[gdal-dev] Set a PNG background transparent without flip

[liglio.pessoal at nexxa.com.br]

Hi,

 

I want to set an image PNG background to transparent. I do using gdalwarp,
but the image flips horizontally. 

I am using a workaround, executing the gdalwarp command twice to flip back.

Can I set the background to transparent using just one command without flip
?

 

IMAGE ORIGINAL:

Driver: PNG/Portable Network Graphics

Files: 2022-09-25--18_46_27.png

Size is 400, 400

Metadata:

  NODATA_VALUES=0 0 0

Image Structure Metadata:

  INTERLEAVE=PIXEL

Corner Coordinates:

Upper Left  (    0.0,    0.0)

Lower Left  (    0.0,  400.0)

Upper Right (  400.0,    0.0)

Lower Right (  400.0,  400.0)

Center      (  200.0,  200.0)

Band 1 Block=400x1 Type=Byte, ColorInterp=Red

  NoData Value=0

  Mask Flags: PER_DATASET NODATA

Band 2 Block=400x1 Type=Byte, ColorInterp=Green

  NoData Value=0

  Mask Flags: PER_DATASET NODATA

Band 3 Block=400x1 Type=Byte, ColorInterp=Blue

  NoData Value=0

  Mask Flags: PER_DATASET NODATA

 

COMMAND:

gdalwarp -of PNG -overwrite  -srcnodata 0 -dstalpha -to
SRC_METHOD=NO_GEOTRANSFORM 2022-09-25--18_56_15.png
MI-2022-09-25--18_56_15.png

 

IMAGE MODIFIED (Background transparent and flipped)

Driver: PNG/Portable Network Graphics

Files: MI-2022-09-25--18_46_27.png

       MI-2022-09-25--18_46_27.png.aux.xml

Size is 400, 400

Origin = (0.000000000000000,400.000000000000000)

Pixel Size = (1.000000000000000,-1.000000000000000)

Image Structure Metadata:

  INTERLEAVE=PIXEL

Corner Coordinates:

Upper Left  (       0.000,     400.000)

Lower Left  (   0.0000000,   0.0000000)

Upper Right (     400.000,     400.000)

Lower Right (     400.000,       0.000)

Center      (     200.000,     200.000)

Band 1 Block=400x1 Type=Byte, ColorInterp=Red

  Mask Flags: PER_DATASET ALPHA

Band 2 Block=400x1 Type=Byte, ColorInterp=Green

  Mask Flags: PER_DATASET ALPHA

Band 3 Block=400x1 Type=Byte, ColorInterp=Blue

  Mask Flags: PER_DATASET ALPHA

Band 4 Block=400x1 Type=Byte, ColorInterp=Alpha

 

Regards,

Liglio

 

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