openGL之API学习（二一零）纹理要素设置过程

Posted 2022-02-24 hankern

包括纹理尺寸、格式、类型、边框

边框在构造是置为0，后期不再修改

1、在读取图片时确定

内部格式和像素格式是一样的

osgPlugins/rgb/ReaderWriterRGB.cpp
ReadResult readRGBStream(std::istream& fin) const

    osg::ref_ptr<refImageRec> raw;

    if( (raw = RawImageOpen(fin)) == NULL )
    
        return ReadResult::ERROR_IN_READING_FILE;
    

    int s = raw->sizeX;
    int t = raw->sizeY;
    int r = 1;

    unsigned int pixelFormat =
        raw->sizeZ == 1 ? GL_LUMINANCE :
        raw->sizeZ == 2 ? GL_LUMINANCE_ALPHA :
        raw->sizeZ == 3 ? GL_RGB :
        raw->sizeZ == 4 ? GL_RGBA : (GLenum)-1;

    int internalFormat = pixelFormat;

    unsigned int dataType = raw->bpc == 1 ? GL_UNSIGNED_BYTE :
      GL_UNSIGNED_SHORT;

    unsigned char *data;
    RawImageGetData(*raw, &data);

    Image* image = new Image();
    image->setImage(s,t,r,
        internalFormat,
        pixelFormat,
        dataType,
        data,
        osg::Image::USE_NEW_DELETE);

    OSG_INFO << "image read ok "<<s<<"  "<<t<< std::endl;
    return image;

osg/Image.cpp
void Image::setImage(int s,int t,int r,
                     GLint internalTextureFormat,
                     GLenum format,GLenum type,
                     unsigned char *data,
                     AllocationMode mode,
                     int packing,
                     int rowLength)

    _mipmapData.clear();

    bool callback_needed = (_s != s) || (_t != t) || (_r != r);

    _s = s;
    _t = t;
    _r = r;

    _internalTextureFormat = internalTextureFormat;
    _pixelFormat    = format;
    _dataType       = type;

    setData(data,mode);

    _packing = packing;
    _rowLength = rowLength;

    dirty();

    if (callback_needed)
        handleDimensionsChangedCallbacks();

 

在apply时设置内部格式

 

osg/Texture.cpp
void Texture::computeInternalFormatWithImage(const osg::Image& image) const

    internalFormat = image.getInternalTextureFormat();

在apply时设置纹理尺寸

 

osg/Texture.cpp
void Texture::computeRequiredTextureDimensions(State& state, const osg::Image& image,GLsizei& inwidth, GLsizei& inheight,GLsizei& numMipmapLevels) const

    width = Image::computeNearestPowerOfTwo(image.s()-2*_borderWidth)+2*_borderWidth;
    height = Image::computeNearestPowerOfTwo(image.t()-2*_borderWidth)+2*_borderWidth;
    inwidth = width;
    inheight = height;
    if( _min_filter == LINEAR || _min_filter == NEAREST)
    
        numMipmapLevels = 1;
    
    else if( image.isMipmap() )
    
        numMipmapLevels = image.getNumMipmapLevels();
    
    else
    
        numMipmapLevels = 1;
        for(int s=1; s<width || s<height; s <<= 1, ++numMipmapLevels)