Editing Lossy compression (section)

====JPEG====
The primary programs for lossless editing of JPEGs are <code>[[jpegtran]]</code>, and the derived <code>exiftran</code> (which also preserves [[Exif]] information), and [http://sylvana.net/jpegcrop/ Jpegcrop] (which provides a Windows interface).

These allow the image to be [[Cropping (image)|cropped]], rotated, [[flipped image|flipped]], and [[flopped image|flopped]], or even converted to [[grayscale]] (by dropping the [[chrominance]] channel). While unwanted information is destroyed, the quality of the remaining portion is unchanged.

Some other transforms are possible to some extent, such as joining images with the same encoding (composing side by side, as on a grid) or pasting images such as logos onto existing images (both via [http://sylvana.net/jpegcrop/jpegjoin/ Jpegjoin]), or scaling.<ref>{{Cite web|url=http://sylvana.net/jpegcrop/jpegtran/|title=New jpegtran features|website=sylvana.net|access-date=2019-09-20}}</ref>

Some changes can be made to the compression without re-encoding:
* Optimizing the compression (to reduce size without change to the decoded image)
* Converting between progressive and non-progressive encoding.

The freeware Windows-only [[IrfanView]] has some lossless JPEG operations in its <code>JPG_TRANSFORM</code> [[Plug-in (computing)|plugin]].