[gdal-dev] GDALwarp creates some darker images after update from 1.7.0b2 to GDAL 1.11.0

[Marcel Blom]

Hi Even,

I uploaded stuff for testing in Dropbox : 
https://www.dropbox.com/sh/0f1zrs295s75u5n/AAAZI2tTokaYZtJ6cfj9zxe0a?dl=0

Because I had too much data I wanted to use lower resolution files and 
guess what? On other resolutions the problems were gone.
So it might have something to do with size/resolution..(?)
I also tested warping direct from one source file and the results were 
the same. But because I use a VRT with multiple source files I added a 
VRT file and made these target files via the VRT file.
I have only space to upload one source file. When I used multiple source 
files in the VRT the target file was even darker (svt-08+.bmp)

I uploaded :
- !buildvrt.bat (with commands to build the VRT file)
- !warp.bat (with commands to warp the VRT into target files)
- _Source.tif (as source file)
- _gdalbuild.vrt (as VRT file)

Resulting target files:
- svt-02.bmp (Source > VRT > Target 2048x2048 = normal)
- svt-04.bmp (Source > VRT > Target 4096x4096 = normal)
- svt-08.bmp (Source > VRT > Target 8192x8192 = darker)
- svt-08+.bmp (Source > VRT with multiple files > Target 8192x8192 = 
even darker)
- svt-16.bmp (Source > VRT > Target 16384x16384 = normal)

Really strange.
I didn't see this behaviour with the older GDAL.

Marcel

Even Rouault schreef op 26-9-2014 om 19:46:
> Marcel,
>
> The best would be that you prepare something that others can try in a fully
> reproducable way, i.e. provide source(s) image(s) and all the exact command
> lines you use.
>
> Even
>
> Le vendredi 26 septembre 2014 19:41:01, Marcel Blom a écrit :
>> Because of some problems with GDAL 1.7.0b2 in FWTools 2.4.7 I upgraded
>> to GDAL 1.11.0 in the latest OSGeo4W distro. This solved some issues I
>> had, but introduced a really annoying one and what ever I do I can't get
>> rid off it. I hope someone can help me out. If BTW I try to go back to
>> GDAL 1.7.0b2 with FWTools the problem is still there, so I guess it's a
>> (new) driver/DLL update issue.
>>
>> My problem looks exactly like this post... GDAL TIF to JPG Creates Dark
>> Image
>> <http://gis.stackexchange.com/questions/101393/gdal-tif-to-jpg-creates-dark
>> -image> Only that I don't use JPG. And I use GDALwarp. And not all target
>> files have the problem. Most target files look OK. And I only see it with
>> Aerial Photo like sources. With vector like raster sources I don't see the
>> problem. So when reading the other post I thought it had to do with a
>> mask/alpha channel or something, but I can't see this in the source. And
>> whatever option I test, the problem remains.
>>
>> I already created a post here :
>> http://gis.stackexchange.com/questions/114526/gdalwarp-creates-darker-targe
>> t-image-sometimes But I had no final answer... And I think this is the
>> right place to ask.
>>
>> Here are two screenshots. One from the source (Tiff) and one from a
>> intersection of four target files (Tiff or BMP)
>>
>> Section of Source :
>> https://www.dropbox.com/s/gy2tu0h8dufv41o/Source.jpg?dl=0
>>
>> Intersection of four Target files :
>> https://www.dropbox.com/s/av7mdj8ivx3zgsl/Target.jpg?dl=0
>>
>> The source I use is 8bit/channel RGB JPEG. And the merged Tiff is
>> 8bit/channel RGB.
>> I tested almost all options in multiple actions in my workflow. So
>> cutting the source with gdaltranslate in smaller parts for editing.
>> Building a VRT with gdalbuildvrt and cutting into final parts with
>> gdalwarp which will show the problem.
>>
>> I started with the -b 1 -b 2 -b 3 option in my gdalbuildvrt action, but
>> GDAL crashes here... (?) I also tested other options that might have
>> something to do with the problem... -nomd -co ALPHA=YES/No -co
>> PHOTOMETRIC=RGBA/RGB -setci, you name it...
>>
>> I checked good and bad source and target areas with gdalcompare and
>> gdalinfo, but I saw nothing strange...
>>
>> I'm now thinking of resetting GDAL driver settings if that is possible..(?)
>>
>> Has anyone seen this before? Can anyone give me a hint..?