What is with phot-compression for examples?

[stickwolf]

Why the heck do all the smaller version of that brick church photo in the example galleries all show this funny spiral or circle patterns in the brick while the full size image shrunk to the same smaller *viewing* size in my browser looks clean? This seems to be irrespective of camera...

-Aaron

[Margus]

You've got a strange browser :) I can enjoy really beautiful dynamic changes of the spiral patterns when dragging the browser window border with my mouse and the image size changes accordingly.

The reason for the funny spirals is the close match of the size and direction of the regular pattern in the photo with the size and direction of the regular pattern of the display pixels.

[stickwolf]

Yeah... but, I mean... it must have something to do with the compression being used. I don't see ANY strange patterning when viewing the full-size download in any program at any size, and the patterning in the small version is there in any zoom level in any program. It is something inherently saved to the smaller file versus the full original file...

[Margus]

Ok, I got your point. Seems that the logic of the picture compression used for generating the small pictures on this site is just to ignore some of the pixels proportionally with the downsize ratio. You don't see any patterns when the compression program will calculate a new color for all pixels in a downsized image based on the average values of original nearby pixels.

I 've got one program in my computer which shows the patterns on the small version of the full size image too, it's IE7 :). Just let the IE to fit the image to the browser window and you've got the patterns.

[Jeff Keller]

The thumbnail creator I use for the galleries is pretty lousy, which is why I encourage people to view the full size images. If someone knows of a truly excellent Mac thumbnail program, please let me know.

[Margus]

No suggestions, strange.
I know that several Mac fans will hate me but... stuff the mac and use the simple plain old paintbrush in windows to produce the thumbnails without any odd patterns.

Margus

P.S. I hope you'll get some good advice for suitable Mac thumbnail programs after this post ;)

[stickwolf]

I'm really not an expert, but the very first program I tried just now was the FREE Mac software: ImageWell, and it took your same original, compressed it to 800x600 at a jpg compression that equaled the 144kb that your smaller online file had... results were only very subtle patterning, MUCH MUCH better than what you currently have online. Here, I'll attach the results. I'd bet there's tons of other options that work fine as well. I have no idea what you are using, but this FIRST try of mine was pretty good with ImageWell.

Your compressed photo:
34465

ImageWell output from your original, at same file size:
34466

Hope this helps

-Aaron

[Margus]

I can suggest a java based software called jalbum (http://jalbum.net/software/download/current), which is claimed to run on Mac too. To be totally honest I have Windows experience only myself. The jalbum software is primarily meant for making http-based photo albums but as a side effect it's a pretty powerful tool for generating thumbnails and scaled down images in batch. But - be careful to set the scaling method to "smooth".