[Scribus] File size using photos

[Craig Ringer]

Henry Hartley wrote:
> Nigel Ridley wrote:
>>> This is really a newbie question but I would really like to know:
>>> Does Scribus only use the part of a photo/graphic that is viewable
>>> in the graphic frame or does the whole photo/graphic get put into
>>> the end file size regardless of how much has been cropped out.
>>> Is that clear? If not - let's say I have a 2.5Mb .jpg that I put
>>> into a Scribus document. I then crop the .jpg as I only want a
>>> section of the photo in the finished document - is there still
>>> 2.5Mb of .jpg in the document?
>>>
>>> The reason I'm asking is that I want to make a small booklet
>>> available on my website for download but obviously want to keep
>>> the file size down to something reasonable (there will probably
>>> be several graphics in the finished document).
> 
> It appears that the final PDF will have the entire image in it.

That is correct, at least when resampling is off. I'm not sure if
Scribus crops the image if resampling is on or not.

There are several reasons for this behaviour:

	- If we include the whole image, and it's a JPEG source,
	  we don't have to re-compress it. This is a quality and
	  (for small crops) often size saving.

	- The image can be included in the file just once, and
	  differerent parts referenced from different places in
	  the file. You might use the left side on one side of
	  the page, and the right on another. You might use
	  part of the image as an inset in one place, and the
	  full size one later, etc. This can be supported without
	  making the file bigger by including the whole image in
	  the first place.

Scribus would probably benefit from some heuristics for image slicing -
when we should `cut up' the image and embed only the bits that're use,
and when the whole image is best embedded. Factors such as source image
type (we should be more reluctant to chop up images we can otherwise
embed without modification) and percentage image used would need to be
considered. However, I don't personally see this as a particularly
urgent feature.

--
Craig Ringer