BMP to TIFF Converter

BMP and TIFF can both hold exact, lossless pixels, but TIFF is the one printers, publishers, scanners, fax and archive systems ask for: it records a print resolution, compresses losslessly and can hold several pages. This converter decodes each bitmap with your browser — 1- to 32-bit, RLE and OS/2 BMPs — and writes a baseline TIFF with LZW, Deflate or no compression.

How to use this tool

1. Drop one or more .bmp files.
2. Choose LZW (the safe default), Deflate (usually smallest) or None.
3. Keep the bitmap's own resolution or set one such as 300 DPI; keep or fill transparent areas of 32-bit BMPs.
4. Optionally combine all images into one multi-page TIFF, then download.

Formula

TIFF = 8-byte header ("II", 42, first directory offset) + per page an image file directory (width, height, 8-bit samples, compression, RGB, strip offsets and sizes, X/Y resolution in inches) + ~64 KB strips.

The resolution stored in the BMP (pixels per metre) is converted to DPI and kept unless you choose another one. With LZW or Deflate each row is stored as differences between neighbouring pixels (predictor 2) before compression; LZW follows the same code rules as libtiff. Bitmaps with an alpha channel become RGBA TIFFs.

Example

An uncompressed 24-bit 160 × 100 BMP is 48,054 bytes; as an uncompressed TIFF it becomes 48,192 bytes (8 + 162 + 22 bytes of header and tags plus 48,000 bytes of pixels). With LZW, flat-coloured graphics shrink to a small fraction of that, while noisy photos shrink only a little.