ec-idat (7-zip Deflate compression PNG)

[lorents17]

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?

[Jyrki Alakuijala]

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.

[lorents17]

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.

[maadjordan]

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.

[lorents17]

I tried, but without rezultatno.
https://sourceforge.net/p/sevenzip/d...read/54b32538/

[Jyrki Alakuijala]

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

[dnd]

      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

[lorents17]

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

[necros]

performance is better translation 8-)