PhotoRiyaHow to convert an image to grayscale
Drop your image onto the box above. It is converted to grayscale at once. Keep the Natural filter for a faithful conversion, or pick another colour filter if some colours should come out lighter or darker. Choose a format and press Download.
The tool reads JPG, PNG, WebP, GIF, BMP, TIFF and other formats, so it also works as a quick way to change format at the same time.
How the grayscale conversion works
Each pixel's red, green and blue values are mixed into a single gray. The Natural filter uses the standard Rec. 709 weights, about 21% red, 72% green and 7% blue, because the eye is far more sensitive to green than to blue. The mix is done in linear light and converted back to the sRGB curve, so the brightness of the gray matches the brightness of the colour.
The result has equal red, green and blue values in every pixel. With PNG the file stays sharp, and with JPG it is smaller.
When to use grayscale
Grayscale images are useful for printing in black and ink, for documents that will be photocopied, for reducing file size, and for preparing images for OCR or machine learning. For an artistic result, use the black and white converter with colour filters and film grain.
Questions people ask
How do I convert an image to grayscale?
Drop your image onto the tool above. It's converted to grayscale at once. Choose a format and press Download.
Which formats can I convert?
JPG, PNG, WebP, GIF, BMP, TIFF and several others. You can save the result as PNG, JPG or WebP.
Will the grayscale image be smaller?
Often, yes, especially as JPG, but not always. The colour data is gone, but the file size also depends on the detail in the picture.
Does it keep transparency?
Transparent areas are flattened onto a white background for JPG. PNG and WebP also get a solid background, because this tool processes the whole picture as one.
Is my photo uploaded to a server?
No. The conversion runs inside your browser tab, on your own device, and nothing is sent anywhere. That also makes it instant: there's no upload or queue.
What size is the result?
Photos are kept at their full size up to 4,096 pixels on the long side. Larger photos are reduced to that, which is still more than enough for screens and A4 prints.
Is it free?
Yes. There is no limit, no watermark and no account. PhotoRiya is open source under the MIT and Apache 2.0 licenses.
More free tools
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