[Qgis-developer] Set default TIFF options for QGIS

MORREALE Jean Roc jr.morreale at enoreth.net
Sun Jan 16 08:09:32 EST 2011


I would like to talk about the default image's options used by QGIS's 
tools. The most used output format is TIFF in its simplest form, which 
is quite unfriendly when you look at the resulting space disk involved.

I suppose that the majority of this list like to fine tune their output 
(when given the choice by the GUI) but a big part of the general users 
doesn't know about all the possible options, the result is they soon get 
some gigabytes of data. It makes harder to copy the images on a usb key 
or to forward it on the networks, it also has a impact on 
visualization's performance.

A good politic would be to assume that every tiff created by QGIS should 
makes use of a few basic options to ease the work of the users, without 
having them noticing it or asking them about it. If the user choose 
personal options, they would overwrite the default ones.

For example :
- COMPRESS=PACKBITS, reduces the size by 50% and is supported by every 
gis software I can think of (LZW or DEFLATE are not, due to some patents 
- TILED=YES, enables to zoom close and pan without reloading the whole image
- TFW=YES, brings compatibility
- BIGTIFF=IF_NEEDED, enables their whole dataset to 
converted/interpolated/etc. without stopping for no apparent reason

This way, generic users gets a better QGIS's experience and the tiff 
expert still gets what he wants, no sacrifice for anyone.

More advanced choice could also be made, like the automatic creation of 
a screensize pyramid if the base image is big. When the user adds this 
image to his project, it loads in a second. It gives a better impression 
than having to wait for the loading.


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