Issue regarding Lanczos and Mitchell Filters

[*K*T*C*]

Hi,

I noticed some problem with the Lanczos and Mitchell filters. It looks to me like they might produce color values that are out of range and aren't rounded correctly. I uploaded some pictures to illustrate this behaviour (although it can be perceived on many photos, I thought I'd choose one of a pretty girl :lol:).

The bicubic version looks as expected, but the Lanczos and and Mitchell filtered versions show some more or less apparent artifacts at the saxophone and most apparently on this small silver plate attached to the lace holding the saxophone:

• Bicubic Filter
• Lanczos Filter
• Mitchell Filter

In case you want to reproduce it, here is the original image (careful, 1.4MB). It was scaled down to 480x640 and saved as a JPEG with quality setting 85 to produce the above images. Oh, and I am using cam2pc version 4.3.0.

Best,
Michael

[*K*T*C*]

Hey,
any comments? Did noone else encounter this problem? Or isn't it a problem at all and I am just too stupid? Please tell me...

Michael

[nabocorp]

Sorry, I did not have time to look at this. Will try this week-end!

Regards,
nabocorp

[nabocorp]

Fixed! This will be in 4.3.2.

Regards,
nabocorp

[*K*T*C*]

That was quick! Thanks.
Just out of curiosity, was it what is suspected?

Best,
Michael

[nabocorp]

Color values range from 0 to 255 for each channel (RGB). I was just putting values from 0 to 256 instead of 255. And 256 becomes 0. So when you should have an almost white pixel I could have (254, 256, 256) which becomes (254, 0, 0) which is a red pixel!

Hope you understand what I mean!

Regards,
nabocorp

[nabocorp]

BTW, for information for people who do not know. 0 to 255 for a channel is 256 possibilities. 256 can be coded on 8 bits (or 1 byte). As you have 3 channels, that's why we say that your camera outputs 3*8 = 24 bits per pixel images.

High-end cameras are able to produce 48 bits image: 16 bits per channel. In that case, color values can have 2^16 = 65536 different values ie. range from 0 to 65535.

nabocorp