we will use “pngcrush -v -n file.png” to display file informations

| pngcrush 1.5.10, Copyright (C) 1998-2002 Glenn Randers-Pehrson
| This is a free, open-source program. Permission is irrevocably
| granted to everyone to use this version of pngcrush without
| payment of any fee.
| Executable name is pngcrush
| It was built with libpng version 1.2.4, and is
| running with libpng version 1.2.4 - July 8, 2002 (header)
| Copyright (C) 1998-2002 Glenn Randers-Pehrson,
| Copyright (C) 1996, 1997 Andreas Dilger,
| Copyright (C) 1995, Guy Eric Schalnat, Group 42 Inc.,
| and zlib version 1.1.4pc, Copyright (C) 1998,
| Jean-loup Gailly and Mark Adler.
| It was compiled with gcc version 2.95.2 19991024 (release)
| and as version 2.9.5
| under DJGPP 2.3, Copyright (C) 1995, D. J. Delorie
| and loaded with PMODE/DJ, by Thomas Pytel and Matthias Grimrath
| Copyright (C) 1996, Matthias Grimrath.

Reading IHDR chunk, length = 13.
Reading tIME chunk, length = 7.
Reading pHYs chunk, length = 9.
Reading IDAT chunk, length = 27740.
Reading IEND chunk, length = 0.
Recompressing F:\DAUPHIN.png
Total length of data found in IDAT chunks = 27740
IHDR chunk data:
Width=737, height=472
Bit depth =8
Color type=2
Interlace =0
Setting IHDR
CPU time used = 0.000 seconds (decoding 0.000,
encoding 0.000, other 0.000 seconds)

| pngcrush 1.5.10, Copyright (C) 1998-2002 Glenn Randers-Pehrson
| This is a free, open-source program. Permission is irrevocably
| granted to everyone to use this version of pngcrush without
| payment of any fee.
| Executable name is pngcrush
| It was built with libpng version 1.2.4, and is
| running with libpng version 1.2.4 - July 8, 2002 (header)
| Copyright (C) 1998-2002 Glenn Randers-Pehrson,
| Copyright (C) 1996, 1997 Andreas Dilger,
| Copyright (C) 1995, Guy Eric Schalnat, Group 42 Inc.,
| and zlib version 1.1.4pc, Copyright (C) 1998,
| Jean-loup Gailly and Mark Adler.
| It was compiled with gcc version 2.95.2 19991024 (release)
| and as version 2.9.5
| under DJGPP 2.3, Copyright (C) 1995, D. J. Delorie
| and loaded with PMODE/DJ, by Thomas Pytel and Matthias Grimrath
| Copyright (C) 1996, Matthias Grimrath.

Reading IHDR chunk, length = 13.
Reading pHYs chunk, length = 9.
Reading iCCP chunk, length = 2617.
Reading gAMA chunk, length = 4.
Reading cHRM chunk, length = 32.
Reading IDAT chunk, length = 53632.
Reading IEND chunk, length = 0.
Recompressing F:\DAUPHIN_.png
Total length of data found in IDAT chunks = 53632
IHDR chunk data:
Width=737, height=472
Bit depth =8
Color type=2
Interlace =0
Setting IHDR
gamma=(45454/100000)
Got iccp chunk, proflen=3144
CPU time used = 0.055 seconds (decoding 0.055,
encoding 0.000, other 0.000 seconds)

| pngcrush 1.5.10, Copyright (C) 1998-2002 Glenn Randers-Pehrson
| This is a free, open-source program. Permission is irrevocably
| granted to everyone to use this version of pngcrush without
| payment of any fee.
| Executable name is pngcrush
| It was built with libpng version 1.2.4, and is
| running with libpng version 1.2.4 - July 8, 2002 (header)
| Copyright (C) 1998-2002 Glenn Randers-Pehrson,
| Copyright (C) 1996, 1997 Andreas Dilger,
| Copyright (C) 1995, Guy Eric Schalnat, Group 42 Inc.,
| and zlib version 1.1.4pc, Copyright (C) 1998,
| Jean-loup Gailly and Mark Adler.
| It was compiled with gcc version 2.95.2 19991024 (release)
| and as version 2.9.5
| under DJGPP 2.3, Copyright (C) 1995, D. J. Delorie
| and loaded with PMODE/DJ, by Thomas Pytel and Matthias Grimrath
| Copyright (C) 1996, Matthias Grimrath.

Reading IHDR chunk, length = 13.
Reading tIME chunk, length = 7.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 7251.
Reading IEND chunk, length = 0.
Recompressing F:\DAUPHIN_acd.png
Total length of data found in IDAT chunks = 48211
IHDR chunk data:
Width=737, height=472
Bit depth =8
Color type=2
Interlace =0
Setting IHDR
CPU time used = 0.000 seconds (decoding 0.000,
encoding 0.000, other 0.000 seconds)

| pngcrush 1.5.10, Copyright (C) 1998-2002 Glenn Randers-Pehrson
| This is a free, open-source program. Permission is irrevocably
| granted to everyone to use this version of pngcrush without
| payment of any fee.
| Executable name is pngcrush
| It was built with libpng version 1.2.4, and is
| running with libpng version 1.2.4 - July 8, 2002 (header)
| Copyright (C) 1998-2002 Glenn Randers-Pehrson,
| Copyright (C) 1996, 1997 Andreas Dilger,
| Copyright (C) 1995, Guy Eric Schalnat, Group 42 Inc.,
| and zlib version 1.1.4pc, Copyright (C) 1998,
| Jean-loup Gailly and Mark Adler.
| It was compiled with gcc version 2.95.2 19991024 (release)
| and as version 2.9.5
| under DJGPP 2.3, Copyright (C) 1995, D. J. Delorie
| and loaded with PMODE/DJ, by Thomas Pytel and Matthias Grimrath
| Copyright (C) 1996, Matthias Grimrath.

Reading IHDR chunk, length = 13.
Reading pHYs chunk, length = 9.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 5939.
Reading IEND chunk, length = 0.
Recompressing F:\\DAUPHIN_xn.png
Total length of data found in IDAT chunks = 46899
IHDR chunk data:
Width=737, height=472
Bit depth =8
Color type=2
Interlace =0
Setting IHDR
CPU time used = 0.055 seconds (decoding 0.055,
encoding 0.000, other 0.000 seconds)

| pngcrush 1.5.10, Copyright (C) 1998-2002 Glenn Randers-Pehrson
| This is a free, open-source program. Permission is irrevocably
| granted to everyone to use this version of pngcrush without
| payment of any fee.
| Executable name is pngcrush
| It was built with libpng version 1.2.4, and is
| running with libpng version 1.2.4 - July 8, 2002 (header)
| Copyright (C) 1998-2002 Glenn Randers-Pehrson,
| Copyright (C) 1996, 1997 Andreas Dilger,
| Copyright (C) 1995, Guy Eric Schalnat, Group 42 Inc.,
| and zlib version 1.1.4pc, Copyright (C) 1998,
| Jean-loup Gailly and Mark Adler.
| It was compiled with gcc version 2.95.2 19991024 (release)
| and as version 2.9.5
| under DJGPP 2.3, Copyright (C) 1995, D. J. Delorie
| and loaded with PMODE/DJ, by Thomas Pytel and Matthias Grimrath
| Copyright (C) 1996, Matthias Grimrath.

Reading IHDR chunk, length = 13.
Reading tEXt chunk, length = 11.
Reading tEXt chunk, length = 16.
Reading tEXt chunk, length = 10.
Reading tEXt chunk, length = 14.
Reading tIME chunk, length = 7.
Reading pHYs chunk, length = 9.
Reading gAMA chunk, length = 4.
Reading IDAT chunk, length = 45857.
Reading IEND chunk, length = 0.
Recompressing F:\DAUPHIN_psd_psp.png
Total length of data found in IDAT chunks = 45857
IHDR chunk data:
Width=737, height=472
Bit depth =8
Color type=2
Interlace =0
Setting IHDR
gamma=(45455/100000)
0 Title: titre
1 Description: desc
2 Author: nom
3 Copyright: copy
CPU time used = 0.055 seconds (decoding 0.055,
encoding 0.000, other 0.000 seconds)

| pngcrush 1.5.10, Copyright (C) 1998-2002 Glenn Randers-Pehrson
| This is a free, open-source program. Permission is irrevocably
| granted to everyone to use this version of pngcrush without
| payment of any fee.
| Executable name is pngcrush
| It was built with libpng version 1.2.4, and is
| running with libpng version 1.2.4 - July 8, 2002 (header)
| Copyright (C) 1998-2002 Glenn Randers-Pehrson,
| Copyright (C) 1996, 1997 Andreas Dilger,
| Copyright (C) 1995, Guy Eric Schalnat, Group 42 Inc.,
| and zlib version 1.1.4pc, Copyright (C) 1998,
| Jean-loup Gailly and Mark Adler.
| It was compiled with gcc version 2.95.2 19991024 (release)
| and as version 2.9.5
| under DJGPP 2.3, Copyright (C) 1995, D. J. Delorie
| and loaded with PMODE/DJ, by Thomas Pytel and Matthias Grimrath
| Copyright (C) 1996, Matthias Grimrath.

Reading IHDR chunk, length = 13.
Reading pHYs chunk, length = 9.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 8192.
Reading IDAT chunk, length = 5939.
Reading IEND chunk, length = 0.
Recompressing F:\cdagraver\NashCDmix5\nashcd13\Internet\DAUPHIN_irf.png
Total length of data found in IDAT chunks = 46899
IHDR chunk data:
Width=737, height=472
Bit depth =8
Color type=2
Interlace =0
Setting IHDR
CPU time used = 0.000 seconds (decoding 0.000,
encoding 0.000, other 0.000 seconds)

• photoshop
  • produce biggest file
  • add gamma
  • icc and chrm chunk !!
  • remove time chunk don't insert text information in file (don't read it too)
• acdsee
  • remove phys chunk
  • but the idat chunk are split in 8kbyte recompress it with pngcrush, merge all those chunk
  • with a photoshop png file, results are the same
• xnview or irfanview
  • png of exact same size ! )
  • remove time chunk
  • idat chunk are split in 8kbyte
  • with a photoshop png file, results are the same
• paint shop pro
  • add gamma and text chunk !
  • insert text information in file
  • with a photoshop png file, results are the same

to update your file to use most PNG feature, use photoshop, and recompress your file using pngcrush forget about adding text chunk for the moment, cause no tool is able to add them, without loosing another chunks

do NOT save in interlaced. you'll get a bigger file.