C++ OpenGL TGA 加载失败

Question

我一直在学习有关加载 TGA 文件的基本 OpenGl 教程，以用作 3d 对象的纹理。我已经能够从 TGA header 加载数据，但是当我尝试加载实际图像数据时，它失败了。我不确定哪里出了问题。这是我的纹理加载类:

头文件:

    struct TGA_Header 
{
    GLbyte  ID_Length;
    GLbyte  ColorMapType;
    GLbyte  ImageType;
    // Color map specifications
    GLbyte firstEntryIndex[2];      
    GLbyte colorMapLength[2];
    GLbyte colorMapEntrySize;

    //image specification
    GLshort xOrigin;
    GLshort yOrigin;
    GLshort ImageWidth;
    GLshort ImageHeight;
    GLbyte  PixelDepth;
    GLbyte ImageDescriptor;
};

class Texture
{
public:
    Texture(string in_filename, string in_name = "");
    ~Texture();

public:
    unsigned short  width;
    unsigned short  height;
    unsigned int    length;
    unsigned char   type;   
    unsigned char   *imageData;
    unsigned int    bpp;
    unsigned int    texID;

    string          name;

    static vector<Texture *> textures;

private:
    bool loadTGA(string filename);
    bool createTexture(unsigned char *imageData, int width, int height, int type);

    void swap(unsigned char * ori, unsigned char * dest, GLint size);
    void flipImage(unsigned char * image, bool flipHorizontal, bool flipVertical, GLushort width, GLushort height, GLbyte bpp);
};

这是cpp中的加载TGA函数:

bool Texture::loadTGA(string filename)
{
    TGA_Header TGAheader;

    ifstream file( filename.data(), std::ios::in, std::ios::binary );

    //make sure the file was opened properly
    if (!file.is_open() )
        return false;

    if( !file.read( (char *)&TGAheader, sizeof(TGAheader) ) )
        return false;


    //make sure the image is of a type we can handle
    if( TGAheader.ImageType != 2 )
        return false;

    width = TGAheader.ImageWidth;
    height = TGAheader.ImageHeight;
    bpp = TGAheader.PixelDepth;

    if( width < 0   ||              // if the width or height is less than 0, than
        height <= 0 ||              // the image is corrupt
        (bpp != 24 && bpp != 32) )  // make sure we are of the correct bit depth
    {
        return false;
    }

    //check for an alpha channel
    GLuint type = GL_RGBA;
    if ( bpp == 24 )
        type = GL_RGB;

    GLuint bytesPerPixel = bpp / 8;

    //allocate memory for the TGA so we can read it
    GLuint imageSize = width * height * bytesPerPixel;
    imageData = new GLubyte[imageSize];

    if ( imageData == NULL )
        return false;

    //make sure we are in the correct position to load the image data
    file.seekg(-imageSize, std::ios::end);

    // if something when wrong, make sure we free up the memory
    //NOTE: It never gets past this point. The conditional always fails.
    if ( !file.read( (char *)imageData, imageSize ) )
    {
        delete imageData;

        return false;
    }

    //more code is down here, but it doesnt matter because it does not pass the above function
}

好像加载了一些数据，但是一直返回失败。任何关于为什么的帮助将不胜感激。抱歉，如果它变得有点罗嗦，但我不确定什么是重要的或不重要的。

更新:所以，我只是重写了函数。我使用的 ifsteam 似乎是问题的原因。具体来说，它会尝试加载比我输入的多得多的数据字节。我不知道行为的原因，但我在下面列出了我的功能代码。谢谢大家的帮助。

Answer 1

问题可能取决于不支持压缩 TGA 的 TGA 算法。

确保您没有压缩 TGA 并且 TGA 顺序(不太重要)位于左下原点。

我通常使用 GIMP，此时，取消选中 RLE 压缩并放置左下对齐。