[gdal-dev] convert USGS Topo GeoPDF to GeoTiff, file size

[Liu, Jian]

Hello,

I try to use GDAL to convert USGS Topo geopdfs to Geotiff format. I have the following command:

gdalwarp geo.pdf geo.tif -crop_to_cutline -cutline C:\JIANTestFolder\cutline.csv -overwrite --config GDAL_CACHEMAX 500 -wm 500 --config GDAL_PDF_LAYERS_OFF Projection_and_Grids --config GDAL_PDF_DPI 508 -co "TILED=YES" -co "TFW=YES" -co "COMPRESS=JPEG" -co "PHOTOMETRIC=YCBCR"

I want to maintain the image quality while keeping the file to a minimal size. But my output .tif is about twice as big as the input pdf (19.5M vs. 11.9M)  -- the output dpi (GDAL_PDF_DPI=508) is set based on the metadata information in the geopdf. I read somewhere that pdf just stores image "as it is", and I am wondering how come my geotiff is twice as big, even with the jpeg compression with the YCBCR option? Is it still possible to reduce its size?

Here is the geopdf I use:    http://ims.er.usgs.gov/gda_services/download?item_id=5998960

I've searched the mail archive and couldn't find anything relevant. I appreciate any answers or suggestions about converting geopdf to geotiffs. Thank you!

Best regards,
Jian


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