Making perspective surfaces flat

If you take a screenshot of a surface, it's often distorted by perspective. If you cut it out in PSP (or whatever) you get a four-sided, irregular shape. Question is: how do I make it look flat? Is there a way to stretch that into a square or rectangle that won't cost me money? Like a little freeware/shareware utility?

I'm not sure if I understand the question, but why not simply make sure, before taking the screenshot, that your camera angle is perpendicular to the surface?

There are functions like Distort, Skew, and Perspective in image editors which will do what you need for flat surfaces. It's also useful for extracting areas from RL images to use as textures. I'm not familiar with any free editors. Paintshop Pro is well worth the money though.

Cubey, if you work with Photoshop, it has a few filters and transformation tools that you can use to compensate for the distortion. I use the the "Perspective" and "Distort" transforms most often for this issue. The Liquify filter also has some features/settings that can help. I also know there is a third party plug-in for PS that does all the perspective adjusts automatically, but it costs $$. PSP must have some similar tools by now (V9.0). GIMP, I would imagine has at least one or more of these transform tools.

I only use PS, so I can't be of any more assistance to you for PSP and GIMP. Perhapse someone else can offer some guidance with these applications.

I think there is a function called "transform" in Photoshop but I have not messed with it much. It still won't look right though. I would suggest eliminating the problem when you take the screenshot buy first finding the center or exact middle of what you want to take a picture of. The more precice the better. Rezz a cube and place it in the exact middle and shrink it down some so it is relatively small compared to the surface you want. Drag-copy the cube away from the surface and maybe a meter from the original cube.

What you should have are two cubes (colored to be easily seen against the background if needed) hovering above the surface you want in the center, one near the surface the other a meter or two out. Now align your camera above the surface where you can see both cubes then move your camers around until one cube is exactly in line with the other and you only see the surface of one cube. This will have your camera looking directly at the center of the surface eliminating any perspective angles.

Cubey: Upgrade to Photoshop 8 or 9, man!

8 introduced a very slick perspective correction tool. It takes about 10 seconds to tell it where the outline of the image is, then in one click, boom, you have a nice, well-aligned image!

See example \/

It's unfortunatly not useful for some types of perspective correction... you can't really un-curve an image if its wrapped around a round shape, for example. I know of other programs that can, but PS can't (Yet! Muahahaha!)

If you're open to using new tools, I would suggest TextureMaker. You can download a trial version there.

Texturemaker has a neat tool call the Textractor which allows the user to do a crop on an image with a perspective tool... results attached below speak for themselves how well it works. 2 minutes of playi9ng to do this image.

Texturemaker does all kinds of fun texture stuff... definately worth checking out.

-Ghoti

I'm not actually capturing the texture on the flat surface. It's for creating shadow textures: I'm capturing the silhouettes of the objects between the light and the object surface where the shadow will be. Then I correct the perspective and put it on the suface.

Thanks, Ghoti. I'll check that out.

Photoshop has much more potential to fix this problem then Texturemaker.. tried it out.. seems cool.. cant pull myself away from all my versions of photoshop

i think this is what your looking for.

Tutorial - Adding realistic shadow inside SL

Use the tool that works best for you. I like the ease with which TextureMaker does this. I'm a Photoshop/Illustrator junkie (certified A.C.E. Photoshop 7 and Illustrator 10.. never bothered to renew) so its not like I'm saying don't use Photoshop. TextureMaker just seems to do it easier.

-Ghoti

if you need a plugin to compensate distortion on digital pictures, i suggest you the FREE DCE plugin for PS. Usually digital camera have a lens distortion if you take the shot too close.

http://photoshop.pluginsworld.com/plugin.php?editor=adobe&software=photoshop&plugin=264

there is lots of other kind of plugins to browse there also.

have fun!