.net core 接口返回图片并且进行压缩
步骤:
1. 新建.net core 2.0 项目(过程略)
2. 通过nuget添加引用 System.Drawing.Common; .net core 开始的时候并没有System.Drawing,在2.0之后新增了 System.Drawing.Common,用于替代原来的System.Drawing.用法基本一致
3. 写接口了
a. 使用特性路由传入想要的尺寸和文件名,这样可以更好的用于前端展示,
b. 没有找到图片或者错误时返回默认的一张图片
c. 需要注意引用 using System.IO;using System.Drawing;
d. .net core 中返回图片不用 HttpResponseMessage 类型,而是直接采用 IActionResult. 而且封装了FileContentResult类,可以直接返回.
e. .net core 中获取当前项目的物理地址可以通过 AppContext.BaseDirectory 和.net 有区别
/// <summary>
/// 访问图片
/// </summary>
/// <param name="width">所访问图片的宽度,高度自动缩放,大于原图尺寸或者小于等于0返回原图</param>
/// <param name="name">所要访问图片的名称或者相对地址</param>
/// <returns>图片</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";//没有找到图片
var imgPath = string.IsNullOrEmpty(name) ? errorImage : appPath + name;
//获取图片的返回类型
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();
//未知的图片类型
if (!contentTypDict.ContainsKey(imgType))
{
imgPath = errorImage;
}
else
{
contentTypeStr = contentTypDict[imgType];
}
//图片不存在
if (!new FileInfo(imgPath).Exists)
{
imgPath = errorImage;
}
//原图
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);
}
}
//缩小图片
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);
}
}
