[Scribus] Memory problems when document contains many large pictures

[Stefan Forster]

My experience shows that scribus shouldn't be used for many large pictures.
Opening a file can take hours, often ended by a crash.

Observing the memory consumption gives hints to the underlying problem:
- during load all computer memory and also the swap partition is filled
- probably this is used to store all pictures in bitmap format
- reason is probably faster rescale when pictures are in memory
- when I set the images preview to "low resolution", memory is freed

Digital cameras produce very large pictures. It is common to have  resulting
image resolution above 800 DPI.
On screen these pictures are very sharp even in "low resolution" mode.
These images consume lots of memory and slow down many operation of scribus.

My recommendations:

1) make image resolution for preview dependent on resulting DPI


2) give user a chance to load documents having too many large images. E.g.
load-dialog option "very low resolution".
Currently the image resolution after load is always "normal", independent of
the three possible settings:
- Setting all images to low resolution
- Document Settings - Tools - Images preview: low resolution
- Preferences - Tools - Images preview: low resolution

When producing output, the full resolution must be used.
I'm not sure whether recommendation 1) and 2) really helps to reduce memory
consumption...


3) separate the image loading into an asynchronous, lower priority thread.
When this thread has loaded all images of the current page it should load
near images during say 60 seconds - then finish.
So it would not load more images than used (adapted to computer speed and
image size). Many scribus operations would be much faster. On a dual-core
CPU the second core would load the images !

greetings
      Stefan
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