pdf-img-convert/README.md

A simple module to convert PDF files into image buffers (without filesystem usage)

# pdf-img-convert.js
**A lightweight JavaScript package for converting PDFs into images,
built on Mozilla's powerful [PDF.js](https://github.com/mozilla/pdf.js) library.**

## Motivation

While there are numerous JavaScript solutions for converting PDFs, many rely heavily on the filesystem by creating temporary files and using non-native binaries like Ghostscript.

This solution simplifies the process by exclusively using JavaScript arrays, significantly streamlining the pipeline and, ideally, enhancing performance.

## Installation

```bash
npm install pdf-img-convert
```

## Usage

The package by default returns an `Array` of `Uint8Array` objects,
each of which represents an image encoded in png format or a base64-encoded image output if required

Here are some examples of how to use the module. First, make sure to import it

```javascript
const pdf2img = await import("pdf-img-convert");
```
The package provides a single function, convert, which accepts the following PDF formats as input:

* URL of a PDF (e.g., www.example.com/sample.pdf)

* Path to a local PDF file (e.g., ./examples/sample.pdf)

* A `Buffer` object containing PDF data

* A `Uint8Array` object containing PDF data

* Base64-encoded PDF data

**Note: The convert function is asynchronous and returns a `Promise` object.**

The output can be manipulated using the `conversion_config` argument mentioned below.

Here's an example of how to use it in synchronous code, `uint8arrays` as the default output:

```javascript
import fs from 'fs';
import path from 'path';

async function processPDFs() {
    const pdf2img = await import("pdf-img-convert");

    // Both HTTP, HTTPS, and local paths are supported
    const outputWithExternalLink = await pdf2img.convert('https://sedl.org/afterschool/toolkits/science/pdf/ast_sci_data_tables_sample.pdf');
    const outputWithLocalSample = await pdf2img.convert('./test_pdfs/sample.pdf');

    // OUTPUT OPTIONS ARRAY
    const outputs = [outputWithExternalLink, outputWithLocalSample];
    
    const pdfArray = outputs[0]; // Change the index to select different outputs

    function saveImages(pdfArray) {
        pdfArray.forEach((image, index) => {
            const outputPath = path.join('./outputImages', `saveImages_${index}.png`);
            fs.writeFile(outputPath, image, (error) => {
                if (error) {
                    console.error(`Error saving image ${index + 1}:`, error);
                } else {
                    console.log(`Image ${index + 1} saved successfully`);
                }
            });
        });
    }
    // Call the function to save images
    saveImages(pdfArray);
}
// Call the async function
processPDFs();
```

Here's an example of how to use it in synchronous code, `base64-encoded` output as the chosen option:
```javascript
import fs from 'fs';
import path from 'path';

let config = {
    base64: true,
    scale: 2
};
async function processPDF() {
    const pdf2img = await import("pdf-img-convert");
    const outputWithLocalSampleAndConfig = await pdf2img.convert('./examples/example.pdf', config);
    const pdfArray = outputWithLocalSampleAndConfig;
    function saveBase64Images(pdfArray) {
        console.log('Processing base64Images...');
        pdfArray.forEach((base64Data, index) => {
            // Convert Base64 string to binary buffer
            const buffer = Buffer.from(base64Data, 'base64');
            // Define an output path
            const outputPath = path.join('./outputImages', `saveBase64Image_${index}.png`);
            // Write the buffer to a PNG file
            fs.writeFile(outputPath, buffer, (error) => {
                if (error) {
                    console.error(`Error saving image ${index + 1} (base64):`, error);
                } else {
                    console.log(`Image ${index + 1} (base64) saved successfully`);
                }
            });
        });
    }
    // Example usage: call this function with the Base64 array
    saveBase64Images(pdfArray);
}
// Call the async function
processPDF();
```

Here's an example of how to use it in Next.js api folder, `base64-encoded` output as the chosen option:

*Ensure you have a dotenv file with `ROOT_PATH` pointing to your root directory*

```dotenv 
ROOT_PATH=./
```

*You have a `/public/uploads directory` in the root entry of your project, if not create it.*


```javascript
import path from "path";
import fs from "fs";

const UPLOAD_DIR = path.resolve(process.env.ROOT_PATH ?? "", "public/uploads");

/*SHARP ENHANCEMENT*/
const writeToDir = async (imageData, fileName, filePath) => {
    try {
        await fs.promises.writeFile(filePath, imageData);
        console.log(`Image processed and saved successfully: ${filePath}`);
        return {
            fileName: fileName,
            filePath: filePath
        };
    } catch (error) {
        console.error("Error processing the image:", error);
        return null;
    }
};
export const POST = async (req: NextRequest) => {
    const pdf2img = await import("pdf-img-convert");
    const formData = await req.formData();
    const pdfFiles = []
    const convertedImages = []

    // Loop over the FormData content
    for (const [key, value] of formData.entries()) {
        if (value instanceof Blob) {
            if (key === "pdfFiles") {
                pdfFiles.push(value);
            }
        }
    }
    // check for file uploads
    if (pdfFiles.length === 0) {
        return NextResponse.json({
            success: false,
            message: "No files uploaded"
        });
    }
    for (const file of pdfFiles) {
        const pdfBuffer = Buffer.from(await file.arrayBuffer());
        const imagePages = await pdf2img.convert(pdfBuffer, { base64: true }); // Ensure base64 is true to get Base64 data

        for (let i = 0; i < imagePages.length; i++) {
            const imageData = imagePages[i];
            const base64Data = imageData.replace(/^data:image\/\w+;base64,/, ""); // Remove Base64 header
            const imageBuffer = Buffer.from(base64Data, "base64"); // Convert Base64 to Buffer

            const fileName = `${path.basename(file.name, path.extname(file.name))}_page_${i + 1}.png`;
            const filePath = path.join(UPLOAD_DIR, fileName);

            const writeFile = await writeToDir(imageBuffer, fileName, filePath);
            if (writeFile) {
                convertedImages.push(writeFile);
            }
        }
    }
    // if successfully
    return NextResponse.json({
        success: true,
        message: "Files uploaded successfully",
    });
}
```
Here is how to fetch single or multiple PDF documents from the client side using a `.jsx or .tsx` component:

*In this case my `api` route points to `/app/api/pdf2img`, you can change it to suite your own naming*

```jsx
"use client";
import React, { useRef, useState } from "react";
export default function PDFUploader() {
    const MAX_FILES = 4;
    const [fileNames, setFileNames] = useState([]);
    const [pdfFiles, setPdfFiles] = useState([]);
    const [errorMessage, setErrorMessage] = useState("");
    const fileInputRef = useRef(null);

    const handleFileChange = (e) => {
        const files = Array.from(e.target.files);
        if (files.length > MAX_FILES) {
            setErrorMessage(`You can only upload a maximum of ${MAX_FILES} files.`);
            clearStates();
        } else {
            const names = files.map((file) => file.name);
            const pdfs = files.filter(file => file.type === "application/pdf");
            setStates(pdfs, names);
        }
    };

    const handleSubmit = async (e) => {
        e.preventDefault();
        if (pdfFiles.length === 0) {
            setErrorMessage("No PDF files selected.");
            return;
        }
        try {
            const formData = new FormData();
            pdfFiles.forEach((file) => {
                formData.append("pdfFiles", file); // Key is "pdfFiles"
            });

            const response = await fetch("/api/pdf2img", {
                method: "POST",
                body: formData
            });

            const result = await response.json();
            if (result.success) {
                clearStates();
                alert(`Upload successful: ${result.message}`);
            } else {
                alert(`Upload failed: ${result.message}`);
            }
        } catch (error) {
            console.error("Upload error:", error);
            alert("An error occurred during upload.");
        }
    };

    const clearStates = () => {
        setFileNames([]);
        setPdfFiles([]);
        if (fileInputRef.current) {
            fileInputRef.current.value = ""; // Reset the file input via ref
        }
    };

    const setStates = (pdfs, names) => {
        setPdfFiles(pdfs);
        setFileNames(names);
    };

    return (
        <html>
        <body style={{padding:0, left: 0}}>
        <form onSubmit={handleSubmit}>
            <input
                ref={fileInputRef}
                onChange={handleFileChange}
                type="file"
                name="fileUpload"
                multiple
                accept=".pdf"
            />
            <button type="submit">Submit</button>
        </form>
        {errorMessage && (
            <div>
                <p style={{ textAlign: "center", color: "red" }}>{errorMessage}</p>
            </div>
        )}
        </body>
        </html>
    );
}
```

There is also an optional second `conversion_config` argument which accepts an object like this:
```javascript
{
  width: 100 //Number in px
  height: 100 // Number in px
  scale: 2
  page_numbers: [1, 2, 3] // A list of pages to render instead of all of them
  base64: true
}
```
The following attributes are optional and can be omitted from the configuration object:

* `width` or `height`: Controls the scale of the output images. If both are provided, only width will be used, and height will be ignored.

* `page_numbers`: Specifies which pages to render. Pages are 1-indexed.

* `base64`: Set to true to receive base64-encoded image output. If omitted or set to false, the output will be an array of Uint8Arrays.

* `scale`: Defines the viewport scale ratio, defaulting to 1 (original width and height).

## Contributing

If you'd like to contribute, please do submit a pull request!

Once you've finalised your changes, please include a summary of these changes under the `[Unreleased]` section of `CHANGELOG.md` in [this](https://keepachangelog.com/en/1.0.0/) format.