User Guide

CHAPTER 13. FILTERS 148
Save gamma This adds a gAMA chunk to your PNG file which reflects the current
Gamma factor for your display (set globally for GIMP). Viewers with a different
display can compensate to ensure the image doesn’t look too dark or too bright.
Adding this chunk increases file size slightly.
Save layer offset If you are saving a single layer which has been shifted (offset) from
the top-left of the image, this will add a oFFs chunk to your PNG file to preserve
this offset factor in other viewers. Adding this chunk if it’s needed increases file
size slightly.
Save resolution This adds a pHYs chunk to your PNG which records the physical
resolution of the image. This is needed by GIMP and other viewers for printing or
actual size previews. Adding this chunk increases file size slightly.
Save creation time This adds a tIME chunk to your PNG which records the exact
date and time when the image was last saved. This will be preserved and can be
viewed in other applications. Adding this chunk increases file size slightly.
Compression This controls the amount of compression used to reduce the file size.
Larger numbers will usually reduce file size but will make saving slower. The
default (6) is often an acceptable compromise, but see below.
13.115 PNM
Overview
Allows you to configure settings for saving a PNM (Portable aNy Map) image. PNM
File Information
PNM isn’t actually a format in itself, but encompasses PBM (Portable BitMap) for
monochrome images, PGM (Portable Grayscale Map) for grayscale images and PPM
(Portable PixMap) for color images.
The only configurable parameter for PNM images is the way that data is formatted
either in ASCII (American Standard Code for Information Interchange) or raw (plain
bytes). The raw format will produce significantly smaller filesizes and is faster to read
and write.
13.116 Polarize
Our apologies
Sorry, but the help page for this item is not written yet. Can I help?
Yes you can! Please send a message to [e-mail] with polar as the subject
line. Feel free to also include documentation related suggestions or fix requests.
13.117 Prepare for GIF
Our apologies
Sorry, but the help page for this item is not written yet. Can I help?
Yes you can! Please send a message to [e-mail] with prep4gif as the
subject line. Feel free to also include documentation related suggestions or fix requests.