[Courses][gimp] Tux, image formats, and a drag-n-drop tip

Akkana Peck akkana at shallowsky.com
Sun Feb 20 12:34:51 EST 2005

Jon Drews writes:
>  I realize I am a little behind here but a few quick questions:
> 1) I should always save in the native *.xcf before doing alterations?
> I did that with this image.

It never hurts, but you don't really need to save as .xcf unless
you're using multiple layers, or have other gimpish things like
a complicated selection that you don't want to lose.  Otherwise,
just making a copy of the original .jpg or whatever is fine.
(But do that from the shell: cp img.jpg img-orig.jpg or similar.
Don't read the file into gimp then save back as jpg unless you're
making changes.  JPG is "lossy", which means that every time you
read it in then write it out again, you lose a little bit of quality,
so don't do that any more times than you have to.)

If you want to store an intermediate version but you don't need
layers, use png or tiff (I recommend png).  They're much bigger
than jpg but they're not lossy.

My overview of image formats: http://shallowsky.com/linux/imageformats.html

> 2) These images were large so I worked on them in their original large
> size and then reduced them using the techniques from lesson 1. Is that
> the proper thing to do or should I reduce them first? Which sequence
> gives better image quality: alter first and then reduce or reduce and
> then alter ?

Most of the time, working at full size and reducing at the very end
gives better quality.  There are a few cases where that might not
be true: rescaling text or intricate line drawings sometimes makes
the result look "jaggy", so if you're going to add text or drawings
it may be better to rescale the image before adding them.

>   I must say this really quite a good course Akkana. Thanks!

Thanks!  I'm glad you like it.

Patricia Peck writes:
> I went looking for Tux in Google Images, and found many, many versions 
> of him.  Some were .jpg, some were .png, some were .gif, and they were 
> of many different sizes -- does it matter which you use for working on 
> in the gimp?  Are some better in quality than others in the final product?

The "imageformats" page I mentioned above should give some background
on the formats: since Tux only has a few colors, gif or indexed png
is usually the most efficient format for him, but if you add him
to a full color photograph, you're best off saving the
end result as jpg.

But talking about searching Google Images seems like a good time to
introduce a hot gimp tip: Drag 'n' drop!

Both mozilla and gimp are quite smart about drag-n-drop, so if you
have gimp open, you can drag from any image being displayed in a
mozilla-based browser and drop onto the gimp toolbox, and the image
will open in gimp.  (I don't know if konqueror supports d-n-d or not.)

Of course, you want to be looking at the full sized image in the browser;
if you drag a thumbnail, the thumbnail is what gimp will open.

You can even drag from mozilla into a current gimp image window,
and gimp 2 will make a new layer consisting of that image.

I hear middleclick-paste onto the gimp toolbox window is supposed
to work in CVS versions of gimp (just like it does in mozilla --
middleclick on the window opens the selection as a filename or url),
but that doesn't work in current versions yet.


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