Why is the BMP so much larger than the PNG?

BMP stores every pixel without compression, so the byte count is roughly width times height times three, plus row padding. PNG runs the same pixels through DEFLATE, which is why the bitmap comes out several times bigger.

What happens to transparent areas?

A 24-bit BMP has no alpha channel. Transparent and semi-transparent pixels are blended onto white as the file is written, so a logo on a clear background ends up on a solid white field.

Does the picture itself change?

No resampling or color reduction happens. Each opaque pixel is copied straight across; only the container, the compression, and the flattening of alpha differ from the PNG.

What bit depth is the output?

Always 24 bits per pixel, eight each for red, green, and blue, written in BMP's bottom-up BGR row order with four-byte row padding per the BITMAPINFOHEADER format.

Can I feed it a JPG instead of a PNG?

Yes. Any image the browser can decode works as the source; it is redrawn onto the canvas and encoded as a BMP the same way.

Is anything uploaded to a server?

No. Decoding the PNG and writing the BMP both happen in the browser, so the file never leaves your device.

PNG to BMP

Writes your PNG out as an uncompressed 24-bit BMP. Transparency flattens onto white.

What this does

A BMP file stores pixels one row at a time with no compression, so a bitmap holds raw color values exactly as a decoder hands them over. PNG, by contrast, wraps the same pixels in lossless DEFLATE compression and an alpha channel. Going from PNG to BMP unpacks that compression into a flat 24-bit grid: three bytes of blue, green, and red per pixel, padded to a four-byte boundary at the end of every row.

This converter decodes the PNG in your browser, paints it onto a canvas, and writes the result as an uncompressed 24-bit BMP. Because 24-bit BMP carries no alpha, any transparent or semi-transparent pixels are composited onto a white background as the file is written. The decode and the byte-level encode both run on your own machine, so the image is never sent anywhere.

How it works

1Drop a PNG, or click to pick one.
2It is redrawn onto a canvas and written out as a 24-bit BMP.
3Download the BMP, keeping the original file name.

Built on web standards

Built with standard browser APIs — no third-party libraries.

Frequently asked questions

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