On 13/11/2023 08:32, Dave Blandston wrote:
> Howdy Folks,
> 
> I'm experimenting with the blur effect commonly seen bordering social media
> images. I contemplated writing the code to perform a Gaussian blur which seemed
> simple enough until I got to the part about edge handling. Well, sure enough Tor
> Olav Kristensen has already done the hard work and made a Gaussian blur include
> file for POV so I'm trying it out. As I anticipated, the level of mathematical
> and algorithmic sophistication in this file is far beyond my humble abilities so
> I'm unable to modify it to get the results I hoped for. Fortunately this is just
> a for-fun project so I'm giving up pretty easily. However, I'm curious if anyone
> has experience using this file and knows what's going on in the attached image.
> The top picture shows desired results that I made with a paint program. The
> middle picture shows the POV version. The green background seems to show through
> around the edges. I changed all the filter and transmit values to 0 in Tor's
> file but the background still shows through. The bottom picture just shows the
> POV version again with a background of White * -1, which gave the best results
> but still not quite what I was looking for.
> 
> Have a great day everyone!
> 
> Kind regards,
> Dave Blandston
> 

Hello.

I don't think you quite understand how TOK did it (granted, it's not
easy). In fact, the key is in the SelectRectangleFn function and in the
texture_map.

For the function, the return value (0 or 1) is juste a value which will
be used in the texture_map.

The texture_map say that "0" is mapped to ImagePigment and for "1"
mapped to BlurredImagePigmentGy.


Having said that, I modified TOK's "Blur_Image_Region.pov" file :


#declare SelectRectangleFn = function {
	1
	*select(x - 0.25*Width, 0, 1)
	*select(x - 0.75*Width, 1, 0)
	*select(y - 0.00*Height, 0, 1)
	*select(y - 1.00*Height, 1, 0)
	};

In x direction 0 to 200 and 600 to 800
In y direction 0 to 600.

and now it's time to modify the "texture_map"

texture_map {
//	[ 0.0 pigment { color Yellow } ]
	[ 0.0 BlurredImagePigmentGy ]
	[ 1.0 ImagePigment ]
	}


Which gives the attached image.

Hope that help.


-- 
Kurtz le pirate
Compagnie de la Banquise

Post a reply to this message

Attachments:
Download 'blur_image_region-2.jpg' (30 KB)

Preview of image 'blur_image_region-2.jpg'