unity 图片的三种缩放加载方式

	public enum ImageZoomType
    {
    
    
        None = 0,  //强制压缩
        Max = 1,  //按短边压缩
        Min = 2,  //按长边压缩
    }

    /// <summary>
    /// 载入图片
    /// </summary>
    /// <param name="targetImg"></param>
    /// <param name="curSprite"></param>
    /// <param name="zoomType"></param>
    private void UpdateSprite(Image targetImg, Sprite curSprite, ImageZoomType zoomType = 0)
    {
    
    
        if (zoomType == ImageZoomType.None)
        {
    
    
            targetImg.sprite = curSprite;
            return;
        }

        Vector2 imgSize = targetImg.GetComponent<RectTransform>().rect.size;

        targetImg.sprite = curSprite;

        targetImg.SetNativeSize();

        float xScale = imgSize.x / curSprite.rect.width;
        float yScale = imgSize.y / curSprite.rect.height;
        float setScale = 1;
        if (zoomType == ImageZoomType.Min)
        {
    
    
            setScale = Mathf.Min(xScale, yScale);
        }
        else if (zoomType == ImageZoomType.Max)
        {
    
    
            setScale = Mathf.Max(xScale, yScale);
        }

        targetImg.transform.localScale = Vector3.one * setScale;
    }