[gdal-dev] Re: warp, translate and world files

[Paul Meems]

Hermann,

You're right the size difference is because of PNG8 or PNG24.

I'm now on the gdal_warp track again. But I can't produce a PNG file. When I
use -ot PNG I get this list of supported file formats:
  VRT: Virtual Raster
  GTiff: GeoTIFF
  NITF: National Imagery Transmission Format
  HFA: Erdas Imagine Images (.img)
  ELAS: ELAS
  MEM: In Memory Raster
  BMP: MS Windows Device Independent Bitmap
  PCIDSK: PCIDSK Database File
  ILWIS: ILWIS Raster Map
  SGI: SGI Image File Format 1.0
  Leveller: Leveller heightfield
  Terragen: Terragen heightfield
  ERS: ERMapper .ers Labelled
  JP2ECW: ERMapper JPEG2000
  RMF: Raster Matrix Format
  RST: Idrisi Raster A.1
  INGR: Intergraph Raster
  GSBG: Golden Software Binary Grid (.grd)
  PNM: Portable Pixmap Format (netpbm)
  ENVI: ENVI .hdr Labelled
  EHdr: ESRI .hdr Labelled
  PAux: PCI .aux Labelled
  MFF: Vexcel MFF Raster
  MFF2: Vexcel MFF2 (HKV) Raster
  BT: VTP .bt (Binary Terrain) 1.3 Format
  IDA: Image Data and Analysis
  ADRG: ARC Digitized Raster Graphics
  SAGA: SAGA GIS Binary Grid (.sdat)

Does this mean I haven't build my GDAL properly? If not can you give me a
hint on how to enable png support in the make files?

Thanks,

Paul


2010/10/26 Hermann Peifer <peifer at gmx.eu>

> On 25/10/2010 11:17, Paul Meems wrote:
>
>> Hi list,
>>
>> I've got several png files with worldfiles.
>> I need them in another projection (28992 --> 3785).
>> I'm using gdalwarp to reproject to a tiff file and then I use
>> gdal_translate to create a png file again.
>> My original png file is about 25 kB, the warped tiff is over 2MB and the
>> translated png file is over 80 kB.
>>
>>
> I am not quite sure why you don't use -of png to save the creation of the
> intermediate tiff file. You might also be able to use -of byte which creates
> an 8 bit PNG (if this format is sufficient for your purpose).
>
> The size difference 20k vs 80k could be due to the fact that the source
> file is PNG8 and the generated file is PNG24. There may be other reasons,
> though.
>
> Hermann
>
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