Convert BMP to JPG

A BMP photo is heavy: a 12-megapixel picture stored as a bitmap is around 36 MB, because the format keeps three bytes for every pixel and does not compress them. Email providers cap attachments at 20 or 25 MB, and most web forms take a few megabytes at most. As a JPG at quality 90 the same picture is usually 3 to 5 MB and looks the same on screen.

Choose JPG when the bitmap is a photograph or a scan of a photo: old digital cameras, webcam captures, frames grabbed by capture cards and security software often write BMP. For screenshots, line art and anything with sharp text, JPG blurs edges slightly; the BMP to PNG page keeps those pixel-perfect and still cuts the size a lot.

Everything happens inside this tab. The browser decodes the bitmap, the JPG encoder runs at the quality you set, and each file downloads directly from memory.

Where do BMP photos still come from? Film and flatbed scanner software set to "bitmap" output, dental and veterinary x-ray viewers exporting a frame, older point-and-shoot cameras in their uncompressed mode, and screen grabs from video capture cards. Many of those programs never ask about format, so a whole folder of multi-megabyte BMPs piles up before anyone notices.

Converting a batch is the usual case: drop the whole folder, keep quality at 90, and download a zip of JPGs a tenth of the size. The JPGs keep the pixel dimensions of the originals. BMP files carry no camera metadata to begin with, so there is nothing about where or when the picture was taken to preserve or to leak.

Transparency is rarely an issue with BMP, since nearly every bitmap is 24-bit with a solid background. The occasional 32-bit bitmap with an alpha channel, typically an icon or a graphic exported from a design tool, has its see-through areas filled with the background colour from the options, white unless you change it. For that kind of image, a PNG keeps the transparency and will look better.

On Windows, Paint and the Photos app can also save a BMP as JPG one file at a time through Save as. That works for a single picture. For dozens of bitmaps, or on a computer where you cannot install anything, doing the whole batch here is quicker, and the quality setting is under your control rather than fixed by the app.