Unity批量压缩图片的功能实现_unity 批量压缩图片

在不同平台下开发时，可能会遇到改变图片压缩格式的需求。这里把我之前实现的功能分享给各位。
可以学到的知识点如下：

• 拿到原始图片的大小
• 判断一个数是不是2的次幂
• 编辑器扩展之增加菜单按钮、显示对话框、显示进度条
• 安卓和IOS平台的图片压缩格式

public class TextureCompressOnPhone
{
    private const string AndroidPlatformName = "Android";

    private const string IOSPlatformName = "iPhone";
    
	[MenuItem( "Tools/Android/CompressTexture" )]
	private static void CompressTextureOnAndroid()
    {
        CompressInPlotform(AndroidPlatformName);
    }

    [MenuItem( "Tools/IOS/CompressTexture" )]
    private static void CompressTextureOnIOS()
    {
        CompressInPlotform(IOSPlatformName);
    }

    private static void CompressInPlotform( string platform )
    {
        var message = "You are going to perform the following operation to ALL Texture2D! Continue?\n";

        //弹出对话框进行二次确认
        if (EditorUtility.DisplayDialog("Change Max Size", message, "OK", "Cancel") == false)
        {
            return;
        }
        
        // 显示进度条
        EditorUtility.DisplayProgressBar("Change Max Size", "", 0.0f);
        
        // 找到所有纹理
        var guids = AssetDatabase.FindAssets("t:Texture2D");
        for (int i = 0; i < guids.Length; i++)
        {
            var dialogTitle = "Change Max Size" + " (" + i + "/" + guids.Length + ")";
            var progress = (float)i / guids.Length;
            var guid = guids[i];
            var path = AssetDatabase.GUIDToAssetPath(guid);
            var go = AssetDatabase.LoadAssetAtPath<Texture2D>(path);
            if (go == null)
            {
                continue;
            }

            EditorUtility.DisplayProgressBar(dialogTitle, go.name, progress);

            //拿到TextureImporter才能对图片进行压缩
            var assetImporter = AssetImporter.GetAtPath(path);
            if (assetImporter != null)
            {
                var textureImporter = assetImporter as TextureImporter;
                if (textureImporter == null)
                {
                    Debug.LogWarningFormat(go, "MissingImporter Texture2D: '{0}'", go.name);
                    continue;
                }
                //拿到不压缩前的size
                var defaultMaxSize = textureImporter.maxTextureSize;
                TextureImporterPlatformSettings platformImporter = textureImporter.GetPlatformTextureSettings(platform);
                platformImporter.overridden = true;
                platformImporter.maxTextureSize = defaultMaxSize / 4;
                var width = 0;
                var height = 0;
                //拿到宽高
                GetTextureRealWidthAndHeight(textureImporter, ref width, ref height);

                //判断有无alpha
                var haveAlpha = textureImporter.DoesSourceTextureHaveAlpha();
                platformImporter.format = GetCompressFormat(platform, width, height, haveAlpha);

                textureImporter.SetPlatformTextureSettings(platformImporter);

                EditorUtility.SetDirty(go);
                Debug.LogFormat(go, "Processed Texture2D: '{0}'", go.name);
                textureImporter.SaveAndReimport();
            }
        }

        AssetDatabase.SaveAssets();
        EditorUtility.ClearProgressBar();
    }

    // 得到目标压缩格式
    private static TextureImporterFormat GetCompressFormat( string platform , int width, int height ,bool haveAlpha )
    {
    
        //分几种情况讨论，是不是2的次幂以及是不是有alpha通道
        var isPowerOfTwo = WidthAndHeightIsPowerOfTwo(width, height);
        if ( isPowerOfTwo == false )
        {
            if ( haveAlpha )
            {
                return TextureImporterFormat.RGBA16;
            }
            else
            {
                return TextureImporterFormat.RGB16;
            }
        }
        else
        {
            if ( platform == AndroidPlatformName )
            {
                if( haveAlpha )
                {
                    return TextureImporterFormat.ETC2_RGBA8Crunched;
                }
                else
                {
                    return TextureImporterFormat.ETC_RGB4Crunched;
                }
            }
            else if( platform == IOSPlatformName)
            {
                if( haveAlpha )
                {
                    return TextureImporterFormat.PVRTC_RGBA4;
                }
                else
                {
                    return TextureImporterFormat.PVRTC_RGB4;
                }
            }
        }
        return TextureImporterFormat.RGBA16;
    }
    
    // 判断宽和高是否是2的次幂
    private static bool WidthAndHeightIsPowerOfTwo( int width, int height )
    {
        if ( IsPowerOfTwo(width) && IsPowerOfTwo(height) )
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    //用二进制与运算，如果一个数是2的次幂，n&(n-1) = 0
    private static bool IsPowerOfTwo( int number )
    {
        if ( number <= 0 )
        {
            return false;
        }

        return ( number & ( number - 1 ) ) == 0;
    }

    //得到要压缩成几分之一，这里是二分之一
    private static int GetCompressedMaxSize( int sourceMaxSize )
	{
		return sourceMaxSize / 2;
	}
	
    //用反射得到纹理宽高
	public static void GetTextureRealWidthAndHeight( TextureImporter texImpoter, ref int width, ref int height )
	{
		System.Type type = typeof( TextureImporter );
		System.Reflection.MethodInfo method = type.GetMethod( "GetWidthAndHeight", BindingFlags.Instance | BindingFlags.NonPublic );
		var args = new object[] { width, height };
		method.Invoke( texImpoter, args );
		width = (int)args[0];
		height = (int)args[1];
	}
}
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