Help with Rotating Images

Help with Rotating Images

Post by Abhyudaya Agrawa » Wed, 10 Jun 1998 04:00:00



I'm trying to write a program which takes an image as input and displays
it on the screen, along with 3 dials - one to rotate it vertically, one to
rotate it horizontally, one to magnify/shrink it. (Identical to the dials
found in the Open Inventor Examiner Viewer). I need to call my own
functions to rotate/modify the image, so inbuilt functions cannot do.

I'm programming in a unix environment from an SGI machine. I have access
to various libraries like OpenInventor and OpenGL, but I'm new to this
stuff and I don't know much about it. I looked through the Open Inventor
book and it allows you to add an Examiner Viewer, but it can only be used
for a scene graph created with Inventor and doesn't let you call your own
functions when the various dials are used.

Can anyone help me?

Thanks in advance,
Abhay

**********************************************************************
Abhay Agrawal                                                 Freshman
Computer Science + Math                     Carnegie Mellon University

"I'd prefer being hated for what I am than being loved for what I'm not"
    --Anonyomous, 1996.
**********************************************************************

 
 
 

Help with Rotating Images

Post by Tagore Smit » Fri, 03 Jul 1998 04:00:00


If it is not important to you to be able to save the image after
viewing, Inventor may be quite good for you. It is in fact not that hard
to derive a viewer class with your own callbacks attached to the
thumbwheels- see The Inventor Toolmaker by Josie Wernecke (I hope I
spelled that right).
   But you don't even need to do that- you could just write a small app
which pastes the input image onto a quad and uses sensors or
manipulators to do the rotations, zooms, etc. These can be inserted into
your scene graph. This will be much easier than using OpenGl directly.
But you should definitely read and understand most of The Inventor
Mentor before you start to code.
   Is it really necessary that you write this in 3D? If not, consider
using the ImageVision library, if it exists on the machines that you
have access to. Of course it would require learning a bit about Xt or
Xlib to handle the user interaction, but these are worthwhile things to
know, and if you are set on using thumbwheels you will have to know them
a little bit anyway.

                                         Tagore Smith


> I'm trying to write a program which takes an image as input and displays
> it on the screen, along with 3 dials - one to rotate it vertically, one to
> rotate it horizontally, one to magnify/shrink it. (Identical to the dials
> found in the Open Inventor Examiner Viewer). I need to call my own
> functions to rotate/modify the image, so inbuilt functions cannot do.

> I'm programming in a unix environment from an SGI machine. I have access
> to various libraries like OpenInventor and OpenGL, but I'm new to this
> stuff and I don't know much about it. I looked through the Open Inventor
> book and it allows you to add an Examiner Viewer, but it can only be used
> for a scene graph created with Inventor and doesn't let you call your own
> functions when the various dials are used.

> Can anyone help me?

> Thanks in advance,
> Abhay


 
 
 

1. Rotating the image blurs the image

I've wanted to rotate a few images lately (Image>Rotate) but the image
becomes noticeably less sharp after the rotation.

One of the current Challenge photos, ep-12 (restaurant), is a good
example. I had wanted to rotate it as part of my repair so that the
chimney was vertical. But the image was just too unsharpened after the
rotation to use it.

For comparison I've rotated the same image in Photoshop by the same
amount (I think I used 2 degrees) and there was no change in
sharpness.

Is this a shortcoming in PSP or is there some trick to using Rotate?

Thanks, Ember

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