加载 TGA 文件并将其与 OpenGL 一起使用

Question

我目前正在尝试使用 C++ 加载标签文件并使用 OpenGL 渲染它。目前颜色都是混合的（红色变成蓝色，绿色变成红色，蓝色变成绿色）。我当前将其放入视频内存的代码是。

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);

其中数据是像素数据，其余的都是不言自明的。文件以 24 位格式从 Photoshop 中保存，未压缩保存。

Answer 1

您的 glTexImage2D 是正确的，所以这不是问题。

我确实需要（加载 TGA 文件时）交换颜色分量。试试这个：

typedef struct
{
    unsigned char imageTypeCode;
    short int imageWidth;
    short int imageHeight;
    unsigned char bitCount;
    unsigned char *imageData;
} TGAFILE;

bool LoadTGAFile(char *filename, TGAFILE *tgaFile)
{
    FILE *filePtr;
    unsigned char ucharBad;
    short int sintBad;
    long imageSize;
    int colorMode;
    unsigned char colorSwap;

    // Open the TGA file.
    filePtr = fopen(filename, "rb");
    if (filePtr == NULL)
    {
        return false;
    }

    // Read the two first bytes we don't need.
    fread(&ucharBad, sizeof(unsigned char), 1, filePtr);
    fread(&ucharBad, sizeof(unsigned char), 1, filePtr);

    // Which type of image gets stored in imageTypeCode.
    fread(&tgaFile->imageTypeCode, sizeof(unsigned char), 1, filePtr);

    // For our purposes, the type code should be 2 (uncompressed RGB image)
    // or 3 (uncompressed black-and-white images).
    if (tgaFile->imageTypeCode != 2 && tgaFile->imageTypeCode != 3)
    {
        fclose(filePtr);
        return false;
    }

    // Read 13 bytes of data we don't need.
    fread(&sintBad, sizeof(short int), 1, filePtr);
    fread(&sintBad, sizeof(short int), 1, filePtr);
    fread(&ucharBad, sizeof(unsigned char), 1, filePtr);
    fread(&sintBad, sizeof(short int), 1, filePtr);
    fread(&sintBad, sizeof(short int), 1, filePtr);

    // Read the image's width and height.
    fread(&tgaFile->imageWidth, sizeof(short int), 1, filePtr);
    fread(&tgaFile->imageHeight, sizeof(short int), 1, filePtr);

    // Read the bit depth.
    fread(&tgaFile->bitCount, sizeof(unsigned char), 1, filePtr);

    // Read one byte of data we don't need.
    fread(&ucharBad, sizeof(unsigned char), 1, filePtr);

    // Color mode -> 3 = BGR, 4 = BGRA.
    colorMode = tgaFile->bitCount / 8;
    imageSize = tgaFile->imageWidth * tgaFile->imageHeight * colorMode;

    // Allocate memory for the image data.
    tgaFile->imageData = (unsigned char*)malloc(sizeof(unsigned char)*imageSize);

    // Read the image data.
    fread(tgaFile->imageData, sizeof(unsigned char), imageSize, filePtr);

    // Change from BGR to RGB so OpenGL can read the image data.
    for (int imageIdx = 0; imageIdx < imageSize; imageIdx += colorMode)
    {
        colorSwap = tgaFile->imageData[imageIdx];
        tgaFile->imageData[imageIdx] = tgaFile->imageData[imageIdx + 2];
        tgaFile->imageData[imageIdx + 2] = colorSwap;
    }

    fclose(filePtr);
    return true;
}

Answer 2

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, Width,Height, 0,
         GL_BGRA_EXT, GL_UNSIGNED_BYTE, Pixels);

尝试一下，我遇到了同样的问题，每样东西都是蓝色的，它有纹理图案，只是不是
颜色