Signature resizer

How to sign for an upload

1. Plain white, unruled paper. Printed lines, squares and letterheads end up in the upload. A blank sheet or the back of a form works.
2. Black or blue pen, pressed normally. Ballpoint and gel pens both photograph well. Pencil, light-coloured ink and thin fine-liners fade at 140 × 60 pixels; the tool can strengthen faint strokes but cannot invent missing ones.
3. Daylight or a lamp from the side. Stand so that your own shadow and the phone’s shadow do not fall on the paper. A shadow across the sheet is evened out automatically; a shadow that covers the strokes is not.
4. Fill the frame, hold the phone flat. Get close enough that the signature is a good part of the photo, with the phone parallel to the paper so the strokes are not skewed. The photo does not need to be cropped by hand: the blank paper around the signature is trimmed here.
5. Sign as you normally sign. Many forms reject a signature written in capital letters or only initials, because it will be compared with the one on your documents later.

Why signatures get rejected

• Too small in the box. A signature that occupies a corner of a wide photo becomes a speck at 140 × 60 pixels. Trimming fixes this; the result also warns when the strokes fill too little of the frame.
• Grey or yellow paper. A phone photo of white paper is rarely white. Portals and reviewers expect a clean background, which is what the cleanup produces.
• Cut edges. Cropping a wide signature to a fixed shape by hand often slices a flourish. With cleanup on, an exact size is reached by adding paper around the signature, never by cutting it.
• Wrong pixels or KB. The form’s numbers are rules, not suggestions. Set them here and the result is checked against them under both KB readings before you download.
• Wrong file type. A PNG with a transparent background is turned into a JPG on white; HEIC from an iPhone is converted when the browser can read it.
• Capitals, initials or a different signature. No tool can check this, which is why the result asks you to confirm it before uploading.

What 140 × 60 px means

140 × 60 pixels is a small, wide box: 140 pixels across and 60 down, a shape of 7 to 3. It is a pixel count, not a size on paper, so a 6 cm wide signature and a 2 cm wide one both end up 140 pixels across. Most signatures are wider than 7 to 3 already; a short signature is placed in the middle of the box with white paper on both sides, so nothing is stretched. The same applies to 250 × 80, 300 × 100 and any custom size: the signature is fitted into the shape, then the whole box is scaled to the exact pixel count.

KB rules bite in an unexpected direction here. A clean signature is mostly white and compresses extremely well, so 140 × 60 pixels can come out at 3 or 4 KB even at the highest JPG quality. When a portal asks for a minimum such as 10 KB, SizePrep raises the quality first, then keeps more of the real paper texture from your photo, and only reports a problem when the minimum still cannot be reached. It never pads a file with junk bytes, because some portals re-encode uploads and a padded file can fail there.

What cleanup does, and does not do

Cleanup estimates the brightness of the paper across the photo, divides every pixel by the paper under it (which removes shadows, uneven light and the colour cast of the lighting), stretches faint ink towards black by the same factor in every colour channel (so blue ink stays blue and black stays black), and trims to the strokes with a small margin. Dust, the table under the paper and printed ruled lines are ignored when the trim is chosen. It never redraws, smooths or thickens a stroke: use the Before / After toggle and the zoom to check that the result is still your signature, and switch cleanup off for a plain resize with a movable crop.

Known limits, in case the result looks wrong:

• Ruled or squared paper inside the kept area stays visible, and a dark line crossing the signature can widen the trim.
• Dark objects touching the signature (a pen, a finger, the edge of a card) count as ink and widen the trim.
• Glare that burns out part of a stroke cannot be recovered; retake the photo without the reflection.
• Coloured or patterned paper is treated as the paper colour and neutralised; strong patterns confuse the trim.
• Pencil and very faint ink below the threshold are treated as paper.
• A signature touching the photo edge has no paper to keep as margin, so white is added instead.
• Photographs of people are never cleaned: the cleanup switches itself off when the image does not look like ink on paper.

For a signature that needs an exact pixel size together with other rules, the pixels and KB resizer gives the same engine without cleanup, and the image size checker reads the numbers of a file you already have.