加载TGA文件并将其与OpenGL一起使用 [英] Loading a TGA File and Using it with OpenGL

问题描述

我目前正在尝试使用c ++加载标记文件并使用OpenGL进行渲染。目前颜色都是混合的（红色变为蓝色，绿色变为红色，蓝色变为绿色）。我目前将其放入视频内存的代码是。

I currently am trying to load a tag file with c++ and rendering it with OpenGL. Currently the colors are all mixed up (red becomes blue, green becomes red, and blue becomes green). My current code for putting it into the video memory is.

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

数据是像素数据，其余部分是自解释的。从photoshop保存的24位保存文件没有压缩。

Where the data is the pixel data and the rest is self explanatory. The files are saved with no compression are in 24 bits saved from photoshop.

推荐答案

你的 glTexImage2D 是正确的，所以这不是问题。

Your glTexImage2D is correct, so that's not the problem.

我需要（在加载TGA文件时）交换颜色组件。试试这个：

I do need (when loading TGA files) to swap the color components. Try this:

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;
}

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