zapped Posted October 14, 2004 Share Posted October 14, 2004 I wanted to recommend the latest version of the freeware IrfanView (3.92) to someone who was looking for an economical (i.e. free) way to batch-compress some large Tif files. Out of curiosity I took the same uncompressed Tif file and applied both LZW-Tif and Zip-Tif compression using the "Save As" dialog in both Photoshop/CS and IrfanView 3.92. To my surprise, the compressed files in Irfanview were larger than the compressed files in Photoshop, even though both compression methods are lossless AND each compressed file could be re-opened in either PS/CS or IrfanView! Specifically, I started with a smallish 9235KB uncompressed Tif file (no layers, no channels), with lots of detail in the image. Photoshop produced a 5988KB LZW-Tif and a 5415KB Zip-Tif. Irfanview produced a 8063KB LZW-Tif and a 6388KB ZIP-Tif. Yeah, I know, you get what you pay for. But does anyone have any idea why this discrepancy exists, or how I can get the freeware IrfanView to produce more compact (but still lossless) Tif files? Link to comment Share on other sites More sharing options...
peter_foiles2 Posted October 14, 2004 Share Posted October 14, 2004 Back in the days when zip and similar compression schemes became popular there was always a tradeoff between zipping it fast or zipping it small. The point is that even though the same conpression algorithim is being used how that algorithim is implemented still affects how much compression occurs. What you have dixcovered is that the compression software in PS is more sophisticated than that in IrfanView. Given that one is developed by a major corporation with lots of resources and the other by an individual with limited resources this should not be suprising. If you want IrfanView to compress better find a compression software hotshot who is willing to give the IrvanView some free consultation. Link to comment Share on other sites More sharing options...
oskar_ojala Posted October 14, 2004 Share Posted October 14, 2004 I don't remember how LZW differed from the LZ78 description, but the dictionary size might vary. Zip is based on the LZ77 paper and typical implementations many different strengths of compression, with less compression being faster to process. If you want good compression with a fairly clean format, try PNG, you will get better compression than with TIFF (provided that the implementation isn't very bad...) Link to comment Share on other sites More sharing options...
mattb1 Posted October 14, 2004 Share Posted October 14, 2004 I didn't see anything in irfan view that inspired confidence in me, the compression algorithms were just the most obvious. It seemed more egoware than actually delivering on its promises. That is the 'look at what I can do' factor. Buyer be ware. It depends on how they implemented the algorithms. They could have written the code, or obtained it from a thrid party, but it seems unlikely that it was an industrial source. And, just because the files are readable by photoshop doesn't mean that all photo editors can read them or that they will work in future releases. My day job is programming, and you would be surprised how and where the most innocent of mistakes show up. We all make them, but who knows how many from someone you don't know. I would rather put stock in a software suite that has gone through rigorous testing by real world users, than put my photos at risk. Link to comment Share on other sites More sharing options...
mendel_leisk Posted October 14, 2004 Share Posted October 14, 2004 Vuescan is one program I've found that does decent lzw compression, takes tiffs down to about 70~75% of orig. size. If you make it work for your application. I found ps lzw to be less than useless, it would sometimes increase file size. Link to comment Share on other sites More sharing options...
sean de merchant httpw Posted October 14, 2004 Share Posted October 14, 2004 Just a thought, it is a bit CPU intensive, but lossless JPEG 2000 should get your image down below the 4 MB mark. If you really need to save space, then that is the way to go. For those without CS, you can pick up a <a href=http://www.fnordware.com/j2k/>freeware implementation from Fnord</a>. A quick test on a 16-bit color image (12 bpp source) drops the size from 28.8 MB down to 17 MB. And the same image converted to 8 bit color converts from 14.4 MB down to 4469 KB. So efficiency is still better in a worse case scenario for that image and the compression is still lossless.<p> some thoughts,<p> Sean <p> <a href=http://www.tearnet.com/sean>http://www.tearnet.com/sean</a> Link to comment Share on other sites More sharing options...
zapped Posted October 14, 2004 Author Share Posted October 14, 2004 Thanks Sean, that JP2000 plugin works great in Photoshop. Doesn't really solve the problem for the person looking for a freeware solution, but I'm glad to add it to *my* toolbelt. Link to comment Share on other sites More sharing options...
bill_tuthill Posted October 16, 2004 Share Posted October 16, 2004 LZW compression is unavailable in freeware due to Unisys patent enforcement. As Oskar suggested, use PNG and get over it. Link to comment Share on other sites More sharing options...
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