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Vista Thumbnail Cache

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(@twjolson)
Posts: 417
Honorable Member
Topic starter
 

On opening the 256 thumbcache file in vista, I am seeing thumbnails of folders. The thing I don't understand is they are PNG file format. I was under the impression all the larger thumbnails were jpg, and the smaller were bmp. Paging through the non-folder thumbnails seems to confirm this.

Can anyone shed some light on this? What I've seen online only confirms the jpg/bmp statement above.

 
Posted : 07/10/2011 11:17 pm
(@decanisimov)
Posts: 11
Active Member
 

I saw png images in thumbcache_256.db too. I think Windows developers decided to use png format for folder thumbnail because png has alpha channel which is important for UI (small bmp images have alpha too). Also png require less disc space.

 
Posted : 14/10/2011 12:10 pm
(@twjolson)
Posts: 417
Honorable Member
Topic starter
 

Ok, many thanks!

 
Posted : 14/10/2011 6:27 pm
(@pashapal)
Posts: 9
Active Member
 

Windows XP supports 256x256 icons, but storing it uncompressed would occupy ~400kB on disk, while storing it as PNG lends itself to much smaller sizes. Vista continued with the PNG format especially for 256x256 sized icons to ensure backward compatibility. Folder icons and any system based icons and thumbnails are always stored as PNG files. Larger icons are compressed and stored as JPEGs, and the smaller ones (for example 32x32) are stored as BMPs for faster access.

The advantage of storing it in PNG is that it provides loss-less compression, hence the quality of the icon is not lowered. The other advantage as mentioned above is the alpha channel which is not supported by JPEG or BMP

 
Posted : 03/11/2011 10:29 pm
(@decanisimov)
Posts: 11
Active Member
 

The other advantage as mentioned above is the alpha channel which is not supported by JPEG or BMP

Folder icons stored in BMP 32 bit format are stored with alpha channel too.

 
Posted : 07/11/2011 9:30 am
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