Threshold Image Filter
Every pixel goes pure black or pure white: drag the slider to pick where the line falls.
or browse filesdrop an image here or paste
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Every pixel goes pure black or pure white: drag the slider to pick where the line falls.
or browse filesdrop an image here or paste
A threshold filter makes one decision about every pixel: is it brighter than the level you set, or darker? Brighter goes pure white, darker goes pure black, and nothing survives in between. There are no greys in the result at all, which is what separates thresholding from an ordinary black and white conversion. Drag the slider and the preview follows, so you can watch text detach from a grey page or a face collapse into a stencil and stop exactly where it looks right.
People look for this as a threshold generator, a threshold maker or a threshold editor; they are the same one-slider operation, and it runs on photos, scans and screenshots alike. The level runs from 0 to 255 and starts at 128, the middle. Lower it and only the darkest parts stay black; raise it and more of the picture falls to black. On a scan of a document the useful range is usually narrow, so move in small steps.
Drop a photo or a scan onto the page, or paste one from the clipboard, then drag the slider until the result reads the way you want. Download as PNG, which is the right format for flat black and white images and keeps the file small, or as JPG or WebP if something downstream needs them. Everything runs in your browser: the image is never uploaded, there is no signup, and no watermark is added.
Scanned documents and phone photos of paper are the most common reason to binarize an image. Uneven lighting leaves the page grey and the text muddy; a threshold throws the page away and keeps the ink, which is what OCR software wants to see and what makes a scan print cleanly.
Beyond documents, a binary image is the input that cutting and printing machines expect. Stencils, screen-printing separations, vinyl cutters, laser engravers and embroidery digitisers all need a shape that is either on or off, not a gradient. The same conversion is a strong graphic effect in its own right for posters, stickers and high-contrast portraits.
There is no correct number, only the one that suits your image. For dark text on white paper, start at the middle and drop until the letters are solid but the background has not begun to speckle. For a portrait, higher levels keep more shadow and read as a woodcut; lower levels leave only the darkest features and read as a stencil.
If the photo is lit unevenly, no single level will work everywhere at once - one side of the page will fill in before the other clears. Fixing the lighting first helps: raise the contrast or the brightness before thresholding, and the level that works becomes much easier to find.
They are different conversions and it is worth knowing which you want. A black and white converter keeps the full range of greys, so the photograph still looks like a photograph. A threshold keeps two values only. If your result looks harsh and you wanted a normal monochrome photo, the converter is the tool; if it looks too soft and you wanted flat shapes, you are in the right place.
The preview and the download apply the same cut to the pixels, so what you see is what you save, at the full resolution of the file you loaded. Transparency is kept: a PNG with a transparent background comes back thresholded with the background still transparent, rather than gaining a black one. All of it happens on your device through the canvas API, so no image is transmitted anywhere and the page keeps working offline once it has loaded.
Open the picture here and drag the slider. Every pixel brighter than the level becomes white and every darker pixel becomes black, and the preview updates as you drag. Download it as PNG, JPG or WebP at the original resolution. No account or upload is involved.
That is what this page does - binarization and thresholding are the same operation. Load the image, pick the level, and the result contains only two values, 0 and 255, with no greys between them.
A black and white conversion keeps every shade of grey, so a photo still looks like a photo. A threshold allows only pure black and pure white, so the result is flat shapes. Use the threshold when something downstream needs an on-or-off image, such as OCR, a stencil or a cutting machine.
It depends on the image, which is why this is a slider rather than a button. Dark text on white paper usually lands somewhere below the middle; portraits often want a higher level to keep some shadow. Move in small steps and watch the point where the background starts to speckle - that is one step too far.
Because the page was lit unevenly, so one area is genuinely darker than another and a single level cannot suit both. Even out the lighting first with the contrast or brightness tools, then threshold the result.
No. The picture is decoded, thresholded and encoded in your browser, at preview and at full download resolution alike. Nothing is sent to any server, and the tool keeps working with the network disconnected once the page is open.