今天有人问cocos2dx的纹理格式有哪些，懵了，啥是“纹理格式”？
其实就是PixelFormat-像素格式，在CCtexture2d.h中有列出
enum class PixelFormat
{
//! auto detect the type
AUTO,
//! 32-bit texture: BGRA8888
BGRA8888,
//! 32-bit texture: RGBA8888
RGBA8888,
//! 24-bit texture: RGBA888
RGB888,
//! 16-bit texture without Alpha channel
RGB565,
//! 8-bit textures used as masks
A8,
//! 8-bit intensity texture
I8,
//! 16-bit textures used as masks
AI88,
//! 16-bit textures: RGBA4444
RGBA4444,
//! 16-bit textures: RGB5A1
RGB5A1,
//! 4-bit PVRTC-compressed texture: PVRTC4
PVRTC4,
//! 4-bit PVRTC-compressed texture: PVRTC4 (has alpha channel)
PVRTC4A,
//! 2-bit PVRTC-compressed texture: PVRTC2
PVRTC2,
//! 2-bit PVRTC-compressed texture: PVRTC2 (has alpha channel)
PVRTC2A,
//! ETC-compressed texture: ETC
ETC,
//! S3TC-compressed texture: S3TC_Dxt1
S3TC_DXT1,
//! S3TC-compressed texture: S3TC_Dxt3
S3TC_DXT3,
//! S3TC-compressed texture: S3TC_Dxt5
S3TC_DXT5,
//! ATITC-compressed texture: ATC_RGB
ATC_RGB,
//! ATITC-compressed texture: ATC_EXPLICIT_ALPHA
ATC_EXPLICIT_ALPHA,
//! ATITC-compresed texture: ATC_INTERPOLATED_ALPHA
ATC_INTERPOLATED_ALPHA,
//! Default texture format: AUTO
DEFAULT = AUTO,
NONE = -1
};