BMP to JPG Converter

Encoding: the BMP uses usually none; RLE for some 4 and 8-bit files; JPG uses lossy DCT coding in 8×8 pixel blocks, with colour usually stored at half resolution, and the download is a standard JPEG at the quality you choose.

Bit depth: 1, 4, 8, 16, 24 or 32 bits per pixel in the BMP; JPG allows 8 bits per channel, and the JPG written here has 8 bits per channel.

Colour: RGB or an indexed palette in the BMP; JPG supports YCbCr shown as RGB, greyscale, or CMYK from print software, written here as 8-bit sRGB.

Transparency: the BMP stores it as an optional fourth byte in 32-bit files, which many programs ignore; the JPG has none, so transparent areas are filled with the colour you choose.

Metadata: the BMP can carry nothing beyond the header's resolution fields (and a colour profile in rare V5 headers); JPG can carry EXIF (camera, date, GPS), XMP, IPTC and an ICC profile in APP segments, but nothing is copied across.

BMP stores raw, uncompressed pixels. Files are huge but trivially simple, which is why some legacy Windows software, embedded displays and printers still ask for it.

A BMP is a 14-byte file header ('BM' and the offset to the pixels), a DIB header (40 bytes, or 108 and 124 bytes in the V4 and V5 versions that add colour masks and alpha), an optional palette, then pixel rows padded to 4 bytes and normally stored bottom-up.

BMP files usually come from Windows Paint, legacy Windows programs, embedded displays and some scanners.

JPEG is the universal photo format. It compresses by discarding fine detail the eye is least sensitive to, which makes photos small but blurs sharp edges and text if pushed too far.

A JPEG starts with the bytes FF D8 and is a run of marker segments: APP1 carries EXIF and often a thumbnail, APP2 an ICC profile, DQT the quantization tables that decide the quality, and SOS the compressed scan, which ends at FF D9.

JPG is the better choice for photographs that need to open anywhere, while BMP suits legacy software and embedded systems that require it.

JPG strengths: Opens everywhere: every browser, phone, camera, printer and app; Small files for photographs; Adjustable quality from tiny to near-lossless. Drawbacks to weigh: No transparency; Lossy: every re-save loses a little more; Blocky artifacts around text, logos and sharp lines.