Re: Issue with PNG and Blog inw Windows using MinGW64

On Wed, 21 Dec 2016, Giovanni Remigi wrote:

> I'm aware that GraphicsMagick does not support files containing UTF
> characters on Windows. I'm using GraphicsMagick as a DLL and If I try
> reading from such files my application crashes.

By "UTF characters" do you mean UTF-16?  GraphicsMagick can work ok 
with UTF-8.  What do you mean by "files containing UTF characters on 
Windows"?

> I found a workaround reading an image into a Blob using Qt and then reading
> the Blob from memory using GraphicsMagick. This works perfectly but I have
> an issue with the opposite operation writing a Blob into a file.
>
> When I encode an Image into a Blob in PNG format using Graphics Magick and
> I write the Blob into a file using Qt I experience a data loss. The last
> part of the image appears black.
> The problem happens only *with big PNG* ( > 32MB) and* on WIndows only*,
> while on Linux it works perfectly.

I don't know anything about QByteArray but it seems to me 
that bytesWritten should equal blob.length() on success.

> I somehow blame libpng16. On Linux I use libpng12. Using the JPEG format I
> do not experience data loss.

Are you sure that your Qt build is using a consistent libpng version? 
Is it possible that Qt is built against a different libpng than 
GraphicsMagick was built against?

Bob
-- 
Bob Friesenhahn
[email protected], http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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