原因

想要在編輯器擴展也能訪問FairyGUI圖集里面的小圖，隨便找了一下沒有找到接口自己做一個

方法

使用UIPackage.GetItemByURL獲得小圖信息。從圖集中復(fù)制出小圖，如果有旋轉(zhuǎn)就逆旋轉(zhuǎn)90度即可
圖集里面的小圖是有可能旋轉(zhuǎn)的，可以通過訪問 NTexture.rotated 判斷在圖集中是否旋轉(zhuǎn)

獲取小圖在圖集中的起始位置

X偏移坐標可以直接 uvRect.min.x * nativeTexture.width 得到真實的X偏移
Y坐標可以根據(jù)uvRect賦值反過來獲得，原有公式是

uvRect.min.y = 1 - region.yMax / _nativeTexture.height

那么真實的公式就是

y = (1 - startOffset.y) * nativeTexture.height - textureSize.y

無非就是交互律。還原public NTexture(Texture texture, Rect region) 構(gòu)造傳入來的region參數(shù)

獲得偏移和大小后只需要使用RenderTexture把小圖讀出來就好

        RenderTexture renderTex = RenderTexture.GetTemporary(nativeTexture.width, nativeTexture.height, 24, RenderTextureFormat.Default, RenderTextureReadWrite.Linear);
        Graphics.Blit(nativeTexture, renderTex);
        RenderTexture previous = RenderTexture.active;
        RenderTexture.active = renderTex;

        Texture2D resultTexture = new Texture2D(textureSize.x, textureSize.y, nativeTexture.format, false);
        resultTexture.ReadPixels(new Rect((int)startOffset.x, (int)startOffset.y, textureSize.x, textureSize.y), 0, 0);
        resultTexture.Apply();

        RenderTexture.active = previous;
        RenderTexture.ReleaseTemporary(renderTex);

圖集中的小圖是會旋轉(zhuǎn)的應(yīng)該如何還原

Texture2D.GetPixel 和 Texture2D.SetPixel 接口讀寫非常慢
可以直接使用GetPixelData或者GetPixels導(dǎo)出圖像數(shù)據(jù)數(shù)組，操作完成后刷新圖像數(shù)據(jù)
根據(jù) nativeTexture.format 類型使用Color或者Color32格式讀取

var colorArray = resultTexture.GetPixelData<Color32>(0)

有數(shù)組后簡單逆旋轉(zhuǎn)90數(shù)組數(shù)據(jù)，就可以得到原來的小圖文章來源地址http://www.zghlxwxcb.cn/news/detail-709356.html

for (int i = 0; i < textureSize.x; i++)
{
    for (int j = 0; j < textureSize.y; j++)
    {
        colors[i * textureSize.y + j] = colorArray[textureSize.x - 1 - i + j * textureSize.x];
    }
}

完整代碼

    public Texture GetTexture(string url)
    {
        PackageItem packageItem = UIPackage.GetItemByURL(url);
        if (packageItem == null)
            return null;

        NTexture nTexture = packageItem.texture;
        Texture2D nativeTexture = nTexture.nativeTexture as Texture2D;

        var startOffset = nTexture.uvRect.min;
        var textureSize = new Vector2Int(nTexture.width, nTexture.height);
        if (nTexture.rotated)
            textureSize = new Vector2Int(nTexture.height, nTexture.width);
        startOffset.x *= nativeTexture.width;
        startOffset.y = (1 - startOffset.y) * nativeTexture.height - textureSize.y;


        RenderTexture renderTex = RenderTexture.GetTemporary(nativeTexture.width, nativeTexture.height, 24, RenderTextureFormat.Default, RenderTextureReadWrite.Linear);
        Graphics.Blit(nativeTexture, renderTex);
        RenderTexture previous = RenderTexture.active;
        RenderTexture.active = renderTex;

        Texture2D resultTexture = new Texture2D(textureSize.x, textureSize.y, nativeTexture.format, false);
        resultTexture.ReadPixels(new Rect((int)startOffset.x, (int)startOffset.y, textureSize.x, textureSize.y), 0, 0);
        resultTexture.Apply();

        RenderTexture.active = previous;
        RenderTexture.ReleaseTemporary(renderTex);

        if (nTexture.rotated)
        {
            var colorArray = resultTexture.GetPixelData<Color32>(0);
            Texture2D rotationTexture = new Texture2D(textureSize.y, textureSize.x, nativeTexture.format, false);
            var colors = rotationTexture.GetPixelData<Color32>(0);

            for (int i = 0; i < textureSize.x; i++)
            {
                for (int j = 0; j < textureSize.y; j++)
                {
                    colors[i * textureSize.y + j] = colorArray[textureSize.x - 1 - i + j * textureSize.x];
                }
            }

            rotationTexture.SetPixelData(colors, 0);
            rotationTexture.Apply();
            Object.Destroy(resultTexture);
            resultTexture = rotationTexture;
        }

        return resultTexture;
    }

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