How to adjust string art parameters

Prepare the photo

Use a JPG, PNG, WebP, or GIF with a clear dark subject on a light background. The working picture is turned into darkness: in the small circle labelled "What the algorithm sees", darker areas are where more thread will go. If that circle shows a grey blob, fix the crop and contrast before you generate. Generating first and hoping the sliders catch up wastes a long run.

There is a generated sample if you want to learn the controls without a photo. It is an original drawing made in the page, not a picture of a real person.

• Crop to circle is on by default. The photo fills the circle and anything outside is cut. Turn it off to fit the whole photo inside the circle, which leaves blank corners and a smaller subject.
• Zoom runs from 1.0x to 3.0x. Use it to push a face or a logo larger. Past about 2x you are cropping hard, so check that the subject is still inside the circle.
• Shift X and Shift Y run from -50 to 50. They move the photo across the circle. Centre the part you care about; the thread cannot draw anything that falls outside the circle.

A busy background becomes a ring of stray lines. Crop tighter, or raise contrast so the background goes light in the "what the algorithm sees" preview, before you add pins.

Contrast and auto levels

Contrast runs from 0.5 to 2.2, and the page starts at 1.1. Higher contrast pushes darks darker and lights lighter in the darkness map. Lower contrast flattens the photo, so the search has less reason to prefer the subject over the background.

Auto levels is on by default. It stretches the tones inside the circle between the 2nd and 98th percentile, which helps a flat or foggy photo. Turn it off when the photo is already high contrast and the stretch blows the subject out to solid black. Look at the small circle after each change. That view, not the original colour photo, is the input to the line search.

Number of pins

The choices are 150, 200, 300, 360, and 400. 300 is the default. The Quick, Balanced, Detailed, and Ultra presets set pins, max lines, and line strength together; Fine-tune changes them one by one. 360 and 400 pins preview for free, and their printable templates come with the Pro Pack. Pin 0 is at 12 o'clock and numbers go clockwise. More pins give the search more places to end a line, and they also mean more nails to hammer and a longer sequence. Fewer pins are quicker to build and look coarser.

The page shows pin spacing from the diameter you enter: the circumference divided by the pin count. At the default 40 cm circle, 300 pins are closer together than 150 pins. If the spacing is smaller than the nails you own, pick fewer pins or a larger circle. The sequence is computed again when you change the pin count, so generate a preview for 150 and for 300 and compare them on screen before you buy nails.

Max lines

Max lines is the cap on steps. The field accepts 200 to 6,000, in steps of 100, and starts at 3,000. One step is one segment from the current pin to the next.

The search can stop before the cap. It stops when another line would not improve the picture. The status line then says it stopped because extra lines no longer improve the match. It also stops when it hits the cap. A low cap, around a few hundred, is a fast way to see whether the crop is right. A cap of 3,000 to 6,000 is for a denser portrait, and it takes longer to compute and longer to thread.

If the preview looks finished but the step count is far below the cap, raising max lines will not add much. Change the photo, contrast, pin count, or line strength instead, then generate again.

Line strength

Line strength is the slider from 10 to 50. The default is 18. There is no separate line-weight or opacity control. This one number is how much darkness each new line is assumed to remove when the search picks the next pin.

A higher strength fills dark areas in fewer steps, and the result usually looks heavier. A lower strength keeps looking for lighter lines, so the sequence is often longer and finer, until it hits max lines or stops because more lines do not help. The on-screen preview uses the same strength to set how opaque each stroke looks. The stroke width on that preview stays about one pixel at the working resolution; do not expect the slider to draw a thicker nail-to-nail cord by itself.

If a face turns into a solid black disc, lower the strength or the contrast and generate again. If the portrait is only a faint outline and the step count already hit the cap, raise the strength a little or allow more lines. Compare two previews. The tool does not store a "best" strength for a given photo.

Board diameter, thread, and nails

Actual board diameter is the circle through the pins, in centimetres, from 10 to 100. The default is 40. It is not the outer size of the wood. Measure across the pin circle.

Changing the diameter does not invent a new pin sequence. The lines are planned on a fixed circle in the browser. The diameter scales three things: the pin spacing shown on the page, the estimated thread length, and the 1:1 template in the full pack. You can change the diameter after a preview. The length on the page updates immediately, and the template uses the current diameter when you download. Generate again only when you change the photo, the pin count, max lines, or line strength.

Under Calibrate thread estimate:

• Thread diameter, 0.05 mm to 3 mm, default 0.5 mm.
• Nail or pin diameter, 0.3 mm to 6 mm, default 2 mm.

The estimate adds the straight chord lengths, scaled to your board, plus a wrap allowance per step of pi/2 times (nail diameter + thread diameter). That allowance is an assumption, not a measurement from a physical board. Other planners can show a different total. These two fields do not change which pins are chosen. They only change the length number and the note on the PDF, including if you edit them after the preview.

Generate, stop, and export

Generate preview runs in a worker in your browser and draws lines as they are found. Stop ends the search early; the sequence you have so far is what the export uses. The stats row shows the step count, the thread estimate, the pin spacing, and the compute time.

First steps preview saves the opening part of the sequence as a PDF or a text file. The count field runs from 10 to 1,000 and starts at 100. That is enough to start a board and see whether the crop was right, without threading thousands of steps.

The full pack is free as well. It contains:

• A 1:1 pin template tiled onto A4 sheets, with a 10 mm overlap, alignment crosses, and a 50 mm scale bar on each page.
• A step table with a tick box for every 10 steps. The sequence starts at pin 0.
• The complete pin sequence as a .txt file.

Print the PDF at 100 percent, not "fit to page", and check the 50 mm bar with a ruler before you nail anything. Join the pages, fix them to the board, and put a nail on each pin dot. A paid Pro Pack (print-shop poster or Letter/A4 tiles, large-print booklet, session planner, 360 and 400 pins) is planned; until checkout opens, its button only records that you are interested.

Stringing mode, on the planner page, shows one pin at a time in large type with a map of the board, can read the numbers aloud, and remembers your place on this device. It is free for 150 to 300 pins.

A practical order

1. Load the photo or the sample. Crop, zoom, and shift until the subject fills the circle.
2. Set contrast and auto levels until the small preview has a dark subject and a light ground.
3. Pick 150 pins and a few hundred max lines for a quick look. If the shape is right, move to 200 or 300 pins and a higher line cap.
4. Nudge line strength if the preview is a solid blot or a faint sketch.
5. Enter the real pin-circle diameter and your thread and nail diameters, then download the full pack. Those three numbers do not require a new preview.

Frequently asked questions

How many pins should I use?

The planner offers 150, 200, 300, 360, and 400 pins, and 300 is the default. 360 and 400 pins preview free; their templates are part of the Pro Pack. More pins can follow the photo more closely and take more nails. Fewer pins are faster to build and look coarser. Generate a preview at two settings and compare them. Pin 0 is at 12 o'clock and the numbers run clockwise.

What do max lines and line strength do?

Max lines caps the steps, from 200 to 6,000, starting at 3,000. The search can stop earlier when more lines would not improve the picture. Line strength, from 10 to 50 with a default of 18, is how much darkness each line is assumed to remove. Higher strength fills in faster and looks heavier. There is no separate opacity or line-width slider. The preview uses this same strength for stroke opacity, and the stroke width stays about the same.

How should I set contrast and auto levels?

Contrast runs from 0.5 to 2.2 and starts at 1.1. Auto levels, on by default, stretches the tones inside the circle. Watch the small circle that shows what the algorithm sees: darker means more thread. Turn auto levels off if it crushes a photo that was already high contrast. Crop, zoom (1 to 3), and shift (-50 to 50) before you rely on contrast alone.

Does the board diameter change the pattern?

The diameter, 10 to 100 cm, is the circle through the pins, not the outer board. It scales pin spacing, the thread estimate, and the 1:1 template. It does not pick different pins, so you do not need another preview just to update the template. Thread diameter (0.05 to 3 mm, default 0.5) and nail diameter (0.3 to 6 mm, default 2) affect only the length estimate. Enter the real sizes before you download.

How do I print and use the template?

Download the full pack and print it at 100 percent, not fit to page. The template is split across A4 pages with a 10 mm overlap, alignment crosses, and a 50 mm scale bar. Check that bar with a ruler. The step table has a tick box every 10 steps, and the sequence starts at pin 0. A shorter first-steps PDF or text file, 10 to 1,000 steps, is there if you only want to start the board.

Why does the thread length disagree with another planner?

The number is an estimate: chord lengths scaled to your diameter, plus a wrap allowance of pi/2 times (nail diameter + thread diameter) per step. That allowance has not been measured on a physical board. Buy extra thread. The planner is an early version for a round board and a single thread colour.