Can I convert only selected pages instead of the whole document?

Yes. Each page card in the workspace contains a selection checkbox. You can select specific pages (or use Select All / Deselect All) and click Download Selected as ZIP.

What is the difference between 150 DPI and 300 DPI?

150 DPI provides sharp clarity for desktop displays and smartphones while keeping image file sizes modest. 300 DPI renders ultra-high-resolution images matching professional magazine print quality.

Are my PDF documents uploaded to any remote server?

No. All page rasterization, canvas drawing, and ZIP compilation occurs strictly on your local machine using client-side JavaScript and WebAssembly. Your files remain 100% private.

Can I download an individual page image directly?

Yes. Each page card has its own dedicated Download button allowing you to save that specific page as a standalone JPG or PNG file instantly.

Convert PDF to JPG & PNG High-Res Extraction • ZIP Export

Render PDF pages into crystal-clear JPG or lossless PNG images at 72, 150, or 300 DPI. Download individual pages or export all in a single ZIP.

Zero file upload — processed entirely in your browser memory

ℑ

Select or Drop a PDF File Here

Extract high-res JPG/PNG images • Bulk ZIP export • 100% Private

PDF document.pdf Loading pages...

Image Format

Rendering Resolution

JPEG Quality

Selected: 0 pages

Ready to export images

Processing document...

Comprehensive Technical Guide: PDF Rasterization, DPI Scaling & Canvas Export

Exporting PDF pages into raster image formats (JPEG or PNG) is a complex rendering process known as rasterization. Because PDF documents store typographical fonts as mathematical Bézier splines, vector path curves as infinite-resolution drawing commands, and color profiles as ICC matrices, converting them to a discrete pixel grid requires careful resolution scaling, font hinting, and sub-pixel antialiasing.

1. The Math of DPI Scaling in PDF Rendering

In digital typography and PDF User Space (ISO 32000-1 §8.3), page dimensions are expressed in points, where 1 point is defined as 1/72 of an inch:

A standard US Letter page (8.5 × 11 inches) measures 612 × 792 points.
An ISO A4 page (210 × 297 mm) measures 595.28 × 841.89 points.

When rendering a PDF page to an HTML5 <canvas> via pdf.js, the scaling factor determines the output pixel grid density:

scale = target_DPI / 72.0
canvas.width = Math.floor(page.view[2] * scale)
canvas.height = Math.floor(page.view[3] * scale)

Target DPI	Scale Multiplier	A4 Output Resolution	Best Use Case
72 DPI	1.0×	595 × 842 px	Web thumbnails, rapid preview
150 DPI	2.083×	1240 × 1754 px	High-DPI laptop screens, iPad presentations
300 DPI	4.167×	2480 × 3508 px	Commercial laser printing, archival scans

2. Lossless PNG vs Lossy JPEG Compression

Choosing the appropriate image format depends directly on document content:

PNG (Portable Network Graphics): Applies 2D predictive filtering followed by DEFLATE compression. Ideal for text documents, CAD schematics, and UI mockups where crisp text edges and white backgrounds must not exhibit compression halos or color fringing.
JPEG (Joint Photographic Experts Group): Applies Discrete Cosine Transform (DCT) block quantization. Excellent for photographic brochures and magazine scans, reducing file size by 70% to 85% compared to PNG while retaining visual fidelity.

3. The Internal Structure of PKZIP Archives

When downloading multiple pages simultaneously, initiating dozens of separate HTTP download triggers often causes browser popup blockers to flag the request. QuickCoderHub circumvents this by packaging all generated image blobs into a single compliant .zip file using an in-memory pure JavaScript PKZIP implementation conforming to PKWARE APPNOTE.TXT.

A compliant ZIP archive comprises three consecutive binary data sections:

Local File Headers (0x04034b50): Precedes each individual image payload, encoding uncompressed file size, CRC-32 checksum, filename bytes, and compression method (Method 0: Store).
Central Directory Record (0x02014b50): Stored at the end of the archive, cataloging file offsets, attributes, and file names for rapid random-access extraction by decompression software (such as WinZip, 7-Zip, or macOS Archive Utility).
End of Central Directory Record (0x06054b50): A 22-byte termination trailer detailing total disk entries and central directory byte length.

4. Multi-Threading and Web Workers

Rasterizing high-resolution 300 DPI pages demands significant computational throughput. QuickCoderHub offloads rendering tasks to a dedicated Web Worker running pdf.worker.min.js. This multithreaded architecture guarantees that the browser user interface remains silky-smooth and fully responsive with real-time progress bar feedback, even while rendering multi-megabyte CAD blueprints.

Frequently Asked Questions

Can I convert only selected pages instead of the whole document?: Yes. Each page card in the workspace contains a selection checkbox. You can select specific pages (or use "Select All" / "Deselect All") and click "Download Selected as ZIP".
What is the difference between 150 DPI and 300 DPI?: 150 DPI provides sharp clarity for desktop displays and smartphones while keeping image file sizes modest (approx. 500 KB per page). 300 DPI renders ultra-high-resolution images (approx. 8.7 megapixels per page) matching professional magazine print quality.
Are my PDF documents uploaded to any remote server?: No. All page rasterization, canvas drawing, and ZIP compilation occurs strictly on your local machine using client-side JavaScript and WebAssembly. Your files remain 100% private.
Can I download an individual page image directly?: Yes. Each page card has its own dedicated "Download" button allowing you to save that specific page as a standalone JPG or PNG file instantly.