[mapserver-users] Corrupted PNG issue

Even Rouault even.rouault at spatialys.com
Fri Nov 19 05:07:25 PST 2021 

Could be a msIO_needBinaryStdout() missing somewhere. Seth, if you've 
the chance to run a git bisect session, that could probably give a 
strong hint of how to fix that.

Le 19/11/2021 à 09:43, Seth G a écrit :
> Possibly unrelated but I ran into a similar issue exporting WFS to 
> zipped shapefiles.
> Working fine in 7-4-3 but broken in 7-6-4 (and current master) - the 
> zip files are corrupt, although they have an identical size.
>
> 7-zip reports "Headers Error Unconfirmed start of archive"
>
> The same command is used for both versions:
>
> mapserv -nh 
> "QUERY_STRING=map=my.map&service=WFS&REQUEST=GetFeature&TYPENAME=LayerName&version=2.0.0&outputformat=shapezip&srsName=EPSG:3857" 
> > output.zip
>
> I had a look with a hex editor but the start of the working and 
> corrupt zips seem identical.
>
> On the other hand all PNGs / WMS services are fine.
>
> Seth
>
>
> --
> web:http://geographika.co.uk
> twitter: @geographika
>
>
> On Thu, Nov 18, 2021, at 3:53 PM, Steve Lime wrote:
>> Hmmm... I've not run into or heard of this before although I'm not a 
>> windows user. I did a quick sanity check with a mapfile here and the 
>> latest 7.4 and 7.6 versions. While not exactly the same setup you 
>> have in terms of versions, they produce the exact same png image.
>>
>> What do you get for output if you use mapserv.exe at the command 
>> line? So something like:
>>
>>   mapserv.exe -nh "QUERY_STRING= 
>> map=dynamic\5708d96b-c606-4c35-95e7-085fedc1dcce.map&SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&FORMAT=image%2Fpng&TRANSPARENT=true&LAYERS=MAP&TILED=true&WIDTH=512&HEIGHT=512&CRS=EPSG%3A3857&STYLES=&BBOX=-10877294.873093722%2C5536486.832751887%2C-10876071.880641159%2C5537709.82520445" 
>> > test.png
>>
>> That would take PostMan and the web server out of the picture. Is 
>> there any chance different versions of libpng are being used? What 
>> are you using to manage the tiles?
>>
>> --Steve
>>
>> On Wed, Nov 17, 2021 at 4:57 PM John Huotari via MapServer-users 
>> <mapserver-users at lists.osgeo.org 
>> <mailto:mapserver-users at lists.osgeo.org>> wrote:
>>
>>     I’m attempting to upgrade from MapServer 7.6.1 to 7.6.4 via
>>     compiled packages obtained from GISInternals.  I’m running it on
>>     Windows/IIS and whereas 7.6.1 was generating .PNG tiles perfectly
>>     for me, after upgrading to 7.6.4, the .PNGs being created appear
>>     to be corrupt.  I can replace the 7.6.4 exe and dlls with 7.6.1
>>     versions and the PNG images generate fine again, so while there
>>     are quite a few places that could introduce an issue, with the
>>     exception of a change to MapServer everything would be identical
>>     in my stack between having the issue in 7.6.4 and not in 7.6.1.
>>
>>
>>     The good headers from 7.6.1 look like this
>>
>>
>>     89 50 4e 47 0d 0a 1a 0a  00 00 00 0d 49 48 44 52
>>
>>
>>     and the corrupted ones from 7.6.4 look like this
>>
>>
>>     89 50 4e 47 0d 0d 0a 1a 0d 0a 00 00 00 0d 49 48 44 52
>>
>>
>>     It appears that the 0a values from the valid header are being
>>     converted to 0d 0a.  I might be wrong here, but it appears to me
>>     that something is interpreting the 0a as a line feed and given
>>     the code is running on Windows, is converting that LF into a CR
>>     LF.  The replacement doesn’t seem to be limited to the file
>>     header as I see the 7.6.4 version of the file is slightly larger
>>     (18,571 bytes instead of 18,407 bytes) and in spot checking, I’ve
>>     verified some additional 0d’s exist precede 0a within the data
>>     blocks of the .PNG.  Has anyone experienced anything like this or
>>     know of any fixes?
>>
>>
>>     PNG Images produced on the server with shp2img are just fine,
>>     it’s only images produced by making a WMS request to mapserv.exe
>>     that have the issue.  An example WMS request would be
>>
>>
>>     https://<Server Name
>>     Removed>/mapserv.exe?map=dynamic\5708d96b-c606-4c35-95e7-085fedc1dcce.map&SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&FORMAT=image%2Fpng&TRANSPARENT=true&LAYERS=MAP&TILED=true&WIDTH=512&HEIGHT=512&CRS=EPSG%3A3857&STYLES=&BBOX=-10877294.873093722%2C5536486.832751887%2C-10876071.880641159%2C5537709.82520445
>>
>>
>>     Maybe I’m completely misdiagnosing the problem as these PNG image
>>     files just show up as corrupted within a browser – for example
>>     FireFox reports “The image <full URL here> cannot be displayed
>>     because it contains errors.”  The way I obtained the actual .PNG
>>     images to view in a binary editor was to use PostMan and save the
>>     body of the results.  Perhaps PostMan introduced the extra bytes
>>     when saving an unrecognizable format file to disk whereas it did
>>     not when saving a file it recognized as a valid PNG.  I can’t
>>     find anything different between the valid and invalid files
>>     beyond the extra 0d’s that have been added though, so I don’t
>>     think PostMan or anything else in the chain introduced them.
>>
>>
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