PNG to BMP Converter

Encoding: the PNG uses lossless DEFLATE with a prediction filter chosen per row; BMP uses usually none; RLE for some 4 and 8-bit files, and the download is an uncompressed 24-bit BMP, or 32-bit with alpha when the image has transparency.

Bit depth: 1, 2, 4, 8 or 16 bits per channel in the PNG; BMP allows 1, 4, 8, 16, 24 or 32 bits per pixel, and the BMP written here has 24 or 32 bits per pixel. 16-bit PNGs from photo and scientific software are reduced to 8 bits per channel.

Colour: RGB, greyscale, or an indexed palette of up to 256 colours in the PNG; BMP supports RGB or an indexed palette, written here as 8-bit sRGB.

Transparency: the PNG stores it as a full alpha channel, so edges and shadows can fade smoothly; the BMP keeps it as an optional fourth byte in 32-bit files, which many programs ignore.

Metadata: the PNG can carry text chunks, an ICC profile, physical resolution and EXIF in an eXIf chunk; BMP can carry nothing beyond the header's resolution fields (and a colour profile in rare V5 headers), but nothing is copied across.

PNG stores pixels losslessly with full alpha transparency. It is ideal for screenshots, logos, UI and anything with sharp edges, but photos saved as PNG are several times larger than JPEG.

A PNG opens with an 8-byte signature and is a chain of chunks, each with its own CRC: IHDR (size, depth, colour type), optional PLTE and tRNS for palettes, one or more IDAT chunks with the compressed rows, and IEND.

PNG files usually come from screenshots, design exports, logos and web graphics.

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 is the better choice for legacy software and embedded systems that require it, while PNG suits screenshots, logos, graphics and anything that needs transparency.

BMP strengths: No compression artifacts; Read by very old and very simple software. Drawbacks to weigh: Enormous files; Poor support for transparency; No metadata.