如何使用NodeJS imagemagick库将PD​​F的首页转换为JPG? [英] How can I convert the first page of a PDF to a JPG using the NodeJS imagemagick library?

问题描述

我正在尝试将pdf文件转换为预览图标jpg 对NodeJS使用imagemagick库.我在尝试着 仅生成首页(用于多页pdf)的预览.

I am attempting to convert pdf files into a preview icon jpg using the imagemagick library for NodeJS. I am trying to generate a preview of only the first page (for multi-page pdfs).

在普通的命令行imagemagick程序中，这可以是 只需说出转换file.pdf [0] file.jpg"
[0]告诉它仅转换第一页.

In the normal command line imagemagick program this can be done easily by saying "convert file.pdf[0] file.jpg"
where the [0] tells it to only convert the first page.

但是，我不确定如何使用此库. 我尝试将[0]连接到文件名，但这只是 读取它作为真实文件名的一部分.任何人都知道 使用此库解决此问题的方法?

However I am not sure how to do that with this library. I tried concatenating [0] to the filename, but it just reads it as part of the real file name. Anyone know of a way around this using this library?

我环顾了一会儿，发现了这个，但是 他们没有使用这个库. 将PDF转换为PNG Node.JS

I had a look around for a while and found this, but they are not using this library. Convert PDF to PNG Node.JS

我正在使用的特定库位于: https://www.npmjs.com/package /imagemagick

The specific library I am using is located here: https://www.npmjs.com/package/imagemagick

我正在使用的代码如下:

The code I am working with is below:

            let path = '/tmp/';
            let pageNumber = '[0]';
            let filePath =  path + fileId + fileName + pageNumber; 
            let imgFilePath = path + fileId + '.jpg';
            let writeStream = fs.createWriteStream(filePath);
            writeStream.on('error',err => {
              reject(err);
            });
            stream.pipe(writeStream);


              im.convert([
                filePath,
                '-background','white',
                '-alpha','remove',
                '-resize','192x192',
                '-quality','100',
                imgFilePath
              ],

推荐答案

问题是在进行转换之前，您将 [0] 部分连接到了文件名上.您应该在转换函数的范围内将 [0] 连接起来，如下所示:

The problem is that you are concatenating the [0] part onto the filename before you do the conversion. You should concatenate the [0] within the scope of the convert function like this:

            let path = '/tmp/';
            let filePath =  path + fileId + fileName;
            let imgFilePath = path + fileId + '.jpg';
            let writeStream = fs.createWriteStream(filePath);
            writeStream.on('error',err => {
              reject(err);
            });
            stream.pipe(writeStream);


              im.convert([
                filePath + '[0]',
                '-background','white',
                '-alpha','remove',
                '-resize','192x192',
                '-quality','100',
                imgFilePath
              ], 

此解决方案经过测试可正常工作.

This solution is tested working.

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