resizing algorithms
Posted: Fri Aug 27, 2010 10:23 am
Good morning all.
I hope this is not a spurious question but I'm highly amateurish when it comes to taking / editing pictures... and I was curious about peoples' opinions regarding the various algorithms available when resizing/resampling.
My current task is a simple reduction of a 600 width photo down to 534. I have chosen to "Keep Ratio" and "Resample".
I know it's something of a subjective topic but I personally found Lanczos to deliver the best image reduction. I judged this mainly on the fact that the other algorithms seemed to lose sharpness, and Lanczos seemed to be closest to the original image's appearance.
I did do a bit of research before I posted here... and I generally saw bilinear and bicubic bandied around as well-known / recognised algorithms. Bilinear could be considered better for enlarging, because of its smoothing effect. Bicubic could be considered better for reduction, because of its sharpening effect.
I looked for Bicubic as an option in XnView and couldn't find it but then found a post stating that Mitchell was Bicubic. However, as already stated, Lanczos still seemed to provide greater levels of sharpening (on reduction) than Mitchell.
Am I doing something wrong?
What do people think?
Additionally, it also occurred to me that the 'performance' of an algorithm might be related to how large a resizing is being undertaken I.e. if you're dropping resolution by 2000px, perhaps one algorithm is 'better' than another?
Finally, it would be very interesting & instructive to hear opinion on the 9 algorithms available in XnView and when you use one, as compared to another.
Many thanks for any replies.
Gary
I hope this is not a spurious question but I'm highly amateurish when it comes to taking / editing pictures... and I was curious about peoples' opinions regarding the various algorithms available when resizing/resampling.
My current task is a simple reduction of a 600 width photo down to 534. I have chosen to "Keep Ratio" and "Resample".
I know it's something of a subjective topic but I personally found Lanczos to deliver the best image reduction. I judged this mainly on the fact that the other algorithms seemed to lose sharpness, and Lanczos seemed to be closest to the original image's appearance.
I did do a bit of research before I posted here... and I generally saw bilinear and bicubic bandied around as well-known / recognised algorithms. Bilinear could be considered better for enlarging, because of its smoothing effect. Bicubic could be considered better for reduction, because of its sharpening effect.
I looked for Bicubic as an option in XnView and couldn't find it but then found a post stating that Mitchell was Bicubic. However, as already stated, Lanczos still seemed to provide greater levels of sharpening (on reduction) than Mitchell.
Am I doing something wrong?
What do people think?
Additionally, it also occurred to me that the 'performance' of an algorithm might be related to how large a resizing is being undertaken I.e. if you're dropping resolution by 2000px, perhaps one algorithm is 'better' than another?
Finally, it would be very interesting & instructive to hear opinion on the 9 algorithms available in XnView and when you use one, as compared to another.
Many thanks for any replies.
Gary