#3156: Cannot export GRASS raster map using r.out.png (crashes on windows)
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Reporter: spawley | Owner: grass-dev@…
Type: defect | Status: new
Priority: normal | Milestone: 7.0.7
Component: Raster | Version: 7.0.4
Resolution: | Keywords: r.out.png, wingrass, g.ppmtopng
CPU: x86-64 | Platform: MSWindows 7
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Changes (by wenzeslaus):
* keywords: r.out.png, wingrass => r.out.png, wingrass, g.ppmtopng
Comment:
Replying to [comment:12 neteler]:
> How about making it "simply" a Python wrapper around r.out.gdal with PNG
etc hardcoded?
That would solve only `r.out.png` not `g.ppmtopng` or PNG driver (if it is
broken (please test)).
Additionally, `r.out.gdal` and `r.out.png` outputs are not identical and
`r.out.png` always gave me a more expected output, for example
transparency works.
However, your suggestion makes sense. An alternative I used was `d.rast`.
That again gives different result - the pixels are resampled so that when
ns and ew resolutions don't match you get the right shape unlike with
`r.out.gdal` or `r.out.png` where you get the result stretched when viewed
without georeferencing.
The code for `d.rast` is below. AFAIU `r.out.gdal` would require setting
transparency; code for a simple but limited way to do that is attached
too. I'm thinking about adding some of these functions to the Python
library.
{{{
#!python
def set_rendering_environment(width, height, filename, transparent,
backgroud_color='ffffff', driver='cairo',
compression=None, env=None):
# if parameter not provided (but allow for empty dictionary)
if env is None:
env = os.environ
env['GRASS_RENDER_WIDTH'] = str(width)
env['GRASS_RENDER_HEIGHT'] = str(height)
env['GRASS_RENDER_IMMEDIATE'] = driver
env['GRASS_RENDER_BACKGROUNDCOLOR'] = backgroud_color
env['GRASS_RENDER_TRUECOLOR'] = "TRUE"
if transparent:
env['GRASS_RENDER_TRANSPARENT'] = "TRUE"
else:
env['GRASS_RENDER_TRANSPARENT'] = "FALSE"
if compression:
env['GRASS_RENDER_FILE_COMPRESSION'] = str(compression)
env['GRASS_RENDER_FILE'] = str(filename)
def get_region():
gregion_out = gs.read_command('g.region', flags='pg')
region = gs.parse_key_val(gregion_out, sep='=')
return {'east': float(region['e']), 'north': float(region['n']),
'west': float(region['w']), 'south': float(region['s']),
'rows': int(region['rows']), 'cols': int(region['cols']),
'nsres': float(region['nsres']),
'ewres': float(region['ewres'])}
region = get_region()
if region['nsres'] > region['ewres']:
# oversample in rows, do not loose columns
width = region['cols']
height = region['rows'] * (region['nsres'] / region['ewres'])
else:
# oversample in columns, do not loose rows
width = region['cols'] * (region['ewres'] / region['nsres'])
height = region['rows']
if 't' in routpng_flags:
transparent = True
else:
transparent = False
set_rendering_environment(width=width, height=height,
filename=output_file,
transparent=True, driver='cairo',
compression=compression)
}}}
{{{
#!python
try:
from PIL import Image
except ImportError:
gcore.warning(_("Cannot save transparency because"
" PIL library is missing."))
return
if rgb == 'white':
rgb = (255, 255, 255)
elif rgb == 'black':
rgb = (0, 0, 0)
img = Image.open(filename)
img = img.convert("RGBA")
old_data = img.getdata()
new_data =
for item in old_data:
if item[0] == rgb[0] and item[1] == rgb[1] and item[2] ==
rgb[2]:
new_data.append((255, 255, 255, 0))
else:
new_data.append(item)
img.putdata(new_data)
img.save(filename, "PNG")
}}}
A step further would be a `r.export.png` module which would, with whatever
backend, create a georeferenced PNG but in a SRS provided by the user.
--
Ticket URL: <https://trac.osgeo.org/grass/ticket/3156#comment:13>
GRASS GIS <https://grass.osgeo.org>
