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squaring up an image

Message-ID:<URd8l.3471$Es4.1300@nwrddc01.gnilink.net>
Subject:

squaring up an image

Date:Mon, 5 Jan 2009 03:01:24 +0100


Hello,

I seem to repeatedly run into a situation where I have a .jpg photo that I 
took of a rectangular object, but the rectangular object in the image is not 
truly rectangular.  I would like to know a good method for "squaring up" the 
image in this situation.

I have tried using the Perspective function in GIMP.  This seems to be 
useful if the perspective distortion is consistent.  But the situation I 
seem to run into often is that the left half of the image, say,  is pretty 
rectangular, but in the right half two of the sides may converge slightly, 
for example.  Or one side may curve slightly for some reason.  Using the 
Perpective tool in this situation may improve the right half, but throws the 
left half out of alignment.

I was thinking that it would be nice if I could define a path made up of 
points along the image that I want to be rectangular, and then select a 
command somewhere that would stretch and/or compress the image in the 
appropriate places.  My sense is that such a command does not exist (I would 
love it if someone would prove me wrong about this).  So I am searching for 
an alternative approach.

All advice is appreciated!

Thanks,
Joe

Message-ID:<9572ae9c-f778-4226-a408-3ec4f1bb75c9@o4g2000pra.googlegroups.com>
Subject:

Re: squaring up an image

Date:Mon, 5 Jan 2009 05:51:19 +0100


On Jan 5, 1:01=A0pm, "JoeM" <joenopsam4...@gmail.com> wrote:
> Hello,
>
> I seem to repeatedly run into a situation where I have a .jpg photo that =
I
> took of a rectangular object, but the rectangular object in the image is =
not
> truly rectangular. =A0I would like to know a good method for "squaring up=
" the
> image in this situation.
>
> I have tried using the Perspective function in GIMP. =A0This seems to be
> useful if the perspective distortion is consistent. =A0But the situation =
I
> seem to run into often is that the left half of the image, say, =A0is pre=
tty
> rectangular, but in the right half two of the sides may converge slightly=
,
> for example. =A0Or one side may curve slightly for some reason. =A0Using =
the
> Perpective tool in this situation may improve the right half, but throws =
the
> left half out of alignment.
>
> I was thinking that it would be nice if I could define a path made up of
> points along the image that I want to be rectangular, and then select a
> command somewhere that would stretch and/or compress the image in the
> appropriate places. =A0My sense is that such a command does not exist (I =
would
> love it if someone would prove me wrong about this). =A0So I am searching=
 for
> an alternative approach.




Not sure how you get a camera image that is not rectangular,  but I
think you need the "Rotate tool"

Use corrective and preview Image+Grid and rotate till it lines up with
something that is meant to be vertical or horozontial



Owen

Message-ID:<4961ba08$0$1432$426a74cc@news.free.fr>
Subject:

Re: squaring up an image

Date:Mon, 5 Jan 2009 08:43:03 +0100


JoeM wrote:
> Hello,
> 
> I seem to repeatedly run into a situation where I have a .jpg photo that 
> I took of a rectangular object, but the rectangular object in the image 
> is not truly rectangular.  I would like to know a good method for 
> "squaring up" the image in this situation.
> 
> I have tried using the Perspective function in GIMP.  This seems to be 
> useful if the perspective distortion is consistent.  But the situation I 
> seem to run into often is that the left half of the image, say,  is 
> pretty rectangular, but in the right half two of the sides may converge 
> slightly, for example.  Or one side may curve slightly for some reason.  
> Using the Perpective tool in this situation may improve the right half, 
> but throws the left half out of alignment.
> 
> I was thinking that it would be nice if I could define a path made up of 
> points along the image that I want to be rectangular, and then select a 
> command somewhere that would stretch and/or compress the image in the 
> appropriate places.  My sense is that such a command does not exist (I 
> would love it if someone would prove me wrong about this).  So I am 
> searching for an alternative approach.

Your image is likely suffering from distortions introduced by the lens. 
This is better fixed by a specialized tool that has distortion data for 
the camera (or the lens, for DSLRs) before applying the perspective 
tool. The same tool will also fix chromatic aberrations.

-- 
Bertrand

Message-ID:<URd8l.3471$Es4.1300@nwrddc01.gnilink.net>
Subject:

squaring up an image

Date:Mon, 5 Jan 2009 03:01:24 +0100


Hello,

I seem to repeatedly run into a situation where I have a .jpg photo that I 
took of a rectangular object, but the rectangular object in the image is not 
truly rectangular.  I would like to know a good method for "squaring up" the 
image in this situation.

I have tried using the Perspective function in GIMP.  This seems to be 
useful if the perspective distortion is consistent.  But the situation I 
seem to run into often is that the left half of the image, say,  is pretty 
rectangular, but in the right half two of the sides may converge slightly, 
for example.  Or one side may curve slightly for some reason.  Using the 
Perpective tool in this situation may improve the right half, but throws the 
left half out of alignment.

I was thinking that it would be nice if I could define a path made up of 
points along the image that I want to be rectangular, and then select a 
command somewhere that would stretch and/or compress the image in the 
appropriate places.  My sense is that such a command does not exist (I would 
love it if someone would prove me wrong about this).  So I am searching for 
an alternative approach.

All advice is appreciated!

Thanks,
Joe

Message-ID:<9572ae9c-f778-4226-a408-3ec4f1bb75c9@o4g2000pra.googlegroups.com>
Subject:

Re: squaring up an image

Date:Mon, 5 Jan 2009 05:51:19 +0100


On Jan 5, 1:01=A0pm, "JoeM" <joenopsam4...@gmail.com> wrote:
> Hello,
>
> I seem to repeatedly run into a situation where I have a .jpg photo that =
I
> took of a rectangular object, but the rectangular object in the image is =
not
> truly rectangular. =A0I would like to know a good method for "squaring up=
" the
> image in this situation.
>
> I have tried using the Perspective function in GIMP. =A0This seems to be
> useful if the perspective distortion is consistent. =A0But the situation =
I
> seem to run into often is that the left half of the image, say, =A0is pre=
tty
> rectangular, but in the right half two of the sides may converge slightly=
,
> for example. =A0Or one side may curve slightly for some reason. =A0Using =
the
> Perpective tool in this situation may improve the right half, but throws =
the
> left half out of alignment.
>
> I was thinking that it would be nice if I could define a path made up of
> points along the image that I want to be rectangular, and then select a
> command somewhere that would stretch and/or compress the image in the
> appropriate places. =A0My sense is that such a command does not exist (I =
would
> love it if someone would prove me wrong about this). =A0So I am searching=
 for
> an alternative approach.




Not sure how you get a camera image that is not rectangular,  but I
think you need the "Rotate tool"

Use corrective and preview Image+Grid and rotate till it lines up with
something that is meant to be vertical or horozontial



Owen

Message-ID:<4961ba08$0$1432$426a74cc@news.free.fr>
Subject:

Re: squaring up an image

Date:Mon, 5 Jan 2009 08:43:03 +0100


JoeM wrote:
> Hello,
> 
> I seem to repeatedly run into a situation where I have a .jpg photo that 
> I took of a rectangular object, but the rectangular object in the image 
> is not truly rectangular.  I would like to know a good method for 
> "squaring up" the image in this situation.
> 
> I have tried using the Perspective function in GIMP.  This seems to be 
> useful if the perspective distortion is consistent.  But the situation I 
> seem to run into often is that the left half of the image, say,  is 
> pretty rectangular, but in the right half two of the sides may converge 
> slightly, for example.  Or one side may curve slightly for some reason.  
> Using the Perpective tool in this situation may improve the right half, 
> but throws the left half out of alignment.
> 
> I was thinking that it would be nice if I could define a path made up of 
> points along the image that I want to be rectangular, and then select a 
> command somewhere that would stretch and/or compress the image in the 
> appropriate places.  My sense is that such a command does not exist (I 
> would love it if someone would prove me wrong about this).  So I am 
> searching for an alternative approach.

Your image is likely suffering from distortions introduced by the lens. 
This is better fixed by a specialized tool that has distortion data for 
the camera (or the lens, for DSLRs) before applying the perspective 
tool. The same tool will also fix chromatic aberrations.

-- 
Bertrand

Message-ID:<URd8l.3471$Es4.1300@nwrddc01.gnilink.net>
Subject:

squaring up an image

Date:Mon, 5 Jan 2009 03:01:24 +0100


Hello,

I seem to repeatedly run into a situation where I have a .jpg photo that I 
took of a rectangular object, but the rectangular object in the image is not 
truly rectangular.  I would like to know a good method for "squaring up" the 
image in this situation.

I have tried using the Perspective function in GIMP.  This seems to be 
useful if the perspective distortion is consistent.  But the situation I 
seem to run into often is that the left half of the image, say,  is pretty 
rectangular, but in the right half two of the sides may converge slightly, 
for example.  Or one side may curve slightly for some reason.  Using the 
Perpective tool in this situation may improve the right half, but throws the 
left half out of alignment.

I was thinking that it would be nice if I could define a path made up of 
points along the image that I want to be rectangular, and then select a 
command somewhere that would stretch and/or compress the image in the 
appropriate places.  My sense is that such a command does not exist (I would 
love it if someone would prove me wrong about this).  So I am searching for 
an alternative approach.

All advice is appreciated!

Thanks,
Joe

Message-ID:<9572ae9c-f778-4226-a408-3ec4f1bb75c9@o4g2000pra.googlegroups.com>
Subject:

Re: squaring up an image

Date:Mon, 5 Jan 2009 05:51:19 +0100


On Jan 5, 1:01=A0pm, "JoeM" <joenopsam4...@gmail.com> wrote:
> Hello,
>
> I seem to repeatedly run into a situation where I have a .jpg photo that =
I
> took of a rectangular object, but the rectangular object in the image is =
not
> truly rectangular. =A0I would like to know a good method for "squaring up=
" the
> image in this situation.
>
> I have tried using the Perspective function in GIMP. =A0This seems to be
> useful if the perspective distortion is consistent. =A0But the situation =
I
> seem to run into often is that the left half of the image, say, =A0is pre=
tty
> rectangular, but in the right half two of the sides may converge slightly=
,
> for example. =A0Or one side may curve slightly for some reason. =A0Using =
the
> Perpective tool in this situation may improve the right half, but throws =
the
> left half out of alignment.
>
> I was thinking that it would be nice if I could define a path made up of
> points along the image that I want to be rectangular, and then select a
> command somewhere that would stretch and/or compress the image in the
> appropriate places. =A0My sense is that such a command does not exist (I =
would
> love it if someone would prove me wrong about this). =A0So I am searching=
 for
> an alternative approach.




Not sure how you get a camera image that is not rectangular,  but I
think you need the "Rotate tool"

Use corrective and preview Image+Grid and rotate till it lines up with
something that is meant to be vertical or horozontial



Owen

Message-ID:<4961ba08$0$1432$426a74cc@news.free.fr>
Subject:

Re: squaring up an image

Date:Mon, 5 Jan 2009 08:43:03 +0100


JoeM wrote:
> Hello,
> 
> I seem to repeatedly run into a situation where I have a .jpg photo that 
> I took of a rectangular object, but the rectangular object in the image 
> is not truly rectangular.  I would like to know a good method for 
> "squaring up" the image in this situation.
> 
> I have tried using the Perspective function in GIMP.  This seems to be 
> useful if the perspective distortion is consistent.  But the situation I 
> seem to run into often is that the left half of the image, say,  is 
> pretty rectangular, but in the right half two of the sides may converge 
> slightly, for example.  Or one side may curve slightly for some reason.  
> Using the Perpective tool in this situation may improve the right half, 
> but throws the left half out of alignment.
> 
> I was thinking that it would be nice if I could define a path made up of 
> points along the image that I want to be rectangular, and then select a 
> command somewhere that would stretch and/or compress the image in the 
> appropriate places.  My sense is that such a command does not exist (I 
> would love it if someone would prove me wrong about this).  So I am 
> searching for an alternative approach.

Your image is likely suffering from distortions introduced by the lens. 
This is better fixed by a specialized tool that has distortion data for 
the camera (or the lens, for DSLRs) before applying the perspective 
tool. The same tool will also fix chromatic aberrations.

-- 
Bertrand