Re: png image scrambled

Pavel Zlatovratskii <[email protected]> Fri, 23 Aug 2019 22:44:40 +0300
Newsgroups	gmane.comp.graphics.png.general
Organization	TB.Budget
Message-ID	<[email protected]>
This is a multi-part message in MIME format.
--------------70F1B69BCDC5D0705D2E3DCB
Content-Type: multipart/alternative;
 boundary="------------E4F2FF56703F35AC58DAE66F"


--------------E4F2FF56703F35AC58DAE66F
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit

It's not looks like a bug in libpng and not corrupted image.

Your image use fully transparent black as background using tRNS chunk. 
Some software use neutral (grey or white) background and image looks 
good. Other ignore transparency (and they are allowed to do so as tRNS 
is an ancillary chunk) and draw background with original black colour.

You can check modified picture: three bytes black to white and four 
bytes of CRC changed.

23.08.2019 17:45, Roland Winkler:
> The attached png image is not displayed correctly, and I am trying
> to find out the cause of this.
>
> I am not a png expert.  I ran into this because GNU Emacs (that uses
> libpng) does not display this image as expected, unlike other
> applications including eog and imagemagick.
>
> Then I built the test program rpng.  It displays this image in the
> same scrambled way as emacs.  Is this due to a corrupted image (that
> other applications handle more graciously) or is this a bug in libpng?
>
> Thanks.
>
>
>
> _______________________________________________
> png-mng-misc mailing list
> [email protected]
> https://lists.sourceforge.net/lists/listinfo/png-mng-misc

-- 
Have a nice DOS.

Pavel Zlatovratskii scondo-JGs/[email protected]; [email protected]


--------------E4F2FF56703F35AC58DAE66F
Content-Type: text/html; charset=windows-1252
Content-Transfer-Encoding: 7bit

<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html;
      charset=windows-1252">
  </head>
  <body text="#000000" bgcolor="#FFFFFF">
    <p>It's not looks like a bug in libpng and not corrupted image.</p>
    <p>Your image use fully transparent black as background using tRNS
      chunk. Some software use neutral (grey or white) background and
      image looks good. Other ignore transparency (and they are allowed
      to do so as tRNS is an ancillary chunk) and draw background with
      original black colour.</p>
    <p>You can check modified picture: three bytes black to white and
      four bytes of CRC changed.</p>
    <div class="moz-cite-prefix">23.08.2019 17:45, Roland Winkler:<br>
    </div>
    <blockquote type="cite"
      cite="mid:64545.25810.965606.23903-4mDQ13Tdud8Jw5R7aSpS0dP8p4LwMBBS@public.gmane.org">
      <pre class="moz-quote-pre" wrap="">The attached png image is not displayed correctly, and I am trying
to find out the cause of this.

I am not a png expert.  I ran into this because GNU Emacs (that uses
libpng) does not display this image as expected, unlike other
applications including eog and imagemagick.

Then I built the test program rpng.  It displays this image in the
same scrambled way as emacs.  Is this due to a corrupted image (that
other applications handle more graciously) or is this a bug in libpng?

Thanks.

</pre>
      <br>
      <fieldset class="mimeAttachmentHeader"></fieldset>
      <br>
      <fieldset class="mimeAttachmentHeader"></fieldset>
      <pre class="moz-quote-pre" wrap="">_______________________________________________
png-mng-misc mailing list
<a class="moz-txt-link-abbreviated" href="mailto:[email protected]">[email protected]</a>
<a class="moz-txt-link-freetext" href="https://lists.sourceforge.net/lists/listinfo/png-mng-misc">https://lists.sourceforge.net/lists/listinfo/png-mng-misc</a>
</pre>
    </blockquote>
    <pre class="moz-signature" cols="72">-- 
Have a nice DOS.

Pavel Zlatovratskii <a class="moz-txt-link-abbreviated" href="mailto:scondo-JGs/[email protected]">scondo-JGs/[email protected]</a>; <a class="moz-txt-link-abbreviated" href="mailto:[email protected]">[email protected]</a>
</pre>
  </body>
</html>

--------------E4F2FF56703F35AC58DAE66F--

--------------70F1B69BCDC5D0705D2E3DCB
Content-Type: image/png;
 name="picture_.png"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
 filename="picture_.png"

iVBORw0KGgoAAAANSUhEUgAAABEAAAARCAMAAAAMs7fIAAAAAXNSR0IArs4c6QAAAGBQTFRF
////AAAAAABmADqQAGa2OgA6OgBmOjqQOma2OpDbZgAAZgA6ZgBmZjqQZmY6ZmZmZpDbZrb/
kDoAkNv/tmYAtmY6ttv/tv//25A627Zm29uQ2////7Zm/9uQ//+2///b5sL6ZQAAAAF0Uk5T
AEDm2GYAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAAZdEVYdFNvZnR3YXJlAE1pY3Jvc29mdCBP
ZmZpY2V/7TVxAAAAgklEQVQoU62PaxKCMAyEEwEFEZA+pAhN739LN53BcgD2RyfJJt9siS6T
42ojeXL3J8rUW6Id40Px7WCHskJhVt9j75C30lt5LQUzbMl08XHCtIBUa8a4Wl9FxmacUe4T
XEoGdTI3YGT46m1gbYKm8fZM03Pm7Jag9w8hRhnkjzmu6QdI+QcKQtQBswAAAABJRU5ErkJg
gg==
--------------70F1B69BCDC5D0705D2E3DCB
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline


--------------70F1B69BCDC5D0705D2E3DCB
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

_______________________________________________
png-mng-misc mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/png-mng-misc

--------------70F1B69BCDC5D0705D2E3DCB--