Create Black and White Image

Strictly, black and white means only two values: pure black (0) and pure white (255). Grayscale means a continuous spectrum of gray. Most photo apps call grayscale “B&W” because that’s the colloquial term – but technically a grayscale photo has thousands of gray levels, not just two. This tool offers both, labelled correctly.

For each pixel, compute its luminance. If it’s above the threshold, output white; otherwise black. Result: a pure 1-bit image with no gray levels at all. Looks harsh on photos but is correct for documents, line art, and any “stamp” effect.

Error-diffusion algorithm from 1976. When a pixel becomes black or white, the “error” (how much it was rounded) gets distributed to neighbouring pixels. The result is a 1-bit image that visually approximates the original’s gray levels via tiny patterns. Common in old newspapers and laser printer output.

Ordered dithering using a fixed pattern matrix (this tool uses 4×4). Faster than Floyd-Steinberg and gives a characteristic crosshatch/grid look – instantly recognisable from old video games (Game Boy graphics, Mac System 1/2 era). Pixel-perfect deterministic for the same input.

For modern digital photos: Rec 709 (matches sRGB primaries). For legacy SDR / NTSC content: Rec 601 (default – it’s the historical standard and what most older tools used). Simple average is for non-photographic content (diagrams, screenshots) where perceptual accuracy doesn’t matter.

JPEG is bad at high-contrast 1-bit content – its DCT compression introduces “ringing” artefacts around sharp edges. For true B&W output, prefer PNG (lossless, perfectly preserves the binary pixels). JPEG is fine for grayscale.

Yes. The alpha channel is preserved through grayscale and threshold modes. Dither modes also preserve alpha. Transparent pixels stay transparent.

10 MB. Larger images work in principle but the main-thread canvas processing gets slow.

No. All image processing happens through the Canvas API inside your browser – nothing is sent to a server, logged, or stored, and the tool keeps working offline once the page has loaded.

Not in this tool. For batch B&W conversion, a desktop image editor (ImageMagick, Photoshop actions) is more efficient.