Legacy ImageMagick Discussions Archive

One thing I am curious about but have had no time to experiment with is whether such "clamping" is better done in linear light or in perceptual spaces. Generally, upsampling (enlarging) through a perceptual space is better than linear light, at least when the filter has negative lobes. Whe...

This approach is reasonable and a bit reminiscent of what is done in the LBB component of the nohalo sampler (in the GEGL and VIPS FLOSS libraries; just google nohalo image sampler). ----- Instead of (min-d,max+d), what I would do is blend (lerp) the unclamped result with the clamped result. I would...

I find the "texturelessness" unnatural. I personally would tone down the anti-ringing (not eliminate it: just turn it down).
Otherwise, it's an interesting approach. Good job!
(My apologies for a very cursory evaluation. No time for more.)

Your set up definitely has a very particular "look".
Are you sure that all you do is use linear filtering with your modified weights?

Thank you for your answers Anthony and Alan. Note: All the evidence I've seen points to downsampling through linear light being generally better when using a linear resampling method (like most of IM's are). I have not tested this enough to be 100% sure, but close. (Unfortunately, I have little time...

I just remembered that because linear light spaces are, at least in principle, mapped to one another through an affine transformation, provided there is no clamping or other nonlinearity in the intermediate steps it should make no difference which one is used when using linear resampling. (Note that...

Anthony, many places, has stated that one good thing about resampling through Lab is that it has a luma/luminance channel. This, actually, makes a lot of sense. Now, it is fairly well established that downsampling (reducing the pixel size of an image, that is, "shrinking it" as in producin...

With line or pixel art, downsampling through Lab may actually be an excellent choice (untested: off the top of my head). Rationale: It has a luma channel, and if the line art is mostly made with dark lines, the "dark" bias that one gets going through perceptual may help keeping dark lines ...

It would be nice if someone took the time to do a comparison like http://www.imagemagick.org/discourse-server/viewtopic.php?f=22&t=21804 but downsampling line art instead of upsampling. (Tensor) Lanczos -filter Lanczos -resize , EWA Robidoux -distort Resize or the above mentioned EWA LanczosShar...

When dealing with line art, there is one good reason to use Lab (or L*a*b*): There is a luma/luminance channel. When downsampling, however, it is >>generally<< preferable to use linear light. A good way to get both a color space with a luma/luminance channel and linear light is resampling through XY...

P.S. RE: last comment:
This is what the boldface text in http://www.imagemagick.org/Usage/resize/#resize hints at.

Another good start: http://www.imagemagick.org/Usage/resize/#thin_lines . A bit more info RE: http://www.imagemagick.org/Usage/filter/nicolas/#downsample . With line art, the "downsample through linear light" diktat may or may not be relevant. Downsampling through Lab, which normally I wou...

If I understand correctly, what Steve wants to do is resize, mostly, line art (not pixel art, line art). My general recommendations for downsampling (linked above by Fred) consequently may or may not "hit the spot". Although I can make some educated guesses, this falls outside of what I ha...

\o/

The above RobidouxSharp comes from minimizing the worst case deviation from the original value when the original value is one of the two extremes (0 and 255 in typical 8 bit). An alternate way is to minimize the worst case deviation when the original value is the average of the largest and smallest...