背景:  .net core 中預設已經取消可以直接訪問圖片,因為這樣不安全. 導致我們上傳的圖片無法直接通過url訪問.

解決方案: 

一: 通過修改專案配置,使可以直接通過url訪問.(方法略,可以百度);

二: 圖片都通過介面返回,接口裡面讀取專案的圖片,然後返回流;

步驟:

1. 新建.net core 2.0 專案(過程略)

2. 通過nuget新增引用 System.Drawing.Common; .net core 開始的時候並沒有System.Drawing,在2.0之後新增了 System.Drawing.Common,用於替代原來的System.Drawing.用法基本一致

3. 寫介面了

a. 使用特性路由傳入想要的尺寸和檔名,這樣可以更好的用於前端展示,

b. 沒有找到圖片或者錯誤時返回預設的一張圖片

c. 需要注意引用 using System.IO;using System.Drawing;

d. .net core 中返回圖片不用 HttpResponseMessage 型別,而是直接採用 IActionResult. 而且封裝了FileContentResult類,可以直接返回.

e. .net core 中獲取當前專案的實體地址可以通過 AppContext.BaseDirectory 和.net 有區別

        /// <summary>
        /// 訪問圖片
        /// </summary>
        /// <param name="width">所訪問圖片的寬度,高度自動縮放,大於原圖尺寸或者小於等於0返回原圖</param>
        /// <param name="name">所要訪問圖片的名稱或者相對地址</param>
        /// <returns>圖片</returns>
        [HttpGet]
        [Route("file/image/{width}/{name}
 
")]
        public IActionResult GetImage(int width, string name)
        {
            var appPath = AppContext.BaseDirectory.Split("\\bin\\")[0] + "/image/";
            var errorImage = appPath + "404.png";//沒有找到圖片
            var imgPath = string.IsNullOrEmpty(name) ? errorImage : appPath + name;
            //獲取圖片的返回型別
            var contentTypDict = new Dictionary<string, string> {
                {"jpg","image/jpeg"},
                {"jpeg","image/jpeg"},
                {"jpe","image/jpeg"},
                {"png","image/png"},
                {"gif","image/gif"},
                {"ico","image/x-ico"},
                {"tif","image/tiff"},
                {"tiff","image/tiff"},
                {"fax","image/fax"},
                {"wbmp","image//vnd.wap.wbmp"},
                {"rp","image/vnd.rn-realpix"}
            };
            var contentTypeStr = "image/jpeg";
            var imgTypeSplit = name.Split('.');
            var imgType = imgTypeSplit[imgTypeSplit.Length - 1].ToLower();
            //未知的圖片型別
            if (!contentTypDict.ContainsKey(imgType))
            {
                imgPath = errorImage;
            }
            else
            {
                contentTypeStr = contentTypDict[imgType];
            }
            //圖片不存在
            if (!new FileInfo(imgPath).Exists)
            {
                imgPath = errorImage;
            }
            //原圖
            if (width <= 0)
            {
                using (var sw = new FileStream(imgPath, FileMode.Open))
                { 
                    var bytes = new byte[sw.Length];
                    sw.Read(bytes, 0, bytes.Length);
                    sw.Close();
                    return new FileContentResult(bytes, contentTypeStr);
                }
            }
            //縮小圖片
            using (var imgBmp = new Bitmap(imgPath))
            {
                //找到新尺寸
                var oWidth = imgBmp.Width;
                var oHeight = imgBmp.Height;
                var height = oHeight;
                if (width > oWidth)
                {
                    width = oWidth;
                }
                else
                {
                    height = width * oHeight / oWidth;
                }
                var newImg = new Bitmap(imgBmp, width, height);
                newImg.SetResolution(72, 72);
                var ms = new MemoryStream();
                newImg.Save(ms, System.Drawing.Imaging.ImageFormat.Bmp);
                var bytes = ms.GetBuffer();
                ms.Close();
                return new FileContentResult(bytes, contentTypeStr);
            }
        }

4. 結果如下圖

700px 寬度

200px 寬度