Re: [Gimp-developer] transformation drift [was: preview window does not work]
Hi, On Fri, 2007-03-09 at 09:07 +0100, Sven Neumann wrote: If you have a look at it now, be warned that there's a bug in the pixel-surround routines which I introduced two days ago. I am aware of the bug and I will either fix it over the next days or revert some optimizations. So please don't wonder about artefacts at the bottom of the source area, these are due to this bug. Just FYI: That problem should be fixed now. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] transformation drift [was: preview window does not work]
On Sat, 10 Mar 2007 21:24:13 +0100, Sven Neumann [EMAIL PROTECTED] wrote: Hi, On Fri, 2007-03-09 at 09:07 +0100, Sven Neumann wrote: If you have a look at it now, be warned that there's a bug in the pixel-surround routines which I introduced two days ago. I am aware of the bug and I will either fix it over the next days or revert some optimizations. So please don't wonder about artefacts at the bottom of the source area, these are due to this bug. Just FYI: That problem should be fixed now. Sven thx for the update. gg ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] transformation drift [was: preview window does not work]
Hi, On Thu, 2007-03-08 at 09:45 +0100, [EMAIL PROTECTED] wrote: I have limitted time right now but I'll try to have a look in the next few days, though I dont follow your logic. If you have a look at it now, be warned that there's a bug in the pixel-surround routines which I introduced two days ago. I am aware of the bug and I will either fix it over the next days or revert some optimizations. So please don't wonder about artefacts at the bottom of the source area, these are due to this bug. The reason this is optimised like this is because there is NO NEED for any fancy techniques since it's a one-to-one mapping. Is it really always a one-to-one mapping? I might be wrong but this seems to be dependant on the choice of the center of rotation and I am not sure if correctly check for this. I did start to look into this a while back but ran out of time. One source of error I noted was that the code splits all transforms into an origin and offset coordinates for just about all operations. Many of these are done with the origin at the image centre. This means two truncations , two rounding errors. Sounds like we should investigate this further. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] transformation drift [was: preview window does not work]
On 3/8/07, Sven Neumann [EMAIL PROTECTED] wrote: Hi, If you rotate by exactly 90 degrees, this is always done with INTERPOLATION_NONE, no matter what you select in the tool options. Perhaps this is the culprit? An offset seems unavoidable if the transformation is performed without interpolation. So perhaps all we need to do is to remove this optimization (which is supposed to speed up rotations by multiple of 90 degrees)? BTW, do you think the rotation centre should be snapped to 0.5 pixel increments when interpolation is NONE? It doesn't make sense to have any more precision at that point (and can introduce glitches -- for instance, try floating a rectangular region, then dragging the rotation centre to the top left as precisely as you can, setting it to rotate 90 degrees, and performing the rotation... -- compared to inputting the coordinates of the top left yourself and then performing the 90 degree rotation. In the first case, even fractional imprecision means the result is not even in the right place.) Anyway, in the case of a 90 degree rotation, it seems unlikely that the user would want it misaligned with the pixels -- in which case no interpolation is needed and the result should be exactly right. Simple test case that uniformly fails, currently: * Select a rectangular region of the picture. * Float it * Rotate it. Set the rotation centre to the exact top left (by first positioning the centre near it, then editing the coordinates in the rotation dialog to make them exact). Set the angle to 90 degrees and the interpolation to NONE. Supersampling option appears to have no effect in this case. * The result may be offset by 1 pixel in X and/or Y axis; It is also missing one line of pixels (which line is omitted varies.) ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] transformation drift [was: preview window does not work]
On Thu, 08 Mar 2007 11:54:25 +0100, David Gowers [EMAIL PROTECTED] wrote: On 3/8/07, Sven Neumann [EMAIL PROTECTED] wrote: Hi, If you rotate by exactly 90 degrees, this is always done with INTERPOLATION_NONE, no matter what you select in the tool options. Perhaps this is the culprit? An offset seems unavoidable if the transformation is performed without interpolation. So perhaps all we need to do is to remove this optimization (which is supposed to speed up rotations by multiple of 90 degrees)? BTW, do you think the rotation centre should be snapped to 0.5 pixel increments when interpolation is NONE? It doesn't make sense to have any more precision at that point (and can introduce glitches -- for instance, try floating a rectangular region, then dragging the rotation centre to the top left as precisely as you can, setting it to rotate 90 degrees, and performing the rotation... -- compared to inputting the coordinates of the top left yourself and then performing the 90 degree rotation. In the first case, even fractional imprecision means the result is not even in the right place.) Anyway, in the case of a 90 degree rotation, it seems unlikely that the user would want it misaligned with the pixels -- in which case no interpolation is needed and the result should be exactly right. Simple test case that uniformly fails, currently: * Select a rectangular region of the picture. * Float it * Rotate it. Set the rotation centre to the exact top left (by first positioning the centre near it, then editing the coordinates in the rotation dialog to make them exact). Set the angle to 90 degrees and the interpolation to NONE. Supersampling option appears to have no effect in this case. * The result may be offset by 1 pixel in X and/or Y axis; It is also missing one line of pixels (which line is omitted varies.) I think you can achieve the same results without floating. Just try a rotate. gg ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
[Gimp-developer] transformation drift [was: preview window does not work]
Hi, If you rotate by exactly 90 degrees, this is always done with INTERPOLATION_NONE, no matter what you select in the tool options. Perhaps this is the culprit? An offset seems unavoidable if the transformation is performed without interpolation. So perhaps all we need to do is to remove this optimization (which is supposed to speed up rotations by multiple of 90 degrees)? Peter, can you try to remove that code in app/core/gimp-transform-region.c (line 208 and 209) and check if that fixes your test case? Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
