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Thread: ec-idat (7-zip Deflate compression PNG)

  1. #1
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    ec-idat (7-zip Deflate compression PNG)

    The author of TruePNG released the new test application - ec-idat (uses for compression of PNG – 7za).
    Having carried out a number of tests with different versions 7-zip I revealed essential distinction between versions till 4.32 and after.

    Example (There is a lot of such examples):
     ec-idat -mx=9 -mfb=257 -mpass=5

    7-zip 4.32 - 1842.png - 344 239 byte
    7-zip 15.12 - 1842.png - 336 465 byte

    7-zip 4.32 - 2248.png - 413 104 byte
    7-zip 15.12 - 2248.png - 425 497 byte

    7-zip 4.32 - 3122.png - 387 678 byte
    7-zip 15.12 - 3122.png - 397 906 byte

    7-zip 4.32 - 4485.png - 426 694 byte
    7-zip 15.12 - 4485.png - 418 403 byte

    There is strong a dispersion in extent of compression depending on the version 7-zip.
    There is a question how to correct it?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	1842.png 
Views:	181 
Size:	336.0 KB 
ID:	3996   Click image for larger version. 

Name:	2248.png 
Views:	153 
Size:	403.8 KB 
ID:	3997   Click image for larger version. 

Name:	3122.png 
Views:	168 
Size:	386.8 KB 
ID:	3998   Click image for larger version. 

Name:	4485.png 
Views:	163 
Size:	413.8 KB 
ID:	3999  
    Attached Files Attached Files

  2. #2
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    Quote Originally Posted by lorents17 View Post
    There is strong a dispersion in extent of compression depending on the version 7-zip.
    There is a question how to correct it?
    This can be corrected by replacing 7-zip's deflate by zopfli's deflate algorithm.

  3. #3
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    7-zip deflate has on much higher proizvoditetlnost than zopfli. About it to the reason it is private it is necessary 7-zip to deflate. I can't resolve an issue of strong dispersion in compression 7-zip deflate in any way.

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    I would recommend contacting Igor Pavlov (7-zip Author) for advise as change may be resulted of other default settings which can be set by ec-idat program if can be easily recognized.

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  6. #6
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    Quote Originally Posted by lorents17 View Post
    7-zip deflate has on much higher proizvoditetlnost than zopfli.
    proizvoditetlnost == efficiency?

    As far as I know zopfli is still the leader in deflate compression density.

    For example Canterbury compression:
    zopfli: 669’933 bytes
    kzip: 674’321 bytes
    7-zip: 675’163 bytes
    gzip -9: 730’732 bytes

    See more compression results in https://zopfli.googlecode.com/files/...ing_Zopfli.pdf

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    TurboBench: - Sun Dec 27 2015

    Code:
          C Size  ratio%     C MB/s     D MB/s   Name            File              (bold = pareto) MB=1.000.0000
          332031    31.6       0.14     331.52   zopfli          1842.png
          336465                                 7-zip 15.12     1842.png
          356283    34.0       6.43     316.24   zlib 9          1842.png
    
          406451    38.7       0.16     314.23   zopfli          2248.png
          413104                                 7-zip 4.32      2248.png
          425497                                 7-zip 15.12     2248.png
          434850    41.4      11.69     266.99   zlib 9          2248.png

  8. #8
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    I meant 7-zip deflate has the high speed of compression

    Compression algorithm Compression time
    gzip *9 5.60 s
    7*zip *mm=Deflate *mx=9 128 s
    kzip 336 s
    Zopfli 454 s

  9. #9
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    performance is better translation 8-)

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