Re: [Gimp-developer] Gaussian blur: Silly question or buffer error?
The answer is given by the definition of 'terms':
terms = (row 4) ? row : 4;
In pratice, that means that
- with row4 the loop is
for (i = 0; i = row; i++) {
...
}
- with row=4 the loop is
for (i = 0; i = 4; i++) {
...
}
Alastair M. Robinson wrote:
Hi,
I may be missing something obvious here, but I'm trying to understand
the workings of the Gaussian Blur plugin, since I need to implement
something similar myself, and either there's something screwy here, or
there's something obvious I'm missing.
In gimp-2.4.4/plugins/common/gauss.c, the gauss_iir() function,
at line 960 we have four pointers initialised - two to the beginning of
their respective buffers, and two to one tuple before the end.
sp_p = src;
sp_m = src + (height - 1) * bytes;
vp = val_p;
vm = val_m + (height - 1) * bytes;
But then the inner loop does this:
for (b = 0; b bytes; b++)
{
vpptr = vp + b; vmptr = vm + b;
for (i = 0; i = terms; i++)
{
*vpptr += n_p[i] * sp_p[(-i * bytes) + b] - d_p[i] * vp[(-i *
bytes) + b];
*vmptr += n_m[i] * sp_m[(i * bytes) + b] - d_m[i] * vm[(i *
bytes) + b];
}
...
On the first run through, with b=0, the index [(-i * bytes) + b] will be
negative for all but the first iteration, yet it's used with the sp_p
and vp pointers, which point to the beginning of their buffers, thus
accessing memory outside the buffer. Or am I missing something here?
And while we're on the subject, can anyone point me to an explanation of
the maths behind this IIR approximation of the Gaussian filter? I
understand Gaussian blurring well enough to implement a
convolution-based version, but I want to implement a
local-contrast-stretch filter - basically a gentle large-radius
unsharp-mask, which would require unfeasibly large convolution matrices
to do it that way.
All the best,
--
Alastair M. Robinson
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[Gimp-developer] Merged Image not able to be drawn on...
More on the bug I am running into. It very well may be that this is not a bug and just a feature or whatever that I am running into, but it's not very well explained anywhere, seemingly. I have an image that I have worked on, had multiple layers, then when merged down, it cannot be drawn on directly, even though only one layer is shown and no error message pops up. 2.2 didn't seem to feature this, as I have done it countless times. Seems to be intermittent, but it's hard to figure out when I don't have much time to debug. More info...when I am saving the image as a jpeg, it shows the message about transparency...so is there a hidden layer or something that isn't allowing me to draw on...oh hell, I am running out of words. I can send out a screenshot of the issue. Didn't want to send it to the list and waste bandwidth. BTW, this is a compiled-from-source version of 2.4.4. ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Merged Image not able to be drawn on...
Brendan wrote: More on the bug I am running into. It very well may be that this is not a bug and just a feature or whatever that I am running into, but it's not very well explained anywhere, seemingly. I have an image that I have worked on, had multiple layers, then when merged down, it cannot be drawn on directly, even though only one layer is shown and no error message pops up. 2.2 didn't seem to feature this, as I have done it countless times. Seems to be intermittent, but it's hard to figure out when I don't have much time to debug. More info...when I am saving the image as a jpeg, it shows the message about transparency...so is there a hidden layer or something that isn't allowing me to draw on...oh hell, I am running out of words. I can send out a screenshot of the issue. Didn't want to send it to the list and waste bandwidth. BTW, this is a compiled-from-source version of 2.4.4. ___ I suspect that sending the XCF file, as suggested earlier by I don't remember who, might be the best way to start. That should contain everything, hidden or not, in your picture. Good luck, Jim ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Merged Image not able to be drawn on...
On Wednesday 13 February 2008, Jim Sabatke wrote: Brendan wrote: More on the bug I am running into. It very well may be that this is not a bug and just a feature or whatever that I am running into, but it's not very well explained anywhere, seemingly. I have an image that I have worked on, had multiple layers, then when merged down, it cannot be drawn on directly, even though only one layer is shown and no error message pops up. 2.2 didn't seem to feature this, as I have done it countless times. Seems to be intermittent, but it's hard to figure out when I don't have much time to debug. More info...when I am saving the image as a jpeg, it shows the message about transparency...so is there a hidden layer or something that isn't allowing me to draw on...oh hell, I am running out of words. I can send out a screenshot of the issue. Didn't want to send it to the list and waste bandwidth. BTW, this is a compiled-from-source version of 2.4.4. ___ I suspect that sending the XCF file, as suggested earlier by I don't remember who, might be the best way to start. That should contain everything, hidden or not, in your picture. Sadly, it's private work product that I can't release...If someone mailed me off-list, I'm sure I could find a way. ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Bug? Clone Tool after Merge Layers
On Mon, 2008-02-11 at 21:39 -0500, Brendan wrote: [...] Layer Mask gets squashed down with a Merge Visible Layers command. After that, I can't seem to get the Clone or Heal or really any drawing tool to work on the image. Unselected everything even. Make sure the background layer is selected in the layers dialogue. Liam -- Liam Quin - http://www.holoweb.net/~liam/ XML Activity Lead, W3C, http://www.w3.org/People/Quin/ Pictures from old books: http://fromoldbooks.org/ Ankh: irc.sorcery.net irc.gnome.org www.advogato.org ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Bug? Clone Tool after Merge Layers
Hi, On Wed, 2008-02-13 at 09:05 -0500, Liam R E Quin wrote: On Mon, 2008-02-11 at 21:39 -0500, Brendan wrote: [...] Layer Mask gets squashed down with a Merge Visible Layers command. After that, I can't seem to get the Clone or Heal or really any drawing tool to work on the image. Unselected everything even. Make sure the background layer is selected in the layers dialogue. That should happen automatically after Merge Visible Layers. Do you end up with no layer being selected? That would be a bug then. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] IWarp as a tool
Hi, On Wed, 2008-02-13 at 02:06 +0200, Tor Lillqvist wrote: Currently it allocates a big buffer for the deformation vectors, two doubles for each pixel in the image. This should probably be changed to either use tile-based storage, or use a scaled (when necessary) deformation vector array with some fixed maximum size. You should be able to use a tile-manager for this. A tile-manager can hold any number of bytes per pixel. There is one tool already that does something like this, the IScissors tool. It even does something particularily elegant in that it uses a validate_proc so that only the tiles that are actually needed by the tool are calculated. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
Re: [Gimp-developer] Merged Image not able to be drawn on...
Hi, On Wed, 2008-02-13 at 20:05 -0500, Brendan wrote: I have an image that I have worked on, had multiple layers, then when merged down, it cannot be drawn on directly, even though only one layer is shown and no error message pops up. The single layer that is shown, is it selected? There is most likely a channel in your image which is selected as the active drawable. Sven ___ Gimp-developer mailing list Gimp-developer@lists.XCF.Berkeley.EDU https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-developer
