shakedown.social is one of the many independent Mastodon servers you can use to participate in the fediverse.
A community for live music fans with roots in the jam scene. Shakedown Social is run by a team of volunteers (led by @clifff and @sethadam1) and funded by donations.

Administered by:

Server stats:

270
active users

#Imaging

2 posts1 participant0 posts today

Since the #PNG spec is getting some updates, I was thinking... you know what would be sick? Baking classic #lossy compression right into PNG.

I don't mean #JPEG or anything like that. Not even the #LossyPNG scheme I enjoy using where I reduce the number of colors to reduce the entropy. That wouldn't need any changes to the spec.

I'm thinking #Amiga HAM modes! Instant 3:1 (well, 2.4:1) lossy compression with (hopefully) minimal artifacting. That would be SICK!

Makes me want to throw together a Python script or something to read PNG files, apply the HAM "compression," and then see how the output looks. It wouldn't provide much compression savings with regular PNG, it would need a change to the format. But since I never had an Amiga, I'm curious to see how it looks, and how well it might scale to modern image resolutions.

Conceptually, it's not much different than 3:1 horizontal chroma subsampling, but might actually look a lot better.

Quick explainer: instead of having a 24-bit-per-pixel image, you have a 10-bit-per-pixel image, where the first two bits are a mode selector, and the last 8 bits are the actual pixel data. The modes are Hold and Modify{R,G,B}. Modify{R,G,B} modify just the red, green, or blue component of the 24-bit color for that pixel with the 8 bits specified. The modify mode assigns that pixel to be equivalent to the 8-bit value from a pre-defined palette or some pre-defined bit-assignment mode like RRRGGGBB or something. So basically, the horizontal color resolution is divided by 3, but sometimes you get lucky and there's no noticeable loss.

I realise I never did a re-#introduction after moving to my bespoke, artisanal instance. So here it is!

I'm a soon-graduating PhD student at #UBC Biomedical Engineering with a research focus on #imaging, #biomechanics and #simulation of rare pediatric hip disorders like #perthes disease.

My other interests are all over the place: #urbanism, #classiccars, #retrocomputing, #electoralreform, #crochet, #music composition, #linux and #fedi and more I'll probably add as I remember!

#PhysicsJournalClub
"Three-dimensional holographic imaging of incoherent objects through scattering media"
by Y. Baek, H. de Aguiar and @sylvaingigan
arxiv.org/abs/2502.01475
#optics #physics #imaging

As you daily experience anytime you look at anything, light scattering severely impairs your ability to image (mild scattering like mist makes things in a distance fuzzy, strong scattering like your own body makes it completely impossible to see what is happening inside or behind it). On one hand this is good, as it allows us to see where (e.g.) trees are so we don't bump into them. On the other hand there are a LOT of situations where you would really like to see what is going on behind a scattering medium (surely it would save a lot of exploratory surgeries).
The problem of imaging through a scattering medium is largely unsolvable in its most general form, but there are a lot of special cases where you can go surprisingly far, and people (me included) have spent a lot of time checking exactly how far.

In this paper the authors consider a set of small fluorescent objects behind a not-too-thick scattering medium, and look for a way to retrieve their 3D arrangement.
Problem: fluorescent emission means incoherent emission, so the phase information (which encodes a lot of information about position) is lost. Still, we can rely on the assumption that there is a finite (ideally not too large) amount of point emitters. Since each emitter is point-like, if we only measure the light that reaches us through the scattering medium at a single frequency (to be more realistic, a small bandwidth), we will see the incoherent sum of a speckle pattern per fluorescent emitter.
1/2

arXiv.orgThree-dimensional holographic imaging of incoherent objects through scattering mediaThree-dimensional (3D) high-resolution imaging is essential in microscopy, yet light scattering poses significant challenges in achieving it. Here, we present an approach to holographic imaging of spatially incoherent objects through scattering media, utilizing a virtual medium that replicates the scattering effects of the actual medium. This medium is constructed by retrieving mutually incoherent fields from the object, and exploiting the spatial correlations between them. By numerically propagating the incoherent fields through the virtual medium, we non-invasively compensate for scattering, achieving accurate 3D reconstructions of hidden objects. Experimental validation with fluorescent and synthetic incoherent objects confirms the effectiveness of this approach, opening new possibilities for advanced 3D high-resolution microscopy in scattering environments.