It's common to enhance images before displaying them by applying the Unsharp
Mask filter to them. (Gimp and other image editors can be used for doing this.)

I've now added an example in my Gaussian blur GitHub repository that shows how
one can apply an Unsharp Mask filter to images with POV-Ray alone.

The attached image shows an example image where such a filter has been applied
with POV-Ray.

--
Tor Olav
http://subcube.com

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Attachments:
Download 'image_unsharp_mask.png' (746 KB)

Preview of image 'image_unsharp_mask.png'

"Tor Olav Kristensen" <tor### [at] TOBEREMOVEDgmailcom> wrote:
> It's common to enhance images before displaying them by applying the Unsharp
> Mask filter to them. (Gimp and other image editors can be used for doing this.)
>
> I've now added an example in my Gaussian blur GitHub repository that shows how
> one can apply an Unsharp Mask filter to images with POV-Ray alone.
>
> The attached image shows an example image where such a filter has been applied
> with POV-Ray.

Here's the original image.

The difference in sharpness can easiest be spotted by examining the "Mercury"
text on the outboard engine.

For the source code, see the file Image_Unsharp_Mask.pov in this repository:
https://github.com/t-o-k/POV-Ray-gaussian-blur

--
Tor Olav
http://subcube.com

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Attachments:
Download 'smallboat_800x600.png' (576 KB)

Preview of image 'smallboat_800x600.png'

"Tor Olav Kristensen" <tor### [at] TOBEREMOVEDgmailcom> wrote:
> I've now added an example in my Gaussian blur GitHub repository that shows how
> one can apply an Unsharp Mask filter to images with POV-Ray alone.

That's astounding! I may already have a use for this. I have a scene that uses a
bitmap image as a background and I noticed that using an image_map blurs the
image slightly (unless I'm doing something wrong). Maybe your unsharp mask will
help this scene.

Thank you for sharing this inspirational source code!

Regards,
Dave Blandston

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"Dave Blandston" <nomail@nomail> wrote:
> "Tor Olav Kristensen" <tor### [at] TOBEREMOVEDgmailcom> wrote:
> > I've now added an example in my Gaussian blur GitHub repository that shows how
> > one can apply an Unsharp Mask filter to images with POV-Ray alone.
>
> That's astounding! I may already have a use for this. I have a scene that uses a
> bitmap image as a background and I noticed that using an image_map blurs the
> image slightly (unless I'm doing something wrong). Maybe your unsharp mask will
> help this scene.
>
> Thank you for sharing this inspirational source code!

I'm glad to hear this Dave.

Don't hesitate to ask if there's anything you need me to explain about these
macros.

--
Tor Olav
http://subcube.com
https://github.com/t-o-k/

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"Tor Olav Kristensen" <tor### [at] TOBEREMOVEDgmailcom> wrote:
> Don't hesitate to ask if there's anything you need me to explain about these
> macros.

That's a very kind offer. My computer is out for repairs for the next week to
two so I'll have to wait until it's back to see if your macros will work with
the particular project I have in mind. The improvement on the boat picture is so
dramatic that I can't wait to give it a try! The specifics of the scene I'm
working on are that I'm using an image mapped to a plane as a background,
combined with some CSG objects in the foreground. POV blurs the background image
slightly. The CSG objects don't need any sharpening so I don't want to apply the
unsharp mask to the completed image but I'm hoping your macros can restore the
background image to its original sharpness during the rendering process.

Regards,
Dave Blandston

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