像素向量
- (GPUByteColorVector)colorAtLocation:(CGPoint)locationInImage;
{
    // 将数据转为GPUByteColorVector类型
    GPUByteColorVector *imageColorBytes = (GPUByteColorVector *)self.rawBytesForImage;
//    NSLog(@"Row start");
//    for (unsigned int currentXPosition = 0; currentXPosition < (imageSize.width * 2.0); currentXPosition++)
//    {
//        GPUByteColorVector byteAtPosition = imageColorBytes[currentXPosition];
//        NSLog(@"%d - %d, %d, %d", currentXPosition, byteAtPosition.red, byteAtPosition.green, byteAtPosition.blue);
//    }
//    NSLog(@"Row end");

//    GPUByteColorVector byteAtOne = imageColorBytes[1];
//    GPUByteColorVector byteAtWidth = imageColorBytes[(int)imageSize.width - 3];
//    GPUByteColorVector byteAtHeight = imageColorBytes[(int)(imageSize.height - 1) * (int)imageSize.width];
//    NSLog(@"Byte 1: %d, %d, %d, byte 2: %d, %d, %d, byte 3: %d, %d, %d", byteAtOne.red, byteAtOne.green, byteAtOne.blue, byteAtWidth.red, byteAtWidth.green, byteAtWidth.blue, byteAtHeight.red, byteAtHeight.green, byteAtHeight.blue);

    // 控制边界，0 < x < width, 0 < y < height,
    CGPoint locationToPickFrom = CGPointZero;
    locationToPickFrom.x = MIN(MAX(locationInImage.x, 0.0), (imageSize.width - 1.0));
    locationToPickFrom.y = MIN(MAX((imageSize.height - locationInImage.y), 0.0), (imageSize.height - 1.0));

    // 如果是BGRA输出，则把RGBA数据转为BGRA数据
    if (outputBGRA)    
    {
        GPUByteColorVector flippedColor = imageColorBytes[(int)(round((locationToPickFrom.y * imageSize.width) + locationToPickFrom.x))];
        GLubyte temporaryRed = flippedColor.red;

        flippedColor.red = flippedColor.blue;
        flippedColor.blue = temporaryRed;

        return flippedColor;
    }
    else
    {
        // 返回某个位置的像素向量
        return imageColorBytes[(int)(round((locationToPickFrom.y * imageSize.width) + locationToPickFrom.x))];
    }
}

// 每行数据大小
- (NSUInteger)bytesPerRowInOutput;
{
    return [retainedFramebuffer bytesPerRow];
}

// 设置输出纹理大小
- (void)setImageSize:(CGSize)newImageSize {
    imageSize = newImageSize;
    if (_rawBytesForImage != NULL && (![GPUImageContext supportsFastTextureUpload]))
    {
        free(_rawBytesForImage);
        _rawBytesForImage = NULL;
    }
}

// 锁定帧缓存
- (void)lockFramebufferForReading;
{
    lockNextFramebuffer = YES;
}

// 解锁帧缓存
- (void)unlockFramebufferAfterReading;
{
    [retainedFramebuffer unlockAfterReading];
    [retainedFramebuffer unlock];
    retainedFramebuffer = nil;
}

// 获取RGBA数据
- (GLubyte *)rawBytesForImage;
{
    if ( (_rawBytesForImage == NULL) && (![GPUImageContext supportsFastTextureUpload]) )
    {
        // 申请空间，储存读取的数据
        _rawBytesForImage = (GLubyte *) calloc(imageSize.width * imageSize.height * 4, sizeof(GLubyte));
        hasReadFromTheCurrentFrame = NO;
    }

    if (hasReadFromTheCurrentFrame)
    {
        return _rawBytesForImage;
    }
    else
    {
        runSynchronouslyOnVideoProcessingQueue(^{
            // Note: the fast texture caches speed up 640x480 frame reads from 9.6 ms to 3.1 ms on iPhone 4S
            // 设置GL下文对象
            [GPUImageContext useImageProcessingContext];
            // 渲染到帧缓存
            [self renderAtInternalSize];

            if ([GPUImageContext supportsFastTextureUpload])
            {
                // 等待绘制结束
                glFinish();
                _rawBytesForImage = [outputFramebuffer byteBuffer];
            }
            else
            {
                // 以RGBA的形式读取数据
                glReadPixels(0, 0, imageSize.width, imageSize.height, GL_RGBA, GL_UNSIGNED_BYTE, _rawBytesForImage);
                // GL_EXT_read_format_bgra
                //            glReadPixels(0, 0, imageSize.width, imageSize.height, GL_BGRA_EXT, GL_UNSIGNED_BYTE, _rawBytesForImage);
            }

            hasReadFromTheCurrentFrame = YES;

        });

        return _rawBytesForImage;
    }
}