Convert PNG to BMP: Free Online Converter

PNG (Portable Network Graphics) is the web's standard lossless image format, using DEFLATE compression with support for 24-bit color and an 8-bit alpha channel. BMP (Bitmap) is Microsoft's uncompressed raster format that stores raw pixel data in a simple header-plus-rows structure, readable by every Windows application since version 3.0. Converting PNG to BMP strips the DEFLATE compression and alpha transparency, writing each pixel as a raw 24-bit RGB triplet with row padding to 4-byte boundaries.

This conversion targets legacy Windows software, embedded systems, and hardware controllers that require uncompressed bitmap input. The resulting BMP file preserves all color data from the PNG but discards the alpha channel (transparent pixels render against a solid background). File sizes increase substantially: a 200 KB PNG screenshot may produce a 2-5 MB BMP because compression is removed entirely.

Certain industrial control systems, medical imaging devices, and kiosk software only accept BMP because they lack PNG decoding libraries. These applications were developed when CPU cycles were expensive, and reading raw pixel rows was dramatically faster than running DEFLATE decompression. If you need to feed images into Windows CE terminals, PLC visualization panels, or legacy VB6/Delphi applications, BMP is often the only accepted format.

BMP is also the native clipboard format on Windows. Automation scripts that paste images via the Windows clipboard, screen capture pipelines that feed into older image analysis tools, and game modding workflows for pre-2000 engines all expect BMP input. The format's simplicity — a fixed header followed by raw pixels — makes it trivially parseable by custom code without any third-party library dependencies.

Sharp decodes the PNG's DEFLATE-compressed pixel data and alpha channel, composites transparent pixels against a white background, then writes the result as a 24-bit BMP file. The output uses the standard BITMAPINFOHEADER (40 bytes) with BI_RGB compression type (meaning no compression). Each pixel row is padded to a 4-byte boundary as required by the BMP specification. The conversion preserves the full 8-bits-per-channel color from the PNG source.