Re: [Gimp-developer] preview window does not work
On Fri, 09 Mar 2007 08:36:46 +0100, Sven Neumann [EMAIL PROTECTED] wrote: Hi, On Fri, 2007-03-09 at 08:08 +0100, [EMAIL PROTECTED] wrote: I did some revectoring and tidy up work on the convolution plugin last year and got told off for not testing it and introducing bugs. It turned out the bugs have been there since 1997. My objective was to make the code more readable and maintainable and to generalise the matrix routines to handle larger dimensions. I did not attempt to fix these anomolies. Huh? Your changes got committed, if I remember correctly. Yes the readability and cleanup that I did got committed, it is now more readable and maintainable. I did not attempt to fix a couple of oddities that I noticed (and that Bill initially thought I had introduced). GG, can you perhaps consider to take your bashing off-list? We all know very well that the GIMP code is far from perfect. A lot of plug-ins and also some code in the core is old and the people who wrote it weren't experts in computer graphics. The algorithms being used are sometimes badly chosen and sometimes even incorrectly implemented. There is a lot to do in this respect and we hope that the switch to GEGL will force us to review all this code. The concepts of GEGL and babl should also allow us to get to cleaner and more readable code. Please do not discourage us and potential contributors by continously pointing out that some of the code is crap. We all know that. Sven Well it seems it was you who got Luis back up as soon as he came in but thanks for having a more positive to things generally in your recent posts. I was aiming to forewarn him about the bugs and the state of the code I was refering him to, to prevent him wasting further time and getting more frustrated. In the past I have seen too many attempts to improve things dismissed out of hand as either not being a problem or being a waste of time. If we take the more realistic approach you outline above things will certainly move forwards and ppl will know where they are. gg ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
Concerning the plug-in example, if you want to see the proper way to do it, you can look at the real blur plug-in, in plug-ins/common/blur.c. However, as Sven suggests, that plug-in only does a 3x3 blur, and a proper implementation for NxN, as in the example, would be pretty hard to read -- too hard to make a good example. -- Bill __ __ __ __ Sent via the CNPRC Email system at primate.ucdavis.edu ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
My plugin is working fine, after I found my bug and the one in the blur example. It's just annoying. Then please explain the bug in the example code and send us a patch (preferably against SVN) that we can apply so that others won't run into the problem again. http://svn.gnome.org/viewcvs/gimp-web-devel/trunk/writing-a-plug-in/ Unfortunately, the code has more that one bug, or the correction I made didn't solve the issue completely. Using your last code in http://svn.gnome.org/viewcvs/gimp-web-devel/trunk/writing-a-plug-in/3/myblur5.c?revision=207 (that still shows the shift), I did an experiment. First, I made a symmetric image with a set of lines: http://w3.impa.br/~luis/fotos/lixo/grid.jpg and then blurred it with the code and radius=20. I got this: http://w3.impa.br/~luis/fotos/lixo/grid_blurred.jpg You can see three problems: 1) The old 1-pixel-down shift. 2) The two dark bands (20 lines each) at top and bottom of the image. 3) Even much intriguing is the grey band right below the top one, also of 20 lines! And it is homogeneous (no likes inside)... My 'solution' (change 'x1, y1,' in line 241 by 'x1, y1+1,') took care of the shift, but not of the banding. The homogeneous grey band just moved to the bottom... (you cannot imagine the mess this does in my code!) I think that the problem is that this shuffle function is implemented without taking into account the drawable height. Now: Could anyone please show me a SIMPLE code where the tile handling is properly implemented, without bugs? I mean, the same blurring plugin would be just perfect, but without bugs... From this buggy example, I just don't understand how they work, so I am not able to find the bug. You should realize that this is all just volunteers effort. Someone wrote this tutorial years ago and another volunteer added it to the gimp-developer web site. It will take another volunteer to improve it and to fix the example code. And yet even more volunteers will have to show up in the future to keep the tutorial uptodate. Of course I understand this. We are all volunteers. This was not the point. Anyway, thank you for your time, Luis. ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
Quoting Luis A. Florit [EMAIL PROTECTED]: http://w3.impa.br/~luis/fotos/lixo/grid_blurred.jpg You can see three problems: 1) The old 1-pixel-down shift. 2) The two dark bands (20 lines each) at top and bottom of the image. 3) Even much intriguing is the grey band right below the top one, also of 20 lines! And it is homogeneous (no likes inside)... My 'solution' (change 'x1, y1,' in line 241 by 'x1, y1+1,') took care of the shift, but not of the banding. The dark bands can be attributed to the fact that the averaged region near the borders is filled out by effectively duplicating the row or column at the edges. The algorithm may not be optimal, but it works as one should expect. The average is currently produced by a formula similar to: sum (v-2, v-1, v, v+1, v+2) / 5 Near the borders, when there is no value v+2 available, for example, you end up with: sum (v-2, v-1, v, v+1, v+1) / 5 And the next pixel will be: sum (v-2, v-1, v, v, v) / 5 If you wish to improve the algorithm, I would suggest that you need to discard terms and adjust the denominator accordingly -- the last example shown should produce sum (v-2, v-1, v) / 3. At least, that is my recommendation. I am not a mathematician. ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
On Fri, 09 Mar 2007 05:31:26 +0100, [EMAIL PROTECTED] wrote: Quoting Luis A. Florit [EMAIL PROTECTED]: http://w3.impa.br/~luis/fotos/lixo/grid_blurred.jpg You can see three problems: 1) The old 1-pixel-down shift. 2) The two dark bands (20 lines each) at top and bottom of the image. 3) Even much intriguing is the grey band right below the top one, also of 20 lines! And it is homogeneous (no likes inside)... My 'solution' (change 'x1, y1,' in line 241 by 'x1, y1+1,') took care of the shift, but not of the banding. The dark bands can be attributed to the fact that the averaged region near the borders is filled out by effectively duplicating the row or column at the edges. The algorithm may not be optimal, but it works as one should expect. The average is currently produced by a formula similar to: sum (v-2, v-1, v, v+1, v+2) / 5 Near the borders, when there is no value v+2 available, for example, you end up with: sum (v-2, v-1, v, v+1, v+1) / 5 And the next pixel will be: sum (v-2, v-1, v, v, v) / 5 If you wish to improve the algorithm, I would suggest that you need to discard terms and adjust the denominator accordingly -- the last example shown should produce sum (v-2, v-1, v) / 3. At least, that is my recommendation. I am not a mathematician. ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer yes the border handling is pretty basic. YOu could look at the convolution filter (one of the plugins built with gimp) for different methods of dealing with borders. The basic problem is that this will always be extrapolation outside the real data so its a guess. With a pattern like your grid this can easily be badly wrong. The best simple method would be a linear extrapolation over a few points. This would at least prevent a black line becoming a black band as you are seeing here. Another approach would be to not process areas with unknown data, ie leave a band unblurred and then replace this with an extrapolation of the edges of the reduces area containing correct data. This will provide more visually acceptable results in your test case although this can never be mathematically rigourous since you are arbitarily extrapolation outside known data. This may well be an approach worth investigating throughout gimp since current methods seem to be somewhat rudementary. gg ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
On Thu, 08 Mar 2007 23:13:08 +0100, Luis A. Florit [EMAIL PROTECTED] wrote: My 'solution' (change 'x1, y1,' in line 241 by 'x1, y1+1,') took care of the shift, but not of the banding. The homogeneous grey band just moved to the bottom... (you cannot imagine the mess this does in my code!) This is what's known in the trade as a frig factor! You are arbitarily making an adjustment to correct one subjective error. You will likely find that on a different image it bahaves differently unless you understand why this adjustment is necessary and that +1 is a generally valid fix. I cant comment on whether this is a bug in the tile code of the example or elsewhere. I suggest you look at some of the built in plugins. I think most of the effects on the filters menu are implemented as plugins that are part of the gimp distribution. There are some differences in integrating external plugins but it's pretty much the same thing in the plugin code so you may be able get some clues on what you are trying to do from the existing plugins. Be warned there are bugs in there two ;) I did some revectoring and tidy up work on the convolution plugin last year and got told off for not testing it and introducing bugs. It turned out the bugs have been there since 1997. My objective was to make the code more readable and maintainable and to generalise the matrix routines to handle larger dimensions. I did not attempt to fix these anomolies. My initial idea was to write a new plugin but I gave up since the documentation was totally inadequate, out of date and sometimes inaccurate. I decided it would take more time than I had available. I hope you have more luck. gg ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
Hi, On Fri, 2007-03-09 at 08:08 +0100, [EMAIL PROTECTED] wrote: I did some revectoring and tidy up work on the convolution plugin last year and got told off for not testing it and introducing bugs. It turned out the bugs have been there since 1997. My objective was to make the code more readable and maintainable and to generalise the matrix routines to handle larger dimensions. I did not attempt to fix these anomolies. Huh? Your changes got committed, if I remember correctly. GG, can you perhaps consider to take your bashing off-list? We all know very well that the GIMP code is far from perfect. A lot of plug-ins and also some code in the core is old and the people who wrote it weren't experts in computer graphics. The algorithms being used are sometimes badly chosen and sometimes even incorrectly implemented. There is a lot to do in this respect and we hope that the switch to GEGL will force us to review all this code. The concepts of GEGL and babl should also allow us to get to cleaner and more readable code. Please do not discourage us and potential contributors by continously pointing out that some of the code is crap. We all know that. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
Hi, On Thu, 2007-03-08 at 19:13 -0300, Luis A. Florit wrote: Unfortunately, the code has more that one bug, or the correction I made didn't solve the issue completely. I think we should then replace the example by something simpler. The point of this tutorial is not to show how to implement a blur. It is supposed to show some basic concepts of plug-in development. The code that is used as an example should be simple and bug-free. The current blur code doesn't seem to fulfill these requirements. So perhaps it should be replaced by a more local operation. Another option would be to add a comment to the tutorial that points out that, for the sake of simplicity, the blur code is simpler than it would have to be and that it introduces a shift for that reason. Now: Could anyone please show me a SIMPLE code where the tile handling is properly implemented, without bugs? I mean, the same blurring plugin would be just perfect, but without bugs... From this buggy example, I just don't understand how they work, so I am not able to find the bug. The GIMP source code includes more than hundred plug-ins. I am sure you will find one or two that can serve as examples. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
On Wed, 07 Mar 2007 08:53:34 +0100, Sven Neumann [EMAIL PROTECTED] wrote: 3) Ok, this is the serious one: The whole blurred region is shifted 1 pixel down. To check this, create a new white image with a single black pixel in the middle, and blur it with radius=1. Go back and forth and you will see the 3x3 gray square shifting down. Again, how is that a problem? This example code is meant to illustrate some concepts of GIMP plug-in development, in particular how to add a preview to your plug-in window. It is not meant to perform any useful image manipulation. How is it a problem that there are these small and varying offsets all the way through gimp? I suspect this is not so much a bug in the example code, which as you say is just an example, but in gimp itself. I have already submitted bugs comments indicatiing significant drift in scaling with NONE interpolation, there is residual drift in lanczos that I dont believe comes from the scaling code , there are fiddle factors to correct offsets in a number of areas. Rather than dismissing this report, it may serve as a useful means of triangulating to find the root cause of some of these drifts. If scaling, rotation and now plugins show drift it should help eliminate the superficial code and enable tracking this back to the problems in the core. This is only gut feeling on my part but it seems that the evidence is mount to confirm what I suggested six mounths ago when I first started looking at lanczos. Thanks to Luis for taking the time to notify the apparent error. gg ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
Hi, On Wed, 2007-03-07 at 09:55 +0100, [EMAIL PROTECTED] wrote: How is it a problem that there are these small and varying offsets all the way through gimp? I suspect this is not so much a bug in the example code, which as you say is just an example, but in gimp itself. If you can point out how this can be a bug in gimp itself, I would love to hear about it. We have several hundreds of plug-ins that work correctly so it is rather unlikely that there's a bug in the core or libgimp that would be responsible for this offset. The fact that there's an offset here and a drift in the transform code in the core is pure coincidence. I wonder what makes you think that there's a relation. Off-by-one and rounding errors are not uncommon and they happen all over the place. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
On Wed, 07 Mar 2007 08:53:34 +0100, Sven Neumann [EMAIL PROTECTED] wrote: 3) Ok, this is the serious one: The whole blurred region is shifted 1 pixel down. To check this, create a new white image with a single black pixel in the middle, and blur it with radius=1. Go back and forth and you will see the 3x3 gray square shifting down. Again, how is that a problem? This example code is meant to illustrate some concepts of GIMP plug-in development, in particular how to add a preview to your plug-in window. It is not meant to perform any useful image manipulation. PS. Blur off the menu does not seem to reproduce this. So either its a buggy example as Svan suggests or a drift in the plugin interface. A quick check on rotation shows 1px drift in x and y. Create a 20x20 and a 21x21 canvas put a pencil tool (11 circle) spot and rotate 90 degrees about the centre of the dot. Preview gets it right but it moves when committed. Also odd effects around borders The offsets seem to be independant of interp method. A non-exhaustive check on on scaling seems not to show this offset but like I said I found I had to add fiddle factors to achieve this. I added some comments to code to attempt to explain what was happening but it was a bit hand wavy. My belief is that I am applying a correction to an offset coming from outside the scaling code. gg. ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
On Wed, 07 Mar 2007 10:02:38 +0100, Sven Neumann [EMAIL PROTECTED] wrote: Hi, On Wed, 2007-03-07 at 09:55 +0100, [EMAIL PROTECTED] wrote: How is it a problem that there are these small and varying offsets all the way through gimp? I suspect this is not so much a bug in the example code, which as you say is just an example, but in gimp itself. If you can point out how this can be a bug in gimp itself, I would love to hear about it. We have several hundreds of plug-ins that work correctly so it is rather unlikely that there's a bug in the core or libgimp that would be responsible for this offset. OK, then you're probably right , it's a buggy eg. and it would be best to give examples the work correcly to get ppl off to a good start. The fact that there's an offset here and a drift in the transform code in the core is pure coincidence. I wonder what makes you think that there's a relation. Off-by-one and rounding errors are not uncommon and they happen all over the place. Sven Obviously rounding errors are unavoidable when doing everything in integer arithmatic although I think quite a bit could be done to reduce the accumulation of errors. However I was seeing a more significant offset on NONE that I detailed when I split the lancos offset bug (principally for this reason). gg ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
Hi, On Wed, 2007-03-07 at 11:03 +0100, [EMAIL PROTECTED] wrote: OK, then you're probably right , it's a buggy eg. and it would be best to give examples the work correcly to get ppl off to a good start. I already fixed the wrong use of gimp_progress_set_value() this morning. If someone wants to look into fixing or improving the examples and/or the tutorial, please do so. The code is found in the gimp-web-devel SVN module. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
Hi, On Wed, 2007-03-07 at 10:52 +0100, [EMAIL PROTECTED] wrote: A quick check on rotation shows 1px drift in x and y. Create a 20x20 and a 21x21 canvas put a pencil tool (11 circle) spot and rotate 90 degrees about the centre of the dot. Preview gets it right but it moves when committed. Also odd effects around borders The offsets seem to be independant of interp method. If you rotate by exactly 90 degrees, this is always done with INTERPOLATION_NONE, no matter what you select in the tool options. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
* El 08/03/07 a las 1:57, [EMAIL PROTECTED] chamullaba: In general just try to keep cool. You are perfectly right in complaining about being lead astray by a bad code example and in your place I would be equally pissed off about the time I had wasted. I'm sure dismissive comments don't to much to releave the frustration either. Hopefully your comments will lead to some corrections being made. This was not the problem: I didn't complain about bugs, I looked for an answer to a bug in my code that I finally found. I didn't want to send any bug report for such a thing. What pissed me off was that I was requested to send a bug report, and when I sent it, the same guy answered that it was ok the code to have bugs since it was for demo purposes only! BTW, I believe that this is one of the main reasons why Fedora is weakening fast: unattended bugs that are leading to an OS so full of bugs that people are simply abandoning it. That is sad, and certainly not good for Linux. Dont worry too much about the LibGimp-CRITICAL message. I am getting that as well, you are running a development version, presumably current svn, expect some errors and messages. My plugin is working fine, after I found my bug and the one in the blur example. It's just annoying. Thanks, Luis. ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
Hi, On Wed, 2007-03-07 at 22:18 -0300, Luis A. Florit wrote: My plugin is working fine, after I found my bug and the one in the blur example. It's just annoying. Then please explain the bug in the example code and send us a patch (preferably against SVN) that we can apply so that others won't run into the problem again. http://svn.gnome.org/viewcvs/gimp-web-devel/trunk/writing-a-plug-in/ You should realize that this is all just volunteers effort. Someone wrote this tutorial years ago and another volunteer added it to the gimp-developer web site. It will take another volunteer to improve it and to fix the example code. And yet even more volunteers will have to show up in the future to keep the tutorial uptodate. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
[Gimp-developer] preview window does not work
Pals, I made my first plugin in C for gimp, based on the one here: http://developer.gimp.org/writing-a-plug-in/3/index.html Unfortunately, this plugin has several bugs, that translated to my own, and I am not being able to detect them (is there any other source like the avove to get some base plugin to work on?) Sorry for the not very objetive question: The preview window updates when I change the parameters, but only in the top-left corner, where the preview appears. In the rest, it updates with some previous data, or some garbage. When I run the plugin for the second time, it is ok. That is, there is some buffer that is not being freed... Should I clean the region after a gimp_pixel_rgn_init call? Sometimes this also occurs on the main window. Thanks, Luis ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
I suggest to read the book Beginning Gimp written by Akkana Peck. Data structures aren't cleared automatically. You have to clear them yourself. Otherwise you have random garbage in your picture. This can happen but it mustn't happen always. On Tuesday 06 March 2007 18:16, Luis A. Florit wrote: Pals, I made my first plugin in C for gimp, based on the one here: http://developer.gimp.org/writing-a-plug-in/3/index.html Unfortunately, this plugin has several bugs, that translated to my own, and I am not being able to detect them (is there any other source like the avove to get some base plugin to work on?) Sorry for the not very objetive question: The preview window updates when I change the parameters, but only in the top-left corner, where the preview appears. In the rest, it updates with some previous data, or some garbage. When I run the plugin for the second time, it is ok. That is, there is some buffer that is not being freed... Should I clean the region after a gimp_pixel_rgn_init call? Sometimes this also occurs on the main window. Thanks, Luis ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
Hi, On Tue, 2007-03-06 at 14:16 -0300, Luis A. Florit wrote: http://developer.gimp.org/writing-a-plug-in/3/index.html Unfortunately, this plugin has several bugs If you can point out bugs in the tutorial, we would love to hear about them so that they can be corrected. What exactly do you think is incorrect? Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] preview window does not work
Hi, On Tue, 2007-03-06 at 23:04 -0300, Luis A. Florit wrote: These are the bugs I can remember now. Probably some of these are not bugs... apologies then. 1) The bottom bar of the main window becomes blue when the dialog appears. Looks like progress handling needs to be improved in the plug-in. It shouldn't call gimp_progress_set_value() when drawing a preview. 2) The function process_row does not use the last parameter i. How is that a problem? 3) Ok, this is the serious one: The whole blurred region is shifted 1 pixel down. To check this, create a new white image with a single black pixel in the middle, and blur it with radius=1. Go back and forth and you will see the 3x3 gray square shifting down. Again, how is that a problem? This example code is meant to illustrate some concepts of GIMP plug-in development, in particular how to add a preview to your plug-in window. It is not meant to perform any useful image manipulation. It would be nice though if someone could have a look at the tutorial and update the example code. The user interface looks somewhat outdated as the code originates back to gimp 2.0. We could probably improve the look and feel of third-party plug-ins if we made sure that the example code on developer.gimp.org serves as a good example. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
