跨平台的NodeJS 组件如何解决.NetCore不支持System.Drawing图形功能的若干问题
这篇文章给大家介绍跨平台的NodeJS 组件如何解决.NetCore不支持System.Drawing图形功能的若干问题，内容非常详细，感兴趣的小伙伴们可以参考借鉴，希望对大家能有所帮助。
问题
生成缩略图
生成验证码
生成二维码
给图片加水印
外部引用
Node 不解释 https://nodejs.org/en/download/
sharp 高性能缩略图 https://github.com/lovell/sharp
qr-image 二维码 https://github.com/alexeyten/qr-image
captchagen 验证码 https://github.com/contra/captchagen
node-images 轻量级跨平台图像编解码库 https://github.com/zhangyuanwei/node-images
生成缩略图代码
resizeImage.js
var sharp = require('sharp');
module.exports = function (result, physicalPath, mimeType, maxWidth, maxHeight) {
// Invoke the 'sharp' NPM module, and have it pipe the resulting image data back to .NET
sharp(physicalPath)
.resize(maxWidth || null, maxHeight || null)
.pipe(result.stream);
}
ResizeController.cs
public class ResizeController : Controller
{
private const int MaxDimension = 1000;
private static string[] AllowedMimeTypes = new[] { "image/jpeg", "image/png", "image/gif" };
private IHostingEnvironment _environment;
private INodeServices _nodeServices;
public ResizeController(IHostingEnvironment environment, INodeServices nodeServices)
{
_environment = environment;
_nodeServices = nodeServices;
}
[Route("resize_{maxWidth}_{maxHeight}/{*imagePath}")]
public async Task
{
imagePath = imagePath;
// 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();
}
// Invoke Node and pipe the result to the response
var imageStream = await _nodeServices.InvokeAsync
"./Node/resizeImage",
fileInfo.PhysicalPath,
mimeType,
maxWidth,
maxHeight);
return File(imageStream, mimeType);
}
private string GetContentType(string path)
{
string result;
return new FileExtensionContentTypeProvider().TryGetContentType(path, out result) ? result : null;
}
}
效果
生成验证码代码
captchagen.js
var captchagen = require('captchagen');
module.exports = function (result, width, height, text) {
// optional object arg with keys: height, width, text, font
var captcha = captchagen.create({ width: width, height: height, text: text||'8888'});
captcha.generate(); // Draws the image to the canvas
/* call `generate()` before running the below */
captcha.stream().pipe(result.stream); // outputs an image stream. type can be either png or jpeg (png is the default)
}
效果
生成二维码代码
1 var qr = require('qr-image');
2 module.exports = function (result, size, url) {
3 qr.image(url, { type: 'png', size: size, margin: 1 })
4 .pipe(result.stream);
5 }效果
安装Node引用组件时费了不少时间主要是因为没细看作者给出的各种环境下的安装说明。
加水印目前还没做好，主要是要修改源码实现支持stream类型输出
抛砖引玉，希望更多朋友分享 Node各种组件的应用.
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