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#!/usr/bin/env python3
# ******************************************************************************
#
# Name: rgb2pct
# Project: GDAL Python Interface
# Purpose: Application for converting an RGB image to a pseudocolored image.
# Author: Frank Warmerdam, warmerdam@pobox.com
#
# ******************************************************************************
# Copyright (c) 2001, Frank Warmerdam
# Copyright (c) 2020-2021, Idan Miara <idan@miara.com>
#
# SPDX-License-Identifier: MIT
# ******************************************************************************
import os.path
import sys
import textwrap
from typing import Optional
from osgeo import gdal
from osgeo_utils.auxiliary.base import PathLikeOrStr
from osgeo_utils.auxiliary.color_table import get_color_table
from osgeo_utils.auxiliary.gdal_argparse import GDALArgumentParser, GDALScript
from osgeo_utils.auxiliary.util import (
GetOutputDriverFor,
enable_gdal_exceptions,
open_ds,
)
@enable_gdal_exceptions
def rgb2pct(
src_filename: PathLikeOrStr,
pct_filename: Optional[PathLikeOrStr] = None,
dst_filename: Optional[PathLikeOrStr] = None,
color_count: int = 256,
driver_name: Optional[str] = None,
creation_options: Optional[list] = None,
):
# Open source file
src_ds = open_ds(src_filename)
if src_ds is None:
raise Exception(f"Unable to open {src_filename}")
if src_ds.RasterCount < 3:
raise Exception(
f"{src_filename} has {src_ds.RasterCount} band(s), need 3 for inputs red, green and blue."
)
# Ensure we recognise the driver.
if not driver_name:
driver_name = GetOutputDriverFor(dst_filename)
dst_driver = gdal.GetDriverByName(driver_name)
if dst_driver is None:
raise Exception(f'"{driver_name}" driver not registered.')
# Generate palette
if pct_filename is None:
ct = gdal.ColorTable()
err = gdal.ComputeMedianCutPCT(
src_ds.GetRasterBand(1),
src_ds.GetRasterBand(2),
src_ds.GetRasterBand(3),
color_count,
ct,
callback=gdal.TermProgress_nocb,
)
else:
ct = get_color_table(pct_filename)
# Create the working file. We have to use TIFF since there are few formats
# that allow setting the color table after creation.
if driver_name.lower() == "gtiff":
tif_filename = dst_filename
else:
import tempfile
tif_filedesc, tif_filename = tempfile.mkstemp(suffix=".tif")
gtiff_driver = gdal.GetDriverByName("GTiff")
# Convert options to list
if isinstance(creation_options, str):
creation_options = creation_options.split()
if not creation_options:
creation_options = []
tif_ds = gtiff_driver.Create(
tif_filename,
src_ds.RasterXSize,
src_ds.RasterYSize,
1,
options=creation_options,
)
tif_ds.GetRasterBand(1).SetRasterColorTable(ct)
# ----------------------------------------------------------------------------
# We should copy projection information and so forth at this point.
tif_ds.SetProjection(src_ds.GetProjection())
tif_ds.SetGeoTransform(src_ds.GetGeoTransform())
if src_ds.GetGCPCount() > 0:
tif_ds.SetGCPs(src_ds.GetGCPs(), src_ds.GetGCPProjection())
# ----------------------------------------------------------------------------
# Actually transfer and dither the data.
err = gdal.DitherRGB2PCT(
src_ds.GetRasterBand(1),
src_ds.GetRasterBand(2),
src_ds.GetRasterBand(3),
tif_ds.GetRasterBand(1),
ct,
callback=gdal.TermProgress_nocb,
)
if err != gdal.CE_None:
raise Exception("DitherRGB2PCT failed")
if tif_filename == dst_filename:
dst_ds = tif_ds
else:
dst_ds = dst_driver.CreateCopy(dst_filename or "", tif_ds)
tif_ds = None
os.close(tif_filedesc)
gtiff_driver.Delete(tif_filename)
return dst_ds
def doit(**kwargs):
try:
ds = rgb2pct(**kwargs)
return ds, 0
except Exception:
return None, 1
class RGB2PCT(GDALScript):
def __init__(self):
super().__init__()
self.title = "Convert a 24bit RGB image to 8bit paletted image"
self.description = textwrap.dedent(
"""\
This utility will compute an optimal pseudo-color table for a given RGB image
using a median cut algorithm on a downsampled RGB histogram.
Then it converts the image into a pseudo-colored image using the color table.
This conversion utilizes Floyd-Steinberg dithering (error diffusion)
to maximize output image visual quality."""
)
def get_parser(self, argv) -> GDALArgumentParser:
parser = self.parser
parser.add_argument(
"-of",
dest="driver_name",
metavar="gdal_format",
help="Select the output format. "
"if not specified, the format is guessed from the extension. "
"Use the short format name.",
)
group = parser.add_mutually_exclusive_group()
group.add_argument(
"-n",
dest="color_count",
type=int,
default=256,
metavar="color",
choices=tuple(range(2, 257)),
help="Select the number of colors in the generated color table. "
"Defaults to 256. Must be between 2 and 256.",
)
group.add_argument(
"-pct",
dest="pct_filename",
type=str,
help="Extract the color table from <palette_file> instead of computing it. "
"Can be used to have a consistent color table for multiple files. "
"The palette file must be either a raster file in a GDAL supported format with a "
"palette or a color file in a supported format (txt, qml, qlr).",
)
parser.add_argument(
"--creation-option",
"--co",
dest="creation_options",
default=[],
action="append",
help="GeoTIFF creation options, e.g. COMPRESS=LZW",
)
parser.add_argument("src_filename", type=str, help="The input RGB file.")
parser.add_argument(
"dst_filename",
type=str,
help="The output pseudo-colored file that will be created.",
)
return parser
def doit(self, **kwargs):
return rgb2pct(**kwargs)
def main(argv=sys.argv):
return RGB2PCT().main(argv)
if __name__ == "__main__":
sys.exit(main(sys.argv))
|
