Scan to PDF

Taking usable photos

Lay the page flat on a contrasting surface, fill the frame, and keep the camera parallel to the paper as far as possible. Shadows and a slight angle are fine: the corner tool and the Document filter deal with them. Avoid cutting off a corner, because the straightening needs all four. On a phone, Use the camera opens the rear camera; on a laptop it opens the webcam, which works for a page held up to the screen but a phone photo dropped in will be sharper.

• One photo per page; capture several in a row and press Done
• Keep all four corners of the paper inside the frame
• Daylight or a desk lamp from the side beats a flash, which blows out the centre

Straightening by the corners

Open Corners on a page and drag the four handles onto the corners of the paper; arrow keys nudge a handle by four pixels, Shift and arrow by twenty. The quadrilateral is mapped onto a rectangle whose width and height are the average of the opposite edges, so a page photographed at an angle comes out with straight edges and the right proportions. Whole photo resets the handles. Corners are not detected automatically yet; the thumbnails update as soon as you set them.

The clean-up filters

Document estimates the brightness of the paper under every pixel from the brightest parts of each neighbourhood, divides by it, and stretches the result so paper becomes white and ink stays black. It removes the grey cast, shadows across the page and the gradient from a lamp on one side. Black & white thresholds that result and stores the page losslessly, which gives the smallest file for forms and typed text. Grayscale keeps shading for pencil and photos; Colour keeps stamps, highlighter and signatures in ink colour.

Page size and resolution

Photos are scaled to at most 2200 pixels on the long side, about 250 dpi for A4, which keeps a ten-page scan around two to four megabytes with the Document filter, and well under that in Black & white, which is stored losslessly. A4 and US Letter fit the straightened page on standard paper, portrait or landscape following the photo. Photo size makes the page the shape of the picture at 200 dpi, which suits receipts, cards and odd formats.

Order, rotation and removal

Pages appear in the order they were captured or dropped. The arrows move a page up or down, the rotate button turns it by 90 degrees, and the cross removes it. HEIC photos from an iPhone are decoded in the browser, and EXIF orientation is applied before anything else, so a photo taken upright stays upright.

After scanning

The download is paperkit-scan.pdf with one page per photo and the image embedded as JPEG. It has no text layer, so it is not searchable; that needs OCR, which PaperKit does not do yet. Compress PDF can shrink it further, Merge PDF appends it to an existing document, and Protect PDF adds a password if the scan is confidential.