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Images to PDF

How to convert images to PDF without losing quality

By DeckleUpdated

To convert images to PDF without losing quality, use PNG to PDF for PNG files and JPG to PDF for JPG files, then choose Create PDF. PNG pages are stored losslessly and JPEGs are copied into the PDF byte for byte, so neither is re-compressed while the image is within your device's pixel limit. HEIC and TIFF images are the exception: they are re-encoded as high-quality JPEG.

PNG to PDF

Choose a source for the job

Photograph

Inspect colour and detail

Diagram

Inspect lines and labels

Scan

Inspect frames and text

A static PDF page does not preserve motion

Conceptual illustration · image format and output page behaviour are separate decisions.

How to convert images to PDF at full quality with Deckle

  1. Keep the images in the format they were made in. Do not save a PNG as JPG, or a JPG again, before converting.
  2. Open PNG to PDF for PNG files or JPG to PDF for JPG files, and choose Select files, or drop the images onto the page.
  3. Put the images in order with the up and down arrows.
  4. Choose a Page size. Match each image keeps one pixel per point; Fit inside A4 draws large images smaller on the page but keeps every pixel.
  5. Choose Create PDF and download the PDF.
  6. Zoom in to 200% or more on fine detail, such as small text or thin lines, and compare it with the original image.

The result screen says how many pages were created, and its checks confirm that the PDF reopens with every planned page at the planned size.

What happens to each format

Format How it goes into the PDF Quality
JPG The JPEG data is copied in unchanged Identical to the file
PNG Pixels are kept exactly and compressed losslessly Identical pixels
HEIC Decoded, then saved as JPEG at quality 90 Very close; fine detail can change slightly
TIFF Each frame decoded, then saved as JPEG at quality 90 Very close; crisp black-and-white text can soften slightly

Deckle embeds JPEG and PNG data directly. A PDF cannot hold HEIC data at all, and TIFF files come in many internal layouts, so both are decoded first and the decoded pixels are saved as JPEG. Quality 90 is high: photos look the same at normal zoom, and differences appear only when you zoom far in on sharp edges.

Why page size does not lower quality

Choosing Fit inside A4 often worries people because the image looks smaller. Shrinking only changes the size the image is drawn at on the page. The PDF still holds every pixel of the original, so zooming in shows full detail and printing uses all of it. Deckle never downsamples, crops or enlarges an image.

Match each image maps one pixel to one point. A 3000 × 2000 pixel image becomes a 3000 × 2000 pt page, about 42 × 28 inches. The detail is the same either way; only the page size differs.

Quality problems that come from the source

A PDF cannot be sharper than the image you give it. If the PDF looks soft, check the original first.

  • A JPG that was saved many times. Every save of a JPEG loses a little more detail. Use the earliest copy you have, ideally straight from the camera or export.
  • A screenshot saved as JPG. JPEG blurs the edges of text. Take the screenshot again as PNG.
  • A small image. A 600-pixel-wide image only has 600 pixels of detail, however you convert it. Export a larger version from its source.
  • A photo sent through a messaging app. Many messaging apps shrink photos. Ask for the original file instead.

For more on why JPEG suits photos but not text, see JPG compression and text edges. For diagrams and line art, see why PNG suits line art.

Keep HEIC and TIFF as sharp as possible

For iPhone photos, HEIC to PDF's quality-90 JPEG is visually the same as the photo at normal zoom. If you need a JPG copy anyway, there is no gain in exporting JPG from your photo app first and then using JPG to PDF: that is still one HEIC-to-JPEG step. HEIC to PDF or JPEG first compares the two routes.

For black-and-white TIFF scans where every edge matters, such as engineering drawings, save the TIFF as PNG in an image editor and use PNG to PDF, which keeps the pixels exactly.

Tips

  • Prefer PNG for anything with text. Screenshots, scanned text and diagrams stay crisp as PNG.
  • Expect the PDF to be about as large as the images. Lossless means no size saving; twenty 4 MB photos give a PDF of about 80 MB.
  • Check transparency. PNG transparency is kept. HEIC and TIFF transparency becomes white.
  • Watch the pixel limit. Each page keeps up to 16 megapixels on a computer or Android device, and 4 megapixels on iPhone and iPad. A larger image is scaled down to fit, and a scaled JPEG is re-saved at quality 90, so convert large photos on a computer. The review lists every image that will be scaled before you convert.

Frequently asked questions

Is JPG to PDF lossless?

Yes, in the sense that the JPEG is not re-compressed. Its data is copied into the PDF unchanged, so the photo is exactly as it was. A photo over the device's pixel limit is the exception: it is scaled down and re-saved at quality 90.

Is PNG to PDF lossless?

Yes. The pixels are kept exactly and stored with lossless compression. No JPEG step is involved, even when a PNG over the pixel limit is scaled down first.

Why did my PDF get bigger than the images?

Lossless pages keep all the image data. PNG data is compressed again for the PDF, which can make it a little larger or smaller than the PNG files.

Can Deckle make a blurry image sharper?

No. The PDF keeps the image as it is. Use the highest-resolution original you have.

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