Convert TIFF to SVG

TIFF is one of the few image formats that holds more than one image, and document scanners use that constantly: a drawing set, a fax, a batch of survey sheets and an archive record all commonly arrive as a single TIFF with several pages inside it. The reader here takes the first one and stops.

There is no warning attached to that, so it is stated here instead. The other pages are still in your file — nothing is damaged — but the SVG you download contains sheet one and nothing else. Split the TIFF in the scanner software, in IrfanView or in ImageMagick before converting, and trace each sheet separately. This is the first thing to check on this page, because a drawing set that traces "successfully" and silently loses three sheets is a much worse outcome than one that fails.

On a clean logo, sharp detail preserves the crispness that was the point. On a scan it does the opposite, because a scan is not clean: it carries dust, paper grain, halftone dots from an original that was printed, and the ragged edge that any physical line has once it has been through a sensor.

Measured on a 1,200 by 900 line drawing with ordinary scanner speckle, taken through this site’s own TIFF writer and reader first: smooth at four colours produced 33,221 bytes in 63 paths. Sharp at eight colours produced 903,740 bytes in 3,810 paths — twenty-seven times the file for the same drawing, and roughly three and a half thousand of those paths are dust. Smooth discards any shape below sixteen pixels, which is exactly the size range that speckle occupies, and that single setting does more for a scan than everything else on this page combined.

This is the point that decides whether the file is useful downstream, and it surprises people who have used a raster-to-vector product built for CAD. Tracing finds regions of similar colour and draws a closed path around each region. A drawn line is a long thin black region, so what comes back is a loop running down one side of the stroke and back up the other.

For anything visual — a print, a large display, a redraw reference, a screen-printed pattern — that is exactly right, because the result looks like the drawing and scales without going soft. For a machine it is not. A plotter or an engraver following the path traces the outline of every line rather than the line itself, and a CAD package importing it gets two edges where the draughtsman drew one, with no dimensions, no layers and no arcs. Centreline extraction is a different algorithm and is not what runs here. Treat the SVG as an accurate background to draw over.

TIFF is less a format than a filing system for images, and readers disagree about it more than about anything else on this site. The one used here is utif2, and it was checked against files rather than against the specification: uncompressed, LZW, Deflate, PackBits, JPEG-in-TIFF and Group 3 and Group 4 fax all decode, in colour, in greyscale and in one-bit black and white.

Two limits are worth knowing before you scan. Sixteen bits per channel are read but reduced to eight by keeping the high byte, which is irrelevant for a line drawing and would matter for a photographic plate. And a CMYK TIFF — what a print workflow produces — is converted to screen colour by formula rather than through the profile embedded in the file, so the colours shift. For a black-on-white drawing neither changes anything you will notice; both are stated because the same reader serves the photographic pages in this family.

A line drawing has two colours: ink and paper. Four gives the quantiser room for ink, paper and the two intermediate greys that anti-aliasing and scanner blur put along every edge, and that is the right choice for almost everything this page is used for. The control starts at eight, which is the sensible default for a flat illustration and one step too generous for a scan, so move it down before you convert.

Going higher does not recover detail from a scan; it recovers noise. Sixteen and thirty-two colours give the quantiser enough palette entries to treat each shade of grey paper and each halftone dot as a region worth outlining, and the shape count climbs accordingly. The exception is a scan of something genuinely coloured — a hand-drawn map, an annotated plan with red and blue markup, a stained pattern sheet. There, eight is a sensible start, and it is worth deciding in advance which colours you actually need rather than asking for all of them.

The tracer has no idea what paper is. A scan with a warm grey background and grey-black lines gives it a picture in which the "flat regions" include large areas of nearly-but-not-quite-uniform paper, and it will dutifully outline the boundaries between them.

Ten minutes in any image editor is worth more than every option on this page. Push the levels until the paper is genuinely white and the ink is genuinely black, crop away the scanner bed and the page edges, straighten the sheet, and remove the punch holes and the staple shadow. If the scanner offers a bitonal or "document" mode, using it is the same fix applied at capture time — and a one-bit TIFF traces cleanly because the decision the tracer would have had to guess at has already been made properly.

Anything longer than 1,600 pixels on its longest edge is scaled down first. This bites harder here than on any other source on the site: a 300-dpi A4 scan is already about 2,480 by 3,510 pixels, and a 600-dpi one about 4,960 by 7,020, so nearly every scan that arrives is reduced.

It costs less than it looks. The SVG is resolution-independent, so a drawing traced at 1,600 pixels and the same drawing traced at 7,000 pixels render identically at any size; what changes is how tightly the outlines hug the original grid, and on a scan the tighter fit is mostly hugging speckle. The practical consequence is that scanning at 1,200 dpi for this purpose is wasted time and disk. Scan at 300 to 400 dpi bitonal, get the levels right, and you have handed the tracer everything it can use. The one case for a higher-resolution scan is a very large sheet where fine hatching would otherwise merge into solid grey at 1,600 pixels — there, crop and trace in sections.

Open it in Inkscape and look at the shape count first: the status bar tells you immediately whether the trace worked. Sixty shapes for a drawing is a good result and a few thousand means the speckle won, in which case go back and re-scan or re-level rather than trying to clean it up.

Then delete the full-canvas background path, select by colour and remove the grey intermediates if you only want ink, and use Edit → Find or a rubber-band selection to sweep up the remaining specks. For a cutter, check that each region you intend to cut is one closed path rather than several — the trace has no concept of a design, only of areas — and set the stroke to none so the machine follows fills rather than the one-pixel outline stroke the tracer writes on every path.

If the scan is a document rather than a drawing — a contract, a records request, a set of forms — tracing is the wrong tool entirely. TIFF to PDF keeps every page and produces the file the recipient is expecting, and TIFF to TXT reads the words with Tesseract if what you needed was the text.

If the scan is a photograph or a print plate, no tracer will help: TIFF to PNG keeps every pixel exactly, and TIFF to JPG or TIFF to WebP makes it small enough to send or publish. Tracing is worth doing when the scan is genuinely line work and genuinely has to become shapes, which is a narrower case than the file extension suggests.

The TIFF is decoded by utif2, scaled, traced and written out entirely in the tab. Nothing is uploaded and there is no account or daily allowance, which is the point on a page whose typical file is a client’s drawing, a patent figure or a survey nobody is authorised to post to a third party.

The tracer is imagetracerjs: 46 KB of pure JavaScript under the Unlicense. It is not the best available. potrace and autotrace fit cleaner curves and are GPL; VTracer is stronger again and properly licensed, but its only browser packaging declares no licence at all, which this project treats as blocked rather than permissive. For a scan the choice matters less than it would elsewhere, because on this input the quality of the scan dominates the quality of the tracer by a wide margin.