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| Parametric curves 2 |
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Posted by: Ottia Tuota - 07-30-2021, 09:04 AM - Forum: Extending the GIMP
- Replies (19)
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I return to my old love: parametric curves. You may remember that I wrote a plugin to draw parametric curves as Gimp's paths approximately. Now the plugin has a new version. It is so big overhaul that I prefer to start a new thread. I wish everybody would just forget the old one.
The new version 2.1 has a new approximation algorithm. Meanwhile I have learned something about plugin writing, and I also had my eye on how the extension Parametric Curves is done in Inkscape, and I hope that I now managed to make my plugin a little more user-friendly. Anyway, it is no longer so loaded with options nobody wants.
If you have in your plugins folder files 'parametric_curves.py' and 'simple_parametric_curve.py', please delete those. To get the new version (2.1), click the link
http://kmarkku.arkku.net/Parametric_curv...aster.html
scroll down and download the file for Parametric curves; this gives you the .zip file parametric_curves_2_1.zip. (There is another download button for Special curves, an update of an old version, but I talk now only about the Parametric curves.)
The .zip file parametric_curves_2_1.zip contains one file parametric_curve.py and a small file doc.pdf. When you unzip the .zip file and move the .py file to your user's plug-ins folder, and restart Gimp, you find in the menu at
Filters > Render > Parametric curves
three plugins:
- Parametric curve (cartesian)
- Parametric curve (polar)
- Parametric curve (read function from file)
The documentation file doc.pdf contains explanations and instructions. They are probably useful only if you try the third plugin. Otherwise you don't lose much if you skip the documentation and just go experimenting.
The first plugin is the basic form, and I talk only about that in this post. The other two I shall explain later.
Open the first plugin Parametric curve (cartesian). If you let the default values in the GUI be as they are and just press OK, you get a half circle, as large as can be fitted on the screen. I don't show it here: you know what a half circle is.
To get a better example, put in the GUI the following:
Changes from the defaults are:
name = astroid
x(t) = cos(t)**3
y(t) = sin(t)**3
start value for t = 0 (this is the same as default)
end value for t = 2*pi
the curve is closed
padding = 50
Then on the screen you get an astroid, fitted to fill the screen with a little padding. And it is a path, so all stroking is left to the user.
That is the idea. If you keep 'fit to window' as Yes, you get as large a curve as fits on the screen and the next field enables you to put some padding. But clicking 'fit to window' to No, you can control the size and placement with the three inputs 'x of the origo', 'y of the origo' and 'scale'.
<...skip on first reading...>
There is one input which you can usually safely just ignore: custom parameter values. But I explain the idea for once: Consider the astroid example. There are four cusps. The plugin puts one anchor at each cusp. Those anchors should be set rather precisely to obtain a faithful rendering of the astroid. But how does the plugin find the cusps? It cannot compute derivatives (which would bring the problem down to solving equations). No, the only thing it can do is to run along the curve and examine it at very many close points. That is what it does and that is how it finds cusps (or inflection points or whatever). You understand that that is necessarily inaccurate. So, the idea in those custom points is that the user can help the plugin in its work. The user can list the parameter values (pi/2, pi, 3*pi/2) which give three of the cusps (the fourth is the starting or ending value of t, so the plugin knows it anyway). When the plugin is given those exact parameter values it places anchors at those exact spots and the result will be more accurate.
But in its current form the plugin is so good in finding cusps on its own (or inflection points or whatever) that you can usually ignore this difficulty. But it is good to know just in case: with custom points you can force the plugin to place anchors at some particular points. Then those points will be exactly on the right curve. Between the anchors the curve will only approximate the true curve.
</...skip on first reading...>
You may recall that the goal of this plugin is: Given a parametric curve,
1. approximate it with a path (a composite Bezier curve);
2. try to do this very accurately; and
3. do this with only a small number of control points.
Requirements 2 and 3 are contradictory, but at the moment I am rather pleased with how the plugin works.
If you try the plugin with complicated curves you are likely to find trouble cases where something goes wrong. I shall be grateful if you report those: the functions, the interval, custom points (if any), and any error messages.
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| Erase problems |
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Posted by: Robert Foster - 07-29-2021, 03:13 PM - Forum: General questions
- Replies (6)
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Hi I am new to this forum but not new to Gimp.
I do a lot of blending photos and recently I am having issue with erasing. All my older image projects still work fine, but when every I input newer photos as an original project or on top of an older project. Well they won't erase properly. What is happing is erase seems to be getting replaced by a color and this has completely stopped my work flow.
Mac/OS Big Sur 11.4
Gimp 2.10
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| Programmatically change text |
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Posted by: DontCallMeLarry - 07-27-2021, 08:04 PM - Forum: General questions
- Replies (3)
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Hi,
I'm trying to figure out how to programmatically change text in a layer and then save the output?
My use case is trying to add a version number (aka limited edition) to a digital photograph. I would like to do this 100 times and have an end result of 100 images that have a minor change of 1/100, 2/100, ... 100/100.
Thank you for the help or suggestions!
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| Making images with 300 dpi |
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Posted by: snowforest - 07-27-2021, 08:37 AM - Forum: General questions
- Replies (15)
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The images draw with librecad, when I export it as jpg, it only exports with 96 dpi. But I need 300 dpi. I turn it into 300 dpi using gimp. What do you suggest? Is gimp the best one to do it or another software or it doesnt matter? I use windows 10.
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| Reducing image size in gimp vs other program |
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Posted by: snowforest - 07-27-2021, 08:34 AM - Forum: General questions
- Replies (2)
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If I reduce the size of an image with gimp vs another program, to the same size (just the scale or resize thing), why does the quality look different? For example I have an image I reduced its size with gimp. The lines looked faded a little. Then I tried reducing the size of same image with ms office picture manager. The lines looked less faded. Am I doing something wrong or is it normal?
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| How to check if we save with iptc option |
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Posted by: snowforest - 07-27-2021, 04:52 AM - Forum: General questions
- Replies (6)
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If I save the image in jpg format with iptc data checked, after closing it, how , from where, can I review that iptc data later? Where is that data stored? How can it be viewed?
And do you recommend to check that option while saving and if so why?
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| GIMP 2.10 - Disable (Ctrl + MMB) Zoom??? |
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Posted by: chippy - 07-26-2021, 11:47 AM - Forum: General questions
- Replies (6)
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I liked Gimp 2.8, but have upgraded to Gimp 2.10 thinking it would preserve the original functionality but I am finding it to be extremely difficult to use.
Especially the way Gimp 2.10 forces the zoom mode when pressing ctrl + MMB.
How can I disable this and go back to ctrl + MMB to simply pan the image?
I can find no option, no forums discussions, no hacks or any way to disable this useless feature and it has absolutely killed my efficiency. Also this new canvas rotation feature is forced always on and is a similar conflicting hotkey which also destroys efficiency - I never once needed rotate canvas but now I keep rotating my canvas and it is horrible. I just want simple controls, or a way to disable these truly awful hotkey assignments.
In my opinion "more is not always better" especially when the developer forgets to add options to turn it off.
I am using gimp less now because of this horrible UX. It makes me very upset to see such a poorly designed update. I am at the point I just want to downgrade back to 2.8 and start moving away from Gimp entirely - It feels like Adobe is paying the developers of Gimp to degenerate the tool so to eliminate the competition - forget about donating to Gimp anymore, it is going backwards and losing its edge (just like so many other free software).
Just wanted to voice my frustrations because I know it would take a competent developer less than an hour to add options to shut off these ridiculous new-age features.
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