当我们往服务器保存图片时

并不会仅仅保留原图

一般会另外保存一张缩略图

当加载文件夹时只加载缩略图

当在点击缩略图打开图片时

再加载原缩略图

以节省时间和内存

下面以将屏幕截图保存到服务器为例

将屏幕截图和截图缩略图保存到服务器

    private IEnumerator UploadPNG(string id)
    {
        yield return new WaitForEndOfFrame();

        int width = Screen.width;
        int height = Screen.height;

        //屏幕截图
        Texture2D tex = new Texture2D(width, height, TextureFormat.ARGB32, false);
        tex.ReadPixels(new Rect(0, 0, width, height), 0, 0);
        tex.Apply();
        byte[] bytes = tex.EncodeToPNG();

        //缩略图(256*256)
        Texture2D texThumb = new Texture2D(256, 256);
        
        //压缩图片
        Color[] destPix = new Color[texThumb.width * texThumb.height];
        float warpFactor = 1.0f;
        int y = 0;
        while (y < texThumb.height)
        {
            int x = 0;
            while (x < texThumb.width)
            {
                float xFrac = x * 1.0F / (texThumb.width - 1);
                float yFrac = y * 1.0F / (texThumb.height - 1);
                float warpXFrac = Mathf.Pow(xFrac, warpFactor);
                float warpYFrac = Mathf.Pow(yFrac, warpFactor);
                Color c0 = tex.GetPixelBilinear(warpXFrac, warpYFrac);

                xFrac = (x - 1) * 1.0F / (texThumb.width - 1);
                yFrac = y * 1.0F / (texThumb.height - 1);
                warpXFrac = Mathf.Pow(xFrac, warpFactor);
                warpYFrac = Mathf.Pow(yFrac, warpFactor);
                Color c1 = tex.GetPixelBilinear(warpXFrac, warpYFrac);

                xFrac = (x + 1) * 1.0F / (texThumb.width - 1);
                yFrac = y * 1.0F / (texThumb.height - 1);
                warpXFrac = Mathf.Pow(xFrac, warpFactor);
                warpYFrac = Mathf.Pow(yFrac, warpFactor);
                Color c2 = tex.GetPixelBilinear(warpXFrac, warpYFrac);

                xFrac = (x + 1) * 1.0F / (texThumb.width - 1);
                yFrac = (y - 1) * 1.0F / (texThumb.height - 1);
                warpXFrac = Mathf.Pow(xFrac, warpFactor);
                warpYFrac = Mathf.Pow(yFrac, warpFactor);
                Color c3 = tex.GetPixelBilinear(warpXFrac, warpYFrac);

                xFrac = (x - 0) * 1.0F / (texThumb.width - 1);
                yFrac = (y - 1) * 1.0F / (texThumb.height - 1);
                warpXFrac = Mathf.Pow(xFrac, warpFactor);
                warpYFrac = Mathf.Pow(yFrac, warpFactor);
                Color c4 = tex.GetPixelBilinear(warpXFrac, warpYFrac);

                xFrac = (x - 1) * 1.0F / (texThumb.width - 1);
                yFrac = (y - 1) * 1.0F / (texThumb.height - 1);
                warpXFrac = Mathf.Pow(xFrac, warpFactor);
                warpYFrac = Mathf.Pow(yFrac, warpFactor);
                Color c5 = tex.GetPixelBilinear(warpXFrac, warpYFrac);

                xFrac = (x + 1) * 1.0F / (texThumb.width - 1);
                yFrac = (y + 1) * 1.0F / (texThumb.height - 1);
                warpXFrac = Mathf.Pow(xFrac, warpFactor);
                warpYFrac = Mathf.Pow(yFrac, warpFactor);
                Color c6 = tex.GetPixelBilinear(warpXFrac, warpYFrac);

                xFrac = (x - 0) * 1.0F / (texThumb.width - 1);
                yFrac = (y + 1) * 1.0F / (texThumb.height - 1);
                warpXFrac = Mathf.Pow(xFrac, warpFactor);
                warpYFrac = Mathf.Pow(yFrac, warpFactor);
                Color c7 = tex.GetPixelBilinear(warpXFrac, warpYFrac);

                xFrac = (x - 1) * 1.0F / (texThumb.width - 1);
                yFrac = (y + 1) * 1.0F / (texThumb.height - 1);
                warpXFrac = Mathf.Pow(xFrac, warpFactor);
                warpYFrac = Mathf.Pow(yFrac, warpFactor);
                Color c8 = tex.GetPixelBilinear(warpXFrac, warpYFrac);

                Color cr = c0 * 0.25f + c1 * 0.125f + c2 * 0.125f + c3 * 0.0625f + c4 * 0.125f + c5 * 0.0625f + c6 * 0.0625f + c7 * 0.125f + c8 * 0.0625f;

                destPix[y * texThumb.width + x] = cr;

                x++;
            }
            y++;
        }
        texThumb.SetPixels(destPix);
        texThumb.Apply();
        byte[] bytesThumb = texThumb.EncodeToPNG();

        Destroy(tex);
        Destroy(texThumb);

        //WWWForm上传到服务器
        WWWForm form = new WWWForm();
        form.AddField("cmd", "savedraw");
        form.AddBinaryData("screenshot", bytesThumb);
        form.AddBinaryData("draw", bytes);

        WWW w = new WWW(url, form);
        yield return w;

        if (w.error != null)
        {
            Debug.Log("Error:" + w.error);
        }
        else
            Debug.Log("OK");
    }

Unity 压缩texture