general

# ImageOptim Preferences

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You shouldn't need to change any of these (except path to PNGOUT if you've installed it).

## 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.

Number of tasks run at once

  If you have multi-CPU or multi-core system running more than one task at the same time will speed things up a lot.

Run tasks with lower priority

  This will prevent whole system from feeling sluggish during optimisation.

jpegoptim

## JPEGOptim

Enabled

  If checked, ImageOptim will try to optimize JPEG files.

JPEGOptim path

  Path to `jpegoptim` executable file. Usually `/usr/bin/jpegoptim` or `/sw/bin/jpegoptim`.

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.

Strip Comments from files
Strip EXIF markers from files

  Removes image metadata, like name of program or model of camera which created the file.

pngout

## PNGOUT

Enabled

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

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

PNGOUT path

  Path to `pngout` (or `pngout-darwin`) executable file.

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 optimize very large images. This option gracefully interrupts PNGOUT after 1 minute.

Remove optional chunks

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

pngcrush

## PNGCrush

Enabled

  If checked, ImageOptim will try to optimize PNG files using PNGCrush.

PNGCrush path

  Path to `pngcrush` executable file.

Try fixing damaged files

  PNGCrush will not reject PNG files that have invalid checksums

Remove chunks

  PNG stores information in chunks and many of them are optional. Enter 4-letter names of chunks you wish to remove or press `γ` button to pre-fill list with gamma-related chunks.

advpng

## AdvPNG

Enabled

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

AdvPNG path

  Path to `advpng` executable file. Usually `/usr/bin/advpng` or `/sw/bin/advpng`.

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

optipng

## OptiPNG

Enabled

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

OptiPNG path

  Path to `optipng` executable file. Usually `/usr/bin/optipng` or `/sw/bin/optipng`.

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 optimize GIF files using Gifsicle.

Gifsicle path

  Path to `gifsicle` executable file.

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 optimized

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