AndEngine中TextureOptions的區別

在學習AndEngine中的貼圖，發現TextureOptions有多種選項在源碼中如下：

public static final TextureOptions NEAREST = new TextureOptions(GLES20.GL_NEAREST, GLES20.GL_NEAREST, GLES20.GL_CLAMP_TO_EDGE, GLES20.GL_CLAMP_TO_EDGE, false);public static final TextureOptions BILINEAR = new TextureOptions(GLES20.GL_LINEAR, GLES20.GL_LINEAR, GLES20.GL_CLAMP_TO_EDGE, GLES20.GL_CLAMP_TO_EDGE, false);public static final TextureOptions REPEATING_NEAREST = new TextureOptions(GLES20.GL_NEAREST, GLES20.GL_NEAREST, GLES20.GL_REPEAT, GLES20.GL_REPEAT, false);public static final TextureOptions REPEATING_BILINEAR = new TextureOptions(GLES20.GL_LINEAR, GLES20.GL_LINEAR, GLES20.GL_REPEAT, GLES20.GL_REPEAT, false);public static final TextureOptions NEAREST_PREMULTIPLYALPHA = new TextureOptions(GLES20.GL_NEAREST, GLES20.GL_NEAREST, GLES20.GL_CLAMP_TO_EDGE, GLES20.GL_CLAMP_TO_EDGE, true);public static final TextureOptions BILINEAR_PREMULTIPLYALPHA = new TextureOptions(GLES20.GL_LINEAR, GLES20.GL_LINEAR, GLES20.GL_CLAMP_TO_EDGE, GLES20.GL_CLAMP_TO_EDGE, true);public static final TextureOptions REPEATING_NEAREST_PREMULTIPLYALPHA = new TextureOptions(GLES20.GL_NEAREST, GLES20.GL_NEAREST, GLES20.GL_REPEAT, GLES20.GL_REPEAT, true);public static final TextureOptions REPEATING_BILINEAR_PREMULTIPLYALPHA = new TextureOptions(GLES20.GL_LINEAR, GLES20.GL_LINEAR, GLES20.GL_REPEAT, GLES20.GL_REPEAT, true);public static final TextureOptions DEFAULT = NEAREST;

在其論壇中有網友給出了如下說明：

- NEAREST: Faster then BILINEAR as only the nearest pixel on the
Texture is used (Sprites tend to look pixelated when, physical resolution is higher or lower than texture resolution. Up/Down-scaling)
- BILINEAR: Slower than NEAREST, but looks better, as not only one pixel from the texture is fetched but the 4 nearest.

The difference between those and the REPEATING TextureOptions is the way OpenGL treats TextureCoordinates that are out of the physical bounds of the Texture (usually ranging from 0.0 to 1.0).
Where REPEATING paints the Texture twice when the coordinates go from 0.0 to 2.0, NON-REPEATING will stretch the outermost pixel of the Texture what looks pretty ugly.

So the REPEATING TextureOptions are used only in very special cases.

For a description what the PREMULTIPLYALPHA-thing is, have a look here:
點擊開啟連結

大致就是說NEAREST要比BILINEAR快，因為NEAREST在縮放時使用距離縮放位置最近的一個像素而BILINEAR要使用最近的4個像素來確定縮放位置的最終顯示效果。但是BILINEAR所得到的效果要比EAREST好。

帶REPEATING的只在特殊情況下使用。