Alpha分离

2016-10-31

1. 为什么要进行Alpha分离？

使得图集可以压缩，减小包量。

2. Alpha分离要点

1. 分离

收集图集

List<Texture2D> m_AtlasList = new List<Texture2D>();
private void CollectAtlasSprite()
{
    //Travel all AtlasSprite
    m_AtlasList.Add(obj as Texture2D);
}

分离单张图集的Alpha

public static void separateOneTexture(Texture2D sourceTex)
{
    string sourceTexPath= AssetDatabase.GetAssetPath(sourceTex);  
    //创建2张RGB格式的纹理，最后保存的时候会把rgba的alpha丢弃掉。
    Texture2D texRGB = new Texture2D(sourceTex.width, sourceTex.height, TextureFormat.RGB24, false);
    Texture2D texAlpha = new Texture2D(sourceTex.width, sourceTex.height, TextureFormat.RGB24, false);
    //取得原始像素数据
    Color[] srcColors = sourceTex.GetPixels();
    texRGB.SetPixels(srcColors);
    //生成 rgba = (a, a, a, a) 的图片
    Color[] alphaColors = new Color[srcColors.Length];
    for(int i=0;i<srcColors.Length;i++)
    {
        alphaColors[i].r = srcColors[i].a;
        alphaColors[i].g = srcColors[i].a;
        alphaColors[i].b = srcColors[i].a;
    }
    texAlpha.SetPixels(alphaColors);
    texRGB.Apply();
    texAlpha.Apply();
    byte[] rgbBytes = texRGB.EncodeToPNG();
    File.WriteAllBytes(sourceTexPath, rgbBytes);
    byte[] alphaBytes = texAlpha.EncodeToPNG();
    File.WriteAllBytes(alphaTexPath, alphaBytes);
}

记得检查图片的AssetImporter.GetAtPath(sourceTexFullPath).isReadable == true，否则不能进行SetPixels和GetPixels操作

2. 合并

合并Alpha图片和RGB图片


public static void mergeTwoTexture(Texture2D t2dRGB,Texture2D t2dAlpha)
{
    string strRGBPath = AssetDatabase.GetAssetPath(t2dRGB);
    string strAlphaPath = AssetDatabase.GetAssetPath(t2dAlpha);
    TextureImporter importerRGBTex = AssetImporter.GetAtPath(strRGBPath) as TextureImporter;
    if (!importerRGBTex.isReadable)
    {
        //检查isReadable属性
        importerRGBTex.isReadable = true;
        AssetDatabase.ImportAsset(strRGBPath);
    }
    TextureImporter importerAlphaTex = AssetImporter.GetAtPath(strAlphaPath) as TextureImporter;
    if(!importerAlphaTex.isReadable)
    {
        //检查isReadable属性
        importerAlphaTex.isReadable = true;
        AssetDatabase.ImportAsset(strAlphaPath);
    }
    Color[] rgbDatas = t2dRGB.GetPixels();
    Color[] alphaDatas = t2dAlpha.GetPixels();
    Color[] rgbaDatas = new Color[rgbDatas.Length];            
    Texture2D texRGBA = new Texture2D(t2dRGB.width, t2dRGB.height, TextureFormat.RGBA32,false);
    for(int nI=0;nI<rgbaDatas.Length;nI++)
    {
        rgbaDatas[nI].r = rgbDatas[nI].r;
        rgbaDatas[nI].g = rgbDatas[nI].g;
        rgbaDatas[nI].b = rgbDatas[nI].b;
        rgbaDatas[nI].a = alphaDatas[nI].r;
    }
    texRGBA.SetPixels(rgbaDatas);
    texRGBA.Apply();
    byte[] rgbaBytes = texRGBA.EncodeToPNG();
    File.WriteAllBytes(strRGBPath, rgbaBytes);
    AssetDatabase.DeleteAsset(strAlphaPath);
    AssetDatabase.Refresh();
    ReImportAsset(strRGBPath);         
}