Hi,

Marco writes:

I would like to ask some gimp-questions...

1) What algorithm is used to resize images in the GIMP? Is there something like Paint Shop Pro's "smart resize"?

We can't tell you unless you tell us what Paint Shop Pro's "smart resize" does.

2) There is no preview for the unsharp mask filter. Is it true?

True for GIMP 2.0. There is however a preview in the development version so GIMP 2.2 will have one.

3) The menu (and dialogs) font is sooo small (i use debian). Have you experienced something similar?

Are you using the Small theme? If you've choosen the Small theme from the preferences dialog, you might experience very small fonts. The problem here is that gtkrc files only allow to set absolute font sizes. The font size we've choosen to hardcode in the Small theme is a reasonable choice if, and only if, your X server display resolution is properly setup. If the X server reports a wrong display resolution you may end up with a very small font. I'd suggest you fix your X server setup, and if that doesn't help, you edit the theme file and hardcode a larger font there.

If you aren't using the Small theme, you simply need to change the font-size for GTK+ applications. If you are running GNOME, you can set that in the Desktop Preferences, otherwise you need to edit your ~/.gtkrc-2.0 file.

Sven

Hello,
I'm using Debian and had a similar problem a while ago. If I remember correctly, it happened because I was doing "startx -- :1" instead of the normal startx. When doing that, I got really small fonts in gtk2 apps. I figured out why it was happening (can't remember now, though) and found that I needed to set my dpi to 100. I now use "startx -- :1 -dpi 100". So, if you're launching X in a non-standard way, you may want to give this a shot.
Ben

On Sun, Oct 10, 2004 at 12:22:20PM +0200, Sven Neumann wrote:

Hi,

Marco writes:

I would like to ask some gimp-questions...

1) What algorithm is used to resize images in the GIMP? Is there something like Paint Shop Pro's "smart resize"?

We can't tell you unless you tell us what Paint Shop Pro's "smart resize" does.

2) There is no preview for the unsharp mask filter. Is it true?

True for GIMP 2.0. There is however a preview in the development version so GIMP 2.2 will have one.

3) The menu (and dialogs) font is sooo small (i use debian). Have you experienced something similar?

Are you using the Small theme? If you've choosen the Small theme from the preferences dialog, you might experience very small fonts. The problem here is that gtkrc files only allow to set absolute font sizes. The font size we've choosen to hardcode in the Small theme is a reasonable choice if, and only if, your X server display resolution is properly setup. If the X server reports a wrong display resolution you may end up with a very small font. I'd suggest you fix your X server setup, and if that doesn't help, you edit the theme file and hardcode a larger font there.

If you aren't using the Small theme, you simply need to change the font-size for GTK+ applications. If you are running GNOME, you can set that in the Desktop Preferences, otherwise you need to edit your ~/.gtkrc-2.0 file.

Sven

Hi,

Marco writes:

Paint Shop Pro has an option called "Smart Resize" which automatically uses bicubic resampling when enlarging, and bilinear when reducing. What resizing algorithm is used by th GIMP? I think that reducing the size to one half it doesn't limit to get one pixel in a 2x2 square.

It uses the algorithm you specify in the Scale tool or the Scale dialog respectively.

I use: Gimp 1.2, Gtk Lib 2.2.0, IceWm (no GNOME or KDE). I can't find any selection for a "Small theme".

It's about time that you update to GIMP 2.0 then. GIMP 1.2 is outdated, unmaintained and unsupported.

Sven

* Marco :

Barton Bosch wrote:

Hey Marco, could you tell whether and why using bicubic for enlarging and bilinear for reducing is better than using bicubic for both? I was under the impression that bicubic was the highest quality algorithm for all resizing operations.

No, I couldn't. I cannot find any reason based on a clear mathematical proof.

However I'm quite sure that bicubic is not a panacea for all resizing operations. In

http://www.msjc.edu/m2/gall/resampling-nearest&bilinear/resampling.html

is given an example of better results with "Nearest Neighbour" instead of bicubic (because of the image nature).

In

http://www.mav-magazine.com/Apr1999/resample/

is described this bilinear/bicubic option of PSP.

The question is tricky. And I'm very interested in a clear answer. My opinion is that (sometimes) bicubic for reducing smooths the image too much.

I found this off comp.periphs.scanners: http://www.xs4all.nl/~bvdwolf/main/foto/down_sample/down_sample.htm

Though it doesn't tell about 'real-life' performance (PS CS's will likely produce 'sharper' looking image), it seems ImageMagick does the better thing.

psavo@iki.fi (2004-10-15 at 0609.12 +0000):

The question is tricky. And I'm very interested in a clear answer. My opinion is that (sometimes) bicubic for reducing smooths the image too much.

I found this off comp.periphs.scanners: http://www.xs4all.nl/~bvdwolf/main/foto/down_sample/down_sample.htm

Another similar pages talking about filtering (demo and/or code) just in case someone wants to get deeper:

http://www.binbooks.com/books/photo/i/l/57186AF8DE http://www.antigrain.com/
http://www.path.unimelb.edu.au/~dersch/interpolator/interpolator.html http://www.xmission.com/~legalize/zoom.html

Basically, there are better methods than current GIMP ones (or some other common apps, for that matter). Search yourself, not the first time the issue of best quality (transformations, noise, colour, etc) appears in GIMP lists.

Though it doesn't tell about 'real-life' performance (PS CS's will likely produce 'sharper' looking image), it seems ImageMagick does the better thing.

Well, the typical approach to test signal processing systems is to use some kind of "simple" input, mostly cos it is easier to compare with output.

GSR

Hi,

GSR - FR writes:

Another similar pages talking about filtering (demo and/or code) just in case someone wants to get deeper:

http://www.binbooks.com/books/photo/i/l/57186AF8DE http://www.antigrain.com/
http://www.path.unimelb.edu.au/~dersch/interpolator/interpolator.html http://www.xmission.com/~legalize/zoom.html

Perhaps you could add these links to our Wiki?

Sven