Re: [png-mng-implement] performance degradation (500-fold) encoding very wide pngs

[Andy R. <and...@gm...>]

On Sun, Feb 8, 2015 at 5:41 PM, Glenn Randers-Pehrson <gl...@gm...>
wrote:

>
> I wanted to ask how much memory you had.  I cannot even read the tall tiff
> on my machine that has 4G of main memory.
>
>
@Glenn: I have 192 GB RAM (2 quad-core Xeon 3.47GHz CPUs).

On Sun, Feb 8, 2015 at 5:57 PM, John Bowler <
joh...@gm...> wrote:
>
>
> Meanwhile: Andy, can you provide a self-contained shell script to repro
> the problem?  We can easily install any necessary programs, but it takes
> rather a lot more time to work out how to use the programs.
>
>
@John, I use a batch file (windows box) and it's just a couple lines
(below). Using GDAL I first build a VRT (virtual raster table) from my
kajillion tiled tiffs, then I read the VRT to make the PNG and geotiff. The
geotiff doesn't experience the slowdown so I presume that's with PNG
generation.

But that leads me to another question. Do you want me to upload the TIFF
tiles too (about 10.5 GB for both flights)? my batch file (example from Jan
27 aerial) reads:

REM build virtual raster table (super fast)
gdalbuildvrt -srcnodata 0 -vrtnodata 0 Elwha_20150127_merged_ALL.vrt
ElwhaShore_20150127_ALL_RGBAvg_WGS84*.tif

REM huge geotiff for GIS (couple minutes)
gdal_translate -of Gtiff -co "COMPRESS=JPEG" -co "JPEG_QUALITY=90" -co
"TILED=YES" -co "PHOTOMETRIC=YCBCR" -co BLOCKYSIZE=256 -co BLOCKXSIZE=256
-co "TFW=YES" -b 1 -b 2 -b 3 Elwha_20150127_merged_ALL.vrt
Elwha_20150127_ALL_RGBAvg_WGS84.tif

REM huge PNG for gigapan (3 days)
gdal_translate -of png -co "ZLEVEL=1" Elwha_20150127_merged_ALL.vrt
Elwha_20150127_merged_ALL.png

-- 
Andy