How to make a picture black and white
- Choose a photo, or several at once.
- Pick a look: Grayscale, Black & white only (line art) or Dots (a dithered, newspaper-like look).
- Choose a grey method and adjust brightness and contrast. For line art, press Auto threshold or move the slider.
- Download the photo, or all of them as a ZIP.
Grey methods compared
Every method turns a colour into one grey from 0 (black) to 255 (white), but they weigh red, green and blue differently. Here is the same red (229, 57, 53) and blue (30, 136, 229), worked out by the tool:
| Method | Red becomes | Blue becomes |
|---|---|---|
| Natural | 93 | 120 |
| Classic | 108 | 115 |
| Average | 113 | 132 |
| Lightness | 141 | 130 |
| Red filter | 229 | 30 |
| Green filter | 57 | 136 |
| Blue filter | 53 | 229 |
With Natural the red comes out darker than the blue (93 against 120), as it looks to the eye. With the Red filter the red turns almost white (229) and the blue nearly black (30), which is why a red filter darkens blue skies. Natural uses the same weights as the B&W preset in Photo filters.
Pure black and white: threshold and dithering
With Black & white only, every grey at or above the threshold becomes white and everything darker becomes black. Auto threshold uses Otsu's method: it tries every cut and keeps the one that best separates the dark group of greys from the light group, which suits scans of drawings, handwriting and signatures. Dots spreads the leftover grey to the neighbouring pixels (Floyd–Steinberg dithering), so shading survives as a pattern of black and white dots.
For a signature with a transparent background, make it black and white here, then press Convert under Next step: the image converter opens with your picture, where PNG with Make a colour transparent: White removes the paper.