Images to PDF

How it works

Each image is read in the browser and placed on a page that is one point per pixel of your chosen paper size: A4 is 595.28 × 841.89 points and US Letter is 612 × 792, which is the scale every PDF viewer uses. With a fixed page size the picture is scaled down until it fits inside a 24-point margin on all sides, centred on the page, and it is never scaled up past its own size. With the matching-page option the page is cut to the image's own pixel dimensions, so nothing is scaled at all. JPEG and PNG files are copied into the PDF exactly as they are — no second round of compression — while any other format is decoded and re-encoded as PNG, because that is what a PDF can carry. One unreadable file is skipped and named in the result instead of stopping the whole job.

Worked example

A 1600 × 1200 photo on A4: the margins leave 595.28 − 48 = 547.28 points across and 841.89 − 48 = 793.89 points down, so the scale is the smaller of 547.28 ÷ 1600 = 0.342 and 793.89 ÷ 1200 = 0.662, which is 0.342. The picture is drawn at 1600 × 0.342 = 547.28 points wide and 1200 × 0.342 = 410.46 points tall, centred on the sheet. Three images give a three-page PDF, and each JPEG keeps its original bytes.

Questions and answers