Image to Black & White Converter

No. The entire process — reading the file, pixel conversion, dithering, through download — runs 100% in your device’s browser using JavaScript and <canvas>. Images never leave your device, no server receives files, and this tool keeps working offline after the page loads.

Grayscale turns each pixel into one light-dark value (0–255) so photos look black-and-white with gradation. Threshold forces each pixel to PURE black or PURE white by a threshold (e.g. 128): good for text/photocopy but destroys gradation detail. Dithering also produces pure 1-bit black-and-white, but spreads quantization error to neighboring pixels so the eye sees an illusion of gradation — much smoother results for photos.

You can choose three luminance formulas. BT.709 (default, HDTV standard): 0.2126×R + 0.7152×G + 0.0722×B. BT.601 (analog TV standard): 0.299×R + 0.587×G + 0.114×B. Or simple average (R+G+B)/3. Example: a pure red pixel (255,0,0) becomes 54.21 with BT.709 and 76.24 with BT.601 — because human eyes are most sensitive to green, green gets the largest weight.

Each pixel is rounded to black (0) or white (255) by threshold, then the difference (error) is spread to unprocessed pixels: 7/16 to the right, 3/16 to the lower-left, 5/16 below, and 1/16 to the lower-right. Accumulated error makes dark areas produce denser black dots — exactly the technique printers and newspapers use to print photos with black ink only.

Use pure threshold for documents, text, stamps, logos, or photocopy effects — the subject is truly only two colors. Use dithering (Floyd–Steinberg for photos, Bayer for print texture) for portraits, landscapes, or gradated images that must stay readable in 1-bit, e.g. for screen printing, e-ink, or thermal printers.

Photocopy: threshold 128 with +30 contrast for sharp text. Newspaper: Floyd–Steinberg dithering at threshold 128 with +15 contrast, mimicking newsprint. Stamp: threshold 160 with +40 contrast for thick black stamp blocks. Sketch: 8×8 Bayer ordered dithering at threshold 140 giving pencil-sketch-like hatching texture. All presets can be tweaked manually after selection.

PNG (lossless, best for 1-bit results because of small size) or JPEG at 92% quality. Output size can be 100%, 75%, 50%, or 25% of the original — useful for lighter web files. Filenames automatically follow the original with a -bw suffix.

Yes. Batch mode accepts up to 30 images, applies the same settings to all, then packs results into one downloadable ZIP file. Everything is still processed locally in the browser — no server queue.

100% free, no watermark, no account signup, no conversion limits. This tool is a single static HTML file with no server, so there are no operating costs to cover with a paywall.

image-file-size is an ESTIMATOR: it computes estimated file size from dimensions and bit-depth without changing the image. This tool is an EDITOR: it actually turns your image pixels black-and-white and produces a new downloadable file. They complement each other — convert here first, then check the size estimate there.