openGL——图片通道数量

// note that the awesomeface.png has transparency and thus an alpha channel, so make sure to tell OpenGL the data type is of GL_RGBA

请注意，Awesomeface.png具有透明度，因此具有alpha通道，因此请确保告诉OpenGL数据类型为GL_RGBA

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 png格式比jpg格式通道数量多，openGL中参数不同

int width, height, nrChannels;
unsigned char *data = stbi_load("../include/pic/awesomeface.png", &width, &height, &nrChannels, 0);
//unsigned char *data = stbi_load("../include/pic/awesomefaceJpg.jpg", &width, &height, &nrChannels, 0);
if (data)
{
    // note that the awesomeface.png has transparency and thus an alpha channel, so make sure to tell OpenGL the data type is of GL_RGBA
    GLenum format;
    if (nrChannels == 1)
        format = GL_RED;
    else if (nrChannels == 3)
        format = GL_RGB;
    else if (nrChannels == 4)
        format = GL_RGBA;
    //glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
    glTexImage2D(GL_TEXTURE_2D, 0, format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
    glGenerateMipmap(GL_TEXTURE_2D);
}