kicad-developers team mailing list archive

[Wayne Stambaugh <stambaughw@xxxxxxxxxxx>]

On 8/29/2011 10:39 PM, Dick Hollenbeck wrote:
> 
>> On 08/29/2011 05:47 PM, fabrizio wrote:
>>
>>> 3)  .png generation from .svg.Are you using the script I made (scr/mk_png)?
>> I am using the same exact steps and technique, but from CMake on an image by
>> image basis, rather than a group step by group step basis.
> 
> 
> You did well to find these steps, Fabrizio.
> 
> 
> I have discovered that there are 3 or 4 "tEXt" chunks (i.e. records) in the
> final PNGs, where the inkcape dude is telling about his name, inkscape's name,
> and the date of creation.

Dick,

I just tried exporting a few SVGs to PNGs using InkScape on both Windows and
Linux and I only get a single tEXt chunk with the Inkscape information.

> 
> I'd like to remove all 3 or 4 of these to save space in the kicad programs,
> since all these will be in memory as JPG files.  The shear number of PNGs
> increases this justification.
> 
> To see them, do:
> 
> $ hexdump -C some.png | less
> 
> 
> 000005d0  1b 7f 4e 4e 69 77 41 7a  00 00 00 14 74 45 58 74  |..NNiwAz....tEXt|
> 000005e0  41 75 74 68 6f 72 00 4a  61 6b 75 62 20 53 74 65  |Author.Jakub Ste|
> 000005f0  69 6e 65 72 e6 fb f7 2f  00 00 00 25 74 45 58 74  |iner.../...%tEXt|
> 00000600  64 61 74 65 3a 63 72 65  61 74 65 00 32 30 31 31  |date:create.2011|
> 00000610  2d 30 38 2d 32 38 54 31  30 3a 32 39 3a 33 35 2d  |-08-28T10:29:35-|
> 00000620  30 35 3a 30 30 c7 99 61  14 00 00 00 25 74 45 58  |05:00..a....%tEX|
> 00000630  74 64 61 74 65 3a 6d 6f  64 69 66 79 00 32 30 31  |tdate:modify.201|
> 00000640  31 2d 30 38 2d 32 38 54  31 30 3a 32 39 3a 33 35  |1-08-28T10:29:35|
> 00000650  2d 30 35 3a 30 30 b6 c4  d9 a8 00 00 00 19 74 45  |-05:00........tE|
> 00000660  58 74 53 6f 66 74 77 61  72 65 00 77 77 77 2e 69  |XtSoftware.www.i|
> 00000670  6e 6b 73 63 61 70 65 2e  6f 72 67 9b ee 3c 1a 00  |nkscape.org..<..|
> 00000680  00 00 00 49 45 4e 44 ae  42 60 82                 |...IEND.B`.|
> 
> 
> Your imagemagick composite step moves these chunks to the end of the file,
> inkscape had them up front.
> 
> 
> I tried:
> 
> $ pngcrush -rem text some.png
> 
> and it removes only one at a time, so I had to run it 3 or 4 times.

Have you tried the alla or allb -rem option?

>From the pngcrush man page:

To do surgery with a chain-saw, -rem alla removes all known ancillary chunks
except for tRNS, and -rem allb removes all but tRNS and gAMA.

I particularly like the chainsaw reference.  I would test it myself but I can't
seem to generate a PNG file with multiple text chucks to test it on and I'm not
motivated enough to manually edit at PNG file with a hex editor just to try it out.

Wayne


> 
> And perhaps that is the best we can do.  Searched all around the internet and
> could not find a tool to do this in one pass, removing all 3 or 4 "tEXt" chunks
> in one pass.  Thinking about writing a C program to do it in one pass.  Don't
> feel like patching pngcrush, since the source is *ugly* and life is short.
> 
> Hoping for a miracle at this point, to avoid the 1.5 hours time for me to do it.
> 
> If someone could track down the author of pngcrush, and whine, get it fixed,
> that might qualify as a miracle.  Or if someone can find a free tool that
> actually works in this regard, that would be helpful.  Or if someone wants to
> write a program to do it that can become part of the source tree, you will be my
> hero.  PNG file format is cake, just a series of well defined records, which you
> preserve and write back out, with a header up front.  Drop the "tEXt" records
> please.
> 
> 
> Dick
> 
> 
> 
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