Let's continue our previous method which is GraphicsManager::loadTexture().

Generate a new texture identifier with glGenTextures().

Indicate that we are working on a texture with glBindTexture().

Configure texture parameters with glTexParameteri() to specify the way a texture is filtered and wrapped. Use GL_NEAREST, as smoothing is not essential for a 2D game without zoom effects. Texture repetition is also not necessary and can be prevented with GL_CLAMP_TO_EDGE:

...
    png_destroy_read_struct(&pngPtr, &infoPtr, NULL);
    delete[] rowPtrs;

    GLenum errorResult;
    glGenTextures(1, &texture);
    glBindTexture(GL_TEXTURE_2D, texture);
    // Set-up texture properties.
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
        GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
        GL_NEAREST...