Nik, No, the PNG format does not support direct creation, only creation by copying an existing dataset (GDALCreateCopy()). You can interactively see the capabilities of a driver like this:
gdalinfo --format png Format Details: Short Name: PNG Long Name: Portable Network Graphics Extension: png Mime Type: image/png Help Topic: frmt_various.html#PNG Supports: CreateCopy() - Create dataset by copying another. Supports: Virtual IO - eg. /vsimem/ Creation Datatypes: Byte UInt16 <CreationOptionList> <Option name="WORLDFILE" type="boolean" description="Create world file" /> <Option name="ZLEVEL" type="int" description="DEFLATE compression level 1-9" default="6" /> </CreationOptionList> The "Supports: CreateCopy()" means you can create the format, but only by copying an existing dataset. Formats supporting creation will have "Supports: Create()". You can get a broad listing of all formats like this: gdalinfo --formats .... SDTS (rov): SDTS Raster DTED (rwv): DTED Elevation Raster PNG (rwv): Portable Network Graphics JPEG (rwv): JPEG JFIF MEM (rw+): In Memory Raster ... The "w" means it supports at least CreateCopy(). The "+" means it supports create+update. Best regards, On Tue, Jul 16, 2013 at 10:14 PM, Nik Sands <[email protected]> wrote: > Can I use GDALCreate to create (and later write to) PNG images? > If so, is "PNG" the correct string for GDALGetDriverByName? > > Otherwise, can somebody please let me know why the code below returns NULL > from GDALCreate (assigned to dstDS)? > > Advice much appreciated, as always. > > Thanks, > Nik. > > > > GDALDriverH hDriver = GDALGetDriverByName("PNG"); > char **papszOptions = NULL; > > papszOptions = CSLSetNameValue( papszOptions, "WORLDFILE", "NO" ); > papszOptions = CSLSetNameValue( papszOptions, "ZLEVEL", "9" ); > > GDALDatasetH dstDS = GDALCreate( hDriver, "/var/tmp/image.png", > 256, 256, 4, GDT_Float32, papszOptions ); > _______________________________________________ > gdal-dev mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/gdal-dev > -- ---------------------------------------+-------------------------------------- I set the clouds in motion - turn up | Frank Warmerdam, [email protected] light and sound - activate the windows | http://pobox.com/~warmerdam and watch the world go round - Rush | Geospatial Software Developer
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