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docs: Improve main code samples (#105)
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@adrienjoly
adrienjoly authored Mar 25, 2022
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Showing 1 changed file with 78 additions and 106 deletions.
184 changes: 78 additions & 106 deletions README.md
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Expand Up @@ -17,10 +17,12 @@ Summary:

## Installation, tests and CLI usage (make sure node v8 or v10)

npm install pdfreader
cd node_modules/pdfreader
npm test
node parse.js test/sample.pdf
```sh
npm install pdfreader
cd node_modules/pdfreader
npm test
node parse.js test/sample.pdf
```

## Raw PDF reading

Expand All @@ -42,9 +44,11 @@ It's up to your callback to process these items into a data structure of your ch
For example:

```javascript
new PdfReader().parseFileItems("sample.pdf", function (err, item) {
if (err) callback(err);
else if (!item) callback();
const { PdfReader } = require("pdfreader");

new PdfReader().parseFileItems("test/sample.pdf", (err, item) => {
if (err) console.error("error:", err);
else if (!item) console.warn("end of file");
else if (item.text) console.log(item.text);
});
```
Expand All @@ -54,12 +58,14 @@ new PdfReader().parseFileItems("sample.pdf", function (err, item) {
As above, but reading from a buffer in memory rather than from a file referenced by path. For example:

```javascript
var fs = require("fs");
fs.readFile("sample.pdf", (err, pdfBuffer) => {
const fs = require("fs");
const { PdfReader } = require("pdfreader");

fs.readFile("test/sample.pdf", (err, pdfBuffer) => {
// pdfBuffer contains the file content
new PdfReader().parseBuffer(pdfBuffer, function (err, item) {
if (err) callback(err);
else if (!item) callback();
new PdfReader().parseBuffer(pdfBuffer, (err, item) => {
if (err) console.error("error:", err);
else if (!item) console.warn("end of buffer");
else if (item.text) console.log(item.text);
});
});
Expand All @@ -68,86 +74,50 @@ fs.readFile("sample.pdf", (err, pdfBuffer) => {
### Example: reading from a buffer of an online PDF

```javascript
const https = require("https");
const pdfreader = require("pdfreader");

async function bufferize(url) {
var hn = url.substring(url.search("//") + 2);
hn = hn.substring(0, hn.search("/"));
var pt = url.substring(url.search("//") + 2);
pt = pt.substring(pt.search("/"));
const options = { hostname: hn, port: 443, path: pt, method: "GET" };
return new Promise(function (resolve, reject) {
var buff = new Buffer.alloc(0);
const req = https.request(options, (res) => {
res.on("data", (d) => {
buff = Buffer.concat([buff, d]);
});
res.on("end", () => {
resolve(buff);
});
});
req.on("error", (e) => {
console.error("https request error: " + e);
});
req.end();
});
const get = (url) =>
new Promise((resolve, reject) =>
https
.get(url, (res) => {
const data = [];
res
.on("data", (chunk) => data.push(chunk))
.on("end", () => resolve(Buffer.concat(data)));
})
.on("error", reject)
);

function addTextToLines(textLines, item) {
const existingLine = textLines.find(({ y }) => y === item.y);
if (existingLine) {
existingLine.text += " " + item.text;
} else {
textLines.push(item);
}
}

/*
if second param is set then a space ' ' inserted whenever text
chunks are separated by more than xwidth
this helps in situations where words appear separated but
this is because of x coords (there are no spaces between words)
each page is a different array element
*/
async function readlines(buffer, xwidth) {
return new Promise((resolve, reject) => {
var pdftxt = new Array();
var pg = 0;
new pdfreader.PdfReader().parseBuffer(buffer, function (err, item) {
if (err) console.log("pdf reader error: " + err);
const parseLinesPerPage = (buffer) =>
new Promise((resolve, reject) => {
const linesPerPage = [];
let pageNumber = 0;
new PdfReader().parseBuffer(buffer, (err, item) => {
if (err) reject(err);
else if (!item) {
pdftxt.forEach(function (a, idx) {
pdftxt[idx].forEach(function (v, i) {
pdftxt[idx][i].splice(1, 2);
});
});
resolve(pdftxt);
} else if (item && item.page) {
pg = item.page - 1;
pdftxt[pg] = [];
resolve(linesPerPage.map((page) => page.map((line) => line.text)));
} else if (item.page) {
pageNumber = item.page - 1;
linesPerPage[pageNumber] = [];
} else if (item.text) {
var t = 0;
var sp = "";
pdftxt[pg].forEach(function (val, idx) {
if (val[1] == item.y) {
if (xwidth && item.x - val[2] > xwidth) {
sp += " ";
} else {
sp = "";
}
pdftxt[pg][idx][0] += sp + item.text;
t = 1;
}
});
if (t == 0) {
pdftxt[pg].push([item.text, item.y, item.x]);
}
addTextToLines(linesPerPage[pageNumber], item);
}
});
});
}

(async () => {
var url =
"https://www.w3.org/TR/2011/NOTE-WCAG20-TECHS-20111213/working-examples/PDF2/bookmarks.pdf";
var buffer = await bufferize(url);
var lines = await readlines(buffer);
lines = await JSON.parse(JSON.stringify(lines));
console.log(lines);
})();
const url = new URL(
"https://raw.githubusercontent.com/adrienjoly/npm-pdfreader/master/test/sample.pdf"
);
const buffer = get(url)
.then((buffer) => parseLinesPerPage(buffer))
.then((linesPerPage) => console.log(linesPerPage));
```

### Example: parsing lines of text from a PDF file
Expand All @@ -157,30 +127,31 @@ async function readlines(buffer, xwidth) {
Here is the code required to convert this PDF file into text:

```js
var pdfreader = require("pdfreader");
const { PdfReader } = require("pdfreader");

var rows = {}; // indexed by y-position
let rows = {}; // indexed by y-position

function printRows() {
function flushRows() {
Object.keys(rows) // => array of y-positions (type: float)
.sort((y1, y2) => parseFloat(y1) - parseFloat(y2)) // sort float positions
.forEach((y) => console.log((rows[y] || []).join("")));
rows = {}; // clear rows for next page
}

new pdfreader.PdfReader().parseFileItems(
"CV_ErhanYasar.pdf",
function (err, item) {
if (!item || item.page) {
// end of file, or page
printRows();
console.log("PAGE:", item.page);
rows = {}; // clear rows for next page
} else if (item.text) {
// accumulate text items into rows object, per line
(rows[item.y] = rows[item.y] || []).push(item.text);
}
new PdfReader().parseFileItems("test/sample.pdf", (err, item) => {
if (err) {
console.error({ err });
} else if (!item) {
flushRows();
console.log("END OF FILE");
} else if (item.page) {
flushRows(); // print the rows of the previous page
console.log("PAGE:", item.page);
} else if (item.text) {
// accumulate text items into rows object, per line
(rows[item.y] = rows[item.y] || []).push(item.text);
}
);
});
```

Fork this example from [parsing a CV/résumé](https://github.com/adrienjoly/npm-pdfreader-example).
Expand Down Expand Up @@ -235,10 +206,10 @@ Fork this example from [parsing a CV/résumé](https://github.com/adrienjoly/npm

```javascript
new PdfReader({ password: "YOUR_PASSWORD" }).parseFileItems(
"sample-with-password.pdf",
"test/sample-with-password.pdf",
function (err, item) {
if (err) callback(err);
else if (!item) callback();
if (err) console.error(err);
else if (!item) console.warn("end of file");
else if (item.text) console.log(item.text);
}
);
Expand All @@ -253,7 +224,7 @@ Rule instances expose "accumulators": methods that defines the data extraction s
Example:

```javascript
var processItem = Rule.makeItemProcessor([
const processItem = Rule.makeItemProcessor([
Rule.on(/^Hello \"(.*)\"$/)
.extractRegexpValues()
.then(displayValue),
Expand All @@ -265,8 +236,9 @@ var processItem = Rule.makeItemProcessor([
.accumulateAfterHeading()
.then(displayValue),
]);
new PdfReader().parseFileItems("sample.pdf", function (err, item) {
processItem(item);
new PdfReader().parseFileItems("test/sample.pdf", (err, item) => {
if (err) console.error(err);
else processItem(item);
});
```

Expand Down

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