如何解决附加 Blob 未正确连接 pdf 页面
我正在使用 Azure 存储将一些 pdf 存储为 blob。我想使用用于 Azure 存储的 Node SDK 中提供的 AppendBlob class
动态连接它们。我的问题是,即使合并后的 pdf 大小正确,当我打开它时,它也只显示其中的最后一页,而不是我连接的所有页面。我在代码中犯了错误吗?如果您对此问题有任何见解,我将不胜感激。
我不想下载它们并将它们连接到代码中,因为在某些情况下,生成的 pdf 大小超过 2gb,节点无法处理。
let bundleUuid = uuidv4();
var connString = process.env.ST_ENV_01_APS_03_CONNECTION_STRING;
var appendBlobClient = new AppendBlobClient(connString,container,userId + "/bundles/" + bundleUuid + ".pdf");
await appendBlobClient.create();
context.log(userId + "/bundles/" + bundleUuid + ".pdf");
for (const basketDocumentUri of basketDocumentUris) {
context.log("Fetching: " + basketDocumentUri.document_uuid + "/" + (basketDocumentUri.page_index + 1) + ".pdf")
let bbc = await containerClient.getBlockBlobClient(basketDocumentUri.document_uuid
+ "/" + (basketDocumentUri.page_index + 1) + ".pdf");
let details = await bbc.getProperties();
let url = self.generateSasTokenPDF(basketDocumentUri.document_uuid + "/"
+ (basketDocumentUri.page_index + 1) + ".pdf","r");
try {
let mbblk = 4194304
let offset = 0;
while(offset < details.contentLength){
let response = await appendBlobClient.appendBlockFromURL(url.uri,offset,mbblk);
context.log(response);
offset += mbblk;
context.log(offset);
}
} catch (error) {
context.log(error);
debugger;
}
}
callback(bundleUuid)
解决方法
正如 Gaurav 在评论中所说,简单地将字节附加到现有的 blob 会使 PDF 文件的格式无效。 不可能与文件交互而不将它们下载到某处。
以下是将 blob 下载到缓冲区:
const containerClient = blobServiceClient.getContainerClient(containerName);
const blobClient = containerClient.getBlobClient(blobName);
// Get blob content from position 0 to the end
// In Node.js,get downloaded data by accessing downloadBlockBlobResponse.readableStreamBody
const downloadBlockBlobResponse = await blobClient.download();
const downloaded = (
await streamToBuffer(downloadBlockBlobResponse.readableStreamBody)
).toString();
console.log("Downloaded blob content:",downloaded);
// [Node.js only] A helper method used to read a Node.js readable stream into a Buffer
async function streamToBuffer(readableStream) {
return new Promise((resolve,reject) => {
const chunks = [];
readableStream.on("data",(data) => {
chunks.push(data instanceof Buffer ? data : Buffer.from(data));
});
readableStream.on("end",() => {
resolve(Buffer.concat(chunks));
});
readableStream.on("error",reject);
});
}
使用 HummusJS 合并 PDF:
const hummus = require('hummus');
const memoryStreams = require('memory-streams');
/**
* Concatenate two PDFs in Buffers
* @param {Buffer} firstBuffer
* @param {Buffer} secondBuffer
* @returns {Buffer} - a Buffer containing the concactenated PDFs
*/
const combinePDFBuffers = (firstBuffer,secondBuffer) => {
var outStream = new memoryStreams.WritableStream();
try {
var firstPDFStream = new hummus.PDFRStreamForBuffer(firstBuffer);
var secondPDFStream = new hummus.PDFRStreamForBuffer(secondBuffer);
var pdfWriter = hummus.createWriterToModify(firstPDFStream,new hummus.PDFStreamForResponse(outStream));
pdfWriter.appendPDFPagesFromPDF(secondPDFStream);
pdfWriter.end();
var newBuffer = outStream.toBuffer();
outStream.end();
return newBuffer;
}
catch(e){
outStream.end();
throw new Error('Error during PDF combination: ' + e.message);
}
};
combinePDFBuffers(PDFBuffer1,PDFBuffer2);
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 dio@foxmail.com 举报,一经查实,本站将立刻删除。