[pdal] writers.gdal produces "corrupt" PNGs?

[Adam Steer]

One thing we’re looking at is using GDAL’s MEM driver, I’ll try it and see - unfortunately my c++ experience is limited to changing the names of includes…  :/ but i can test things!

Cheers

Adam



> On 1 Aug 2017, at 3:24 am, Howard Butler <howard at hobu.co> wrote:
> 
> There's a ticket to improve PDAL's writers.gdal to support more options and output data types. That will make things work better, but the development hasn't happened quite yet.
> 
> Stick with outputting GeoTIFF for now and then do gdal_translate/gdalwarp as you need as Adam's describing.
> 
> https://github.com/PDAL/PDAL/issues/1497
> 
> Howard
> 
>> On Jul 30, 2017, at 11:28 PM, Adam Steer <Adam.Steer at anu.edu.au> wrote:
>> 
>> Hi all
>> 
>> finally got to some testing with this.
>> 
>> Input: a LAS tile
>> Expected outputs: PNG files showing grayscale images of point attributes, gridded according to some input parameters about cell sizing
>> 
>> I think what happens here is that PNG expects 3 bands, and I’m trying to make greyscale images. After a lot of trying GDAL options, I ended up just writing out a GeoTIFF and then using gdal_translate to carve out my PNGs, eg:
>> 
>> {
>> "pipeline": [
>>  “/path/to/tile.las",
>> {
>>   "type": "filters.range",
>>   "limits": "Classification[2:2]"
>> },
>> {
>>   "type": "writers.gdal",
>>   "resolution": 2.0,
>>   "radius": 2.5,
>>   "gdaldriver":"GTiff",
>>   "filename": “tile.tif",
>>   "output_type": "mean,idw,count"
>>   }
>>   ]
>> }
>> 
>> …and then:
>> gdal_translate ./tile.tif mean_tile.png -b 1 -ot Byte -of png -scale
>> gdal_translate ./tile.tif idw_tile.png -b 2 -ot Byte -of png -scale
>> gdal_translate ./tile.tif count_tile.png -b 3 -ot Byte -of png -scale
>> 
>> …which produced valid pngs which worked as expected - greyscale rasterised point data that a web browser could view.
>> 
>> The nearest pipeline I could think of to generate a single writers.gdal ‘band’ as a PNG was:
>> 
>> {
>> "pipeline": [
>>  “/path/to/tile.las",
>> {
>>   "type": "filters.range",
>>   "limits": "Classification[2:2]"
>> },
>> {
>>   "type": "writers.gdal",
>>   "resolution": 2.0,
>>   "radius": 2.5,
>>   "gdalopts":"ot=PNG",
>>   "gdalopts":"co=scale",
>>   "gdalopts":"ot=Byte",
>>   "gdalopts":"co=WRITE_METADATA_AS_TEXT=NO",
>>   "gdalopts":"co=b=1",
>>   "filename": “tile.png",
>>   "output_type": "idw"
>>   }
>>   ]
>> }
>> 
>> …but this made a really big PNG (2mb, as opposed to single band pngs using an intermediate geotiff at < 150k) which was not readable by anything on my MacOS machine.
>> 
>> I’d happily take pipelne corrections! Lots of guessing there, and also lots of not knowing all the GDAL tricks!
>> 
>> Anyway, at a pinch, going gtiff -> png is possible, maybe slower than the required purpose?
>> 
>> HTH
>> 
>> Adam
>> 
>> 
>> 
>>> On 10 Jul 2017, at 10:21 pm, Vladimir Sandoval <vladimir.sandoval at yandex.com> wrote:
>>> 
>>> Gents:
>>> I've run it with "all" bands and get a nice, huge PNG (grayscale and it's not doing the resize), that I can open and view in Opticks but nothing else.
>>> 
>>> On windoze, you can drag an image into Firefox, and it will display it. Firefox says it cannot display the image "because it contains errors".
>>> 
>>> 
>>> 
>>> 08.07.2017, 23:09, "Howard Butler" <howard at hobu.co>:
>>>> Vladimir,
>>>> 
>>>> You need to be specific about what you mean by "cannot view the PNG with Firefox...".
>>>> 
>>>> The output of writers.gdal with the configuration you've provided is a 2-band PNG. That's probably not what you are expecting. Presumably you will want a colorized PNG or something? In that case, write out only the idw band as a PNG, and then use a GDAL VRT plus a color interpretation to convert that to a PNG that would be viewable in a way you'd expect in Firefox.
>>>> 
>>>> Hope this helps,
>>>> 
>>>> Howard
>>>> 
>>>> 
>>>> On Jul 7, 2017, at 9:17 PM, Adam Steer <Adam.Steer at anu.edu.au> wrote:
>>>> 
>>>> HI Vladimir - can you check whether a PNG with just one ‘band’ (ie ‘max’ OR ‘idw’ but not both) works?
>>>> 
>>>> That’s all I can think of… I actually need to test this as well :) Next week…
>>>> 
>>>> Cheers
>>>> 
>>>> Adam
>>>> 
>>>> 
>>>> On 8 Jul 2017, at 3:18 am, Vladimir Sandoval <vladimir.sandoval at yandex.com> wrote:
>>>> 
>>>> Trying to make a PNG from a .laz file to display in Firefox.
>>>> 
>>>> {
>>>>  "pipeline":[
>>>>    "somefile.laz",
>>>>    {
>>>>     "type":"writers.gdal",
>>>>      "resolution": 1,
>>>>      "output_type":"idw",
>>>>      "output_type":"max",
>>>>       "gdalopts":"of=PNG,outsize=128 128",
>>>>       "gdalopts":"co=WRITE_METADATA_AS_TEXT=NO",
>>>>      "filename":"outputfile.png"
>>>>    }
>>>>  ]
>>>> }
>>>> 
>>>> The pipeline runs and produces a PNG. I cannot view the PNG with Firefox, MS Paint, or Windows Photo Viewer, HOWEVER, I can open it and view it in Opticks (https://sourceforge.net/projects/opticks/).
>>>> 
>>>> Opticks shows a single band grey scale image, probably representative of the original .laz.
>>>> 
>>>> Anything I'm doing wrong here producing the "corrupted" PNG?
>>>> _______________________________________________
>>>> pdal mailing list
>>>> pdal at lists.osgeo.org
>>>> https://lists.osgeo.org/mailman/listinfo/pdal
>>>> 
>>>> _______________________________________________
>>>> pdal mailing list
>>>> pdal at lists.osgeo.org
>>>> https://lists.osgeo.org/mailman/listinfo/pdal
>>>> 
>> 
>