Discuss digital image processing techniques and algorithms. We encourage its application to ImageMagick but you can discuss any software solutions here.
Basically what I'm doing is a gamma correct symmetrical cubic resampling with sigmoidal contrast adjustment and a high-pass filter afterwards to amplify some of the high frequency content. I think I want to use this filter mainly for downsampling.
Any suggestions or criticism is highly appreciated.
I definitely think I'm happy with this as a downsampling filter. So if this can be integrated into ImageMagick that would make me happy. I think I want it to be called bamsampler.
BAMscaler turns the eyes of the fly to rust.
It actually is not faithful tone wise elsewhere as well. By a lot.
And it is very blurry. And yet it has occasional significant halo, which often can be attributed to "color separation" combined, I would guess, with the Sobel.
Same with the backpack. P.S. I gave up on downloading your test image after half an hour of slow trickle. P.S. 2 The above had to do with the BAM which uses Cubic (really, Spline) to do the hard work. I'll try your latest.
The Kaiser scheme is tonally unfaithful when there is texture, like the previous scheme. (No surprise: sigmoidization appears to be almost always a bad idea when downsampling, despite what I stupidly suggested in the first pass of my "Recommendations".)
It also has an immense amount of halo given how sharp it is, it is quite jaggy, and the moire is horrible on the fly.
@Bryant:
The only high frequency components of your latest image are sharp interfaces between essentially flat colour areas, exactly the type of thing sigmoidization does well at.
Because the only "drift" is along boundaries, of course you don't see colour drift.
NicolasRobidoux wrote:@Bryant:
The only high frequency components of your latest image are sharp interfaces between essentially flat colour areas, exactly the type of thing sigmoidization does well at.
Because the only "drift" is along boundaries, of course you don't see colour drift.
Seems to produce some significant moire in the eyes, not sure how to combat that currently; it handles the CG images rather well. I suspect the moire would only be worse at non-integer downsamplings.
The "standard" test I and others use with the fly is resizing to exactly 403x600. Then, you can compare to the million versions of this test I have in the Forums. This is not an integer ratio by any means.
NicolasRobidoux wrote:The "standard" test I and others use with the fly is resizing to exactly 403x600. Then, you can compare to the million versions of this test I have in the Forums. This is not an integer ratio by any means.
