general

# ImageOptim Preferences

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You shouldn't need to change any of these.

## General preferences

Preserve file permissions, attributes and hardlinks

  Instead of deleting old file writing a new one with the same name, just replaces old file's content in-place. This ensures that all hardlinks, aliases, file ownership, permissions, extended file attributes will stay the same.

  It's slightly faster not to preserve permissions.

Backup original files before saving

  Will write copy of a file with `~` appended to its name. This makes optimisation a bit slower and litters your disk with backup files.

Remove optional chunks

  Keep it on if you optimise for web. Disable if you have special PNGs with extra metadata.

Strip EXIF markers from files

  Removes image metadata, such as color profile, exposure time, GPS coordinates, camera model and name of software used to create the file. Metadata is never removed from JPEG files larger than 1.3MB.

jpegoptim

## JPEGOptim

Enabled

  If checked, ImageOptim will try to optimise JPEG files.

Maximum quality

  If set to 100%, optimisation will be lossless.

  Anything below 100% will cause lower quality of files if they appear to have been saved with higher quality setting.

pngout

## PNGOUT

Enabled

  If checked, ImageOptim will try to optimise PNG files using PNGOUT.

  PNGOUT is not bundled with ImageOptim. It's a great tool, but the author of PNGOUT forbids redistribution of it, so you have to download PNGOUT yourself.

Optimisation type

  PNGOUT is very effective, but very slow. Use lower level if you're impatient.

Interrupt if takes too long

  PNGOUT may need a lot of time to optimise very large images. This option gracefully interrupts PNGOUT after 1 minute.

advpng

## AdvPNG

Enabled

  If checked, ImageOptim will try to optimise PNG files using AdvPNG tool.

Optimisation level
  AdvPNG is relatively fast, so you can use maximum level.

optipng

## OptiPNG

Enabled

  If checked, ImageOptim will try to optimise PNG files using OptiPNG tool.

Optimisation level

  Number of different setting combinations tested. It rarely makes sense to try them all.

Make images interlaced (progressive)

  Interlaced images look better when they're loaded partially, but usually interlace makes compression less efficient.

  This checkbox has three states: if checked, will force images to be interlaced. When mixed, it will keep file's interlace unchanged, unchecked will remove interlace from files.

gifsicle

## Gifsicle

Enabled

  If checked, ImageOptim will try to optimise GIF files using Gifsicle.

  GIF files will be changed to interlaced or non-interlaced automatically, whichever is smaller. In-file comments will be removed.

  Please note that Gifsicle works best with animated GIFs and non-animated GIFs rarely can be optimised

  For best compression, you should convert GIF files to PNGs (ImageOptim does not do that automatically).

jpegrescan

## JpegRescan

Jpegrescan is a script based on `jpegtran`. It uses creates JPEG files with unusual number of progressive scans to achieve better compression, but such files may not be compatible with all browsers.