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How do I change the perspective of an image?

Sep 28, 2012, 18:33
Post: #1
How do I change the perspective of an image?
Hi, I'm new to GIMP and need help. I have a photo of a coffee table that's on an angle. I want to rotate this table so it looks like you're standing in front of it and seeing the front. The problem is the Rotate, Perspective, and Map Object tools don't seem to be able to do it. I also tried a plug-in called EZ Perspective, but that also doesn't seem to work.

At this point, I'm guessing you can't change the perspective of an image (up, down, left, right) because it's flat and not 3D, and no program knows what the other sides would look like. Is that correct, or can I do what I want and just don't know how, yet?

Here's a photo of the image:    
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Sep 28, 2012, 22:17
Post: #2
RE: How do I change the perspective of an image?
That's correct, in the general case, changing the perspective involves showing new things so you cannot do it with basic tools. In the present case, though, nothing new appears, beside the slight change of shape the big difference is that a side and a leg disappear, and this is easy to do.

Now answering your questions on
https://Gimp-Forum.net
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Sep 29, 2012, 02:29
Post: #3
RE: How do I change the perspective of an image?
(Sep 28, 2012 22:17)ofnuts Wrote:  That's correct, in the general case, changing the perspective involves showing new things so you cannot do it with basic tools. In the present case, though, nothing new appears, beside the slight change of shape the big difference is that a side and a leg disappear, and this is easy to do.

But GIMP is the world's most powerful free image-manipulation software, yet it can't do it? Is there a software that can do it, and if so, what's its name?

Would you mind editing my photo like I want so I can see if it's possible and explaining how you did it? It should be easy for a GIMP guru like you, right?

I love GIMP. I've been using it just 1 day, and I already have created a professional realistic-looking furnished room. And I learned all through just toying with it. My only gripe is the manual is terrible and assumes the reader knows too much, and the Perspective Tool should be called the Distort Tool.
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Sep 29, 2012, 10:11 (This post was last modified: Sep 29, 2012 10:12 by rich2005.)
Post: #4
RE: How do I change the perspective of an image?
You sound awfully like a troll. Benefit of the doubt.
Quote:But GIMP is the world's most powerful free image-manipulation software, yet it can't do it?
No, it can't see the other side of a brick wall either, but then neither can PS, Corel or other 2d image editors.

Quote:Is there a software that can do it, and if so, what's its name?
You image looks very much like a blender model, so I would go for that.
http://www.blender.org/
This is not blender but it is a table.
[Image: g19EQ.jpg]

Quote:Would you mind editing my photo like I want so I can see if it's possible and explaining how you did it? It should be easy for a GIMP guru like you, right?
I love GIMP. I've been using it just 1 day, and I already have created a professional realistic-looking furnished room. And I learned all through just toying with it...

That is the right approach, keep on trying.

** https://www.gimp-forum.net/ now answering questions**
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Sep 29, 2012, 21:04
Post: #5
RE: How do I change the perspective of an image?
(Sep 29, 2012 10:11)rich2005 Wrote:  You sound awfully like a troll.

No idea why you'd think that. Definitely not a troll. I'm a guy looking to get the most out of GIMP.

I thought GIMP was a 2D and 3D editor? It's just 2D?

That table I uploaded is not a 3D model. It's a 2D photo, and I'm guessing Blender or any other program can't interpret perspective of 2D images because no algorithm is intelligent enough? Sure, you can rotate a 3D model because it has all four sides, but not 2D. That's just a guess, but is it true?

And a couple separate GIMP questions:
How do you select an object in an image that's been saved? I want the dotted-line selection tool to wrap around the object the same way it does when you paste an object into the image for the first time. All I can do is use the Rectangular Selection Tool, but that doesn't perfectly wrap around the object so I can manipulate it again and it leaves white pixels.

Let's suppose I had a green box with a white boarder and a smaller white box inside the bigger green box. Then I click By Color, click the color I want to make transparent in the image, then click Layer > Transparency > Alpha Channel (I don't remember the exact option names). But I want to know how to select a color to make transparent but then deselect other areas with that same color I want to keep. I hope that's clear.
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Sep 30, 2012, 08:50 (This post was last modified: Sep 30, 2012 08:53 by rich2005.)
Post: #6
RE: How do I change the perspective of an image?
Quote:I thought GIMP was a 2D and 3D editor? It's just 2D?

Where did you get that idea? Gimp is a raster editor, your image is a series of pixels. Edit the image and you change the order of the pixels and that is all.

Quote:That table I uploaded is not a 3D model. It's a 2D photo... Sure, you can rotate a 3D model because it has all four sides, but not 2D. That's just a guess, but is it true?

Just looked like the sort of image you get rendering a 3D model and you asked for suggestions. Correct you are not able to rotate 2D to see the other side.

Quote:And a couple separate GIMP questions:
How do you select an object in an image that's been saved?

All sorts of ways to make a selection. Have a look at the link under Ofnuts sig
http://gimpforums.com/thread-efficient-a...selections
Also this is a video I made some time ago, it is in Gimp 2.6 but the tools have not changed in 2.8. It demonstrates the basics.
http://www.youtube.com/watch?v=aUHEI-bVSPo

Quote:Let's suppose I had a green box with a white boarder and a smaller white box inside the bigger green box. Then I click By Color, click the color I want to make transparent in the image, then click Layer > Transparency > Alpha Channel (I don't remember the exact option names). But I want to know how to select a color to make transparent but then deselect other areas with that same color I want to keep. I hope that's clear.

Also several ways but for 'Color-to-Alpha' & I'm not too sure what you are using, you could do it in stages like this.
[Image: VgTDE.jpg]
Basically adding/subtracting from selections, see above.
Mistake in that image, I circled the paintbrush instead of the rectangular select tool.

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Sep 30, 2012, 22:01 (This post was last modified: Sep 30, 2012 22:11 by vipejc.)
Post: #7
RE: How do I change the perspective of an image?
(Sep 30, 2012 08:50)rich2005 Wrote:  Where did you get that idea? Gimp is a raster editor, your image is a series of pixels. Edit the image and you change the order of the pixels and that is all.

Quote:I just assumed that because GIMP is the most powerful image manipulation program, it could work with 3D models. Thanks for clearing this up. That makes perfect sense.

Just looked like the sort of image you get rendering a 3D model and you asked for suggestions. Correct you are not able to rotate 2D to see the other side.

Quote:It really does look like a 3D model from that perspective. Fooled ya. LOL Thanks for clearing this up.

Quote:Thanks for that great video on learning how to use GIMP's selection tools. You've increased my knowledge on a key tool and taught me how to make the right selections. I've watched your video a few times and will watch it a few more. I'm a visual learner, so it's easy to follow.


Quote:Just one last thing, in your screenshot tutorial, the last step looks like it shows a green boarder around the green box; I want that boarder white. I still don't know how to use the By Color > Transparency options to select a color to make transparent and then deselect other areas of the image with that same color. The problem is GIMP will make all of that color transparent, and it's hard to repair those areas of the image using the paintbrush. I can do it, but I'd rather those pixels not be removed to begin with.
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