如何渲染图像为pdf（canvas和pdfkit）

Question

我有一个nodejs的功能，从许多图像生成图像，然后生成一个PDF文件。林只用一个形象尝试，但我需要增加更多，但这并不似乎工作

function HelperHandler() { 
    this.pdf = function(req, res, next) { 
    var doc = new PDFDocument; 
    mergeImages(function(err, image) { 
     if (err) 
     return res.json(err); 

     doc.image(image, 100, 100); 
     doc.output(function(string) { 
     res.contentType = "application/pdf"; 
     res.send(string); 
     }); 
    }) 
    } 
} 

var mergeImages = function(callback) { 
    var Canvas = require("canvas") 
    , fs  = require("fs"); 

    fs.readFile(global.root_path + "/images/bg.jpg", function(err, data) { 
    if (err) 
     callback("error loading image"); 
    else { 
     var canvas = new Canvas(408, 939) 
     , img = new Canvas.Image(data); 
     ctx = canvas.getContext("2d"); 
     img.onload = function() { 
     ctx.drawImage(img, 0, 0, 408, 939); 
     } 
     canvas.toDataURL('image/png', function(err, str) { 
     callback(null, str); 
     }); 
    } 
    }); 
} 

错误

Error: ENAMETOOLONG, name too long 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZgAAAOrCAYAAABqSpB/AAAABmJLR0QA/wD/AP+gvaeTAAAF5UlEQVR4nO3BMQEAAADCoPVPbQo/oAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAICjAWckAAHF4EUcAAAAAElFTkSuQmCC' 
    at Object.openSync (fs.js:427:18) 
    at Object.readFileSync (fs.js:284:15) 
    at Function.open (/Users/jtomasrl/code/app/server/node_modules/pdfkit/js/image.js:27:28) 
    at PDFDocument.image (/Users/jtomasrl/code/app/server/node_modules/pdfkit/js/mixins/images.js:27:26) 
    at /Users/jtomasrl/code/app/server/lib/handler/current/helper.js:15:11 
    at /Users/jtomasrl/code/app/server/lib/handler/current/helper.js:41:9 
    at /Users/jtomasrl/code/app/server/node_modules/canvas/lib/canvas.js:217:7 

Answer 1

的错误是因为：

doc.image(image, 100, 100); 

image需求成为文件路径而不是数据网址。

您需要分配临时文件，将画布作为PNG写入该文件，然后将该临时文件的路径名传递至doc.image(path, ...)，然后删除临时文件。

见http://pdfkit.org/docs/images.html

Answer 2

您可以使用a buffer or a path与PDFKit图像。

但是，您不能使用base64 URL，您需要将此字符串解码为缓冲区。

要使用的base64数据：在德的base64 /编码与节点缓存here

doc.image(new Buffer(image.replace('data:image/png;base64,',''), 'base64'), 100, 100); // this will decode your base64 to a new buffer 

更多信息。