要完成@Hossam Barakat 的答案，您可以使用Microsoft ASP.NET Core JavaScript Services 在运行时从 .NET 代码调用任意 NPM 包，这意味着您可以选择任何提供图像缩放的 npm 包并调用它。
该示例使用sharp 模块，该模块有很多依赖项。如果您像我一样喜欢使用纯 javascript 的jimp：
Startup.cs
public class Startup
{
...
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
// Enable Node Services
services.AddNodeServices();
...
}
...
}
ImageController.cs
using System;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.NodeServices;
using Microsoft.AspNetCore.StaticFiles;
using System.Security.Cryptography;
using System.Text;
namespace NodeServicesExamples.Controllers
{
public class ResizeImageController : Controller
{
private const int MaxDimension = 1000;
private static string[] AllowedMimeTypes = new[] { "image/jpeg", "image/png", "image/gif" };
private IHostingEnvironment _environment;
private INodeServices _nodeServices;
public ResizeImageController(IHostingEnvironment environment, INodeServices nodeServices)
{
_environment = environment;
_nodeServices = nodeServices;
}
[Route("resize/{*imagePath}")]
[ResponseCache(Duration = 3600)]
public async Task<IActionResult> Index(string imagePath, double maxWidth, double maxHeight)
{
// Validate incoming params
if (maxWidth < 0 || maxHeight < 0 || maxWidth > MaxDimension || maxHeight > MaxDimension
|| (maxWidth + maxHeight) == 0)
{
return BadRequest("Invalid dimensions");
}
var mimeType = GetContentType(imagePath);
if (Array.IndexOf(AllowedMimeTypes, mimeType) < 0)
{
return BadRequest("Disallowed image format");
}
// Locate source image on disk
var fileInfo = _environment.WebRootFileProvider.GetFileInfo(imagePath);
if (!fileInfo.Exists)
{
return NotFound();
}
var eTag = GenerateETag(Encoding.UTF8.GetBytes($"{fileInfo.LastModified.ToString("s")}-{fileInfo.Length}"));
HttpContext.Response.Headers["ETag"] = eTag;
var match = HttpContext.Request.Headers["If-None-Match"].FirstOrDefault();
if (eTag == match)
{
return StatusCode(304);
}
// Invoke Node and pipe the result to the response
var imageStream = await _nodeServices.InvokeAsync<Stream>(
"./Node/resizeImage",
fileInfo.PhysicalPath,
mimeType,
maxWidth,
maxHeight);
return File(imageStream, mimeType, fileInfo.Name);
}
private string GetContentType(string path)
{
string result;
return new FileExtensionContentTypeProvider().TryGetContentType(path, out result) ? result : null;
}
private string GenerateETag(byte[] data)
{
string ret = string.Empty;
using (var md5 = MD5.Create())
{
var hash = md5.ComputeHash(data);
string hex = BitConverter.ToString(hash);
ret = hex.Replace("-", "");
}
return ret;
}
}
}
节点\resizeImage.js
var jimp = require("jimp");
module.exports = function (result, physicalPath, mimeType, maxWidth, maxHeight) {
// Invoke the 'jimp' NPM module, and have it pipe the resulting image data back to .NET
jimp.read(physicalPath).then(function (file) {
var width = maxWidth || jimp.AUTO;
var height = maxHeight || jimp.AUTO;
file.resize(maxWidth, height)
.getBuffer(mimeType, function (err, buffer) {
var stream = result.stream;
stream.write(buffer);
stream.end();
});
}).catch(function (err) {
console.error(err);
});
};
安装 jimp：npm install jimp --save