Convert TIFF to JPG

TIFF is a container, not a format

Almost everything surprising about converting a TIFF comes from one fact: TIFF does not describe how the pixels are stored, it describes where to find out. A .tif can be uncompressed, LZW, Deflate, PackBits, JPEG or CCITT Group 4 fax; it can be colour, greyscale, bilevel or CMYK; 8, 16 or 32 bits per channel; with or without an alpha channel; arranged in strips or tiles; with rows stored top-down or bottom-up; and it can hold many images in one file. Two files with the same extension can have almost nothing in common, which is why TIFF support varies so much between programs.

Several of those get normalised on the way to JPEG, and it is worth knowing which. CMYK becomes RGB, because JPEG in practice is an RGB format and the picture has to be converted — done here without the press profile that a studio file was separated against, so the colours will be close and not exact. 16 bits per channel becomes 8, which is invisible in a finished picture and matters a great deal if you intended to keep editing: the extra bits are headroom for adjusting exposure and colour without banding, and they are gone. Transparency is flattened, because JPEG has no alpha.

A multi-page TIFF — the usual output of a document scanner or a fax — converts its first page only. There is no way around it in a single-image format: a twelve-page scanned contract needs twelve JPEGs, and this produces one. That is the most common disappointment on this page and it is worth checking before you assume the rest of the document failed.

What you gain is size, and the margin is usually enormous. An uncompressed TIFF stores every pixel literally — a 24-megapixel photograph is around 72 MB before anything else — so the same picture as a good-quality JPEG lands somewhere near 5 MB. For a scanned document at 300 DPI in colour, the ratio is frequently more dramatic still.

When you want something else

For a multi-page TIFF, use something that knows there are several pages. tiffsplit in.tif page_ from libtiff separates them, ImageMagick's magick in.tif out-%d.jpg writes one JPEG per page in a single command, and if the pages are a document rather than photographs they probably want to be one PDF rather than a folder of pictures.

For anything colour-critical, this conversion should not happen in a browser at all. A CMYK TIFF separated for a press carries an ICC profile describing what its numbers mean, and converting without applying it is guesswork — magick in.tif -profile sRGB.icc out.jpg does it properly, and libvips does the same at a fraction of the memory on very large scans. Scientific 32-bit TIFFs and anything with layers belong in the software that made them.