A simple script to create lower-resolution Android drawables from higher-resolution ones.

drawable_convert.py

#!/usr/bin/python

import sys
import argparse
import os
import re

'''
A simple script to create lower-resolution Android drawables from higher-resolution ones.

For example, given a batch of -xhdpi images, you can generate -hdpi and -mdpi images.

This makes it possible to only export highest-resolution artwork from image authoring tools, and
automate the rest.

Usage:

   drawable_convert.py -d res/drawable-mdpi -d res/drawable-hdpi res/drawable-xhdpi-v14/select*.png
   
   ... will take select*.png from xhdpi and place versions into mdpi and hdpi folders.
   
   Correct resize ratios are computed based on resource directory names.
   
   Actual scaling is done by ImageMagick's convert command.
'''

class Converter:
	def __init__(self, dstList):
		print u'Dst list: {0}'.format(dstList)
		self.mDstList = dstList
		
	def convert(self, src):
		for dstpath in self.mDstList:
			(srcpath, srcname) = os.path.split(src)
			dst = os.path.join(dstpath, srcname)
			self.convertOne(src, dst)

	def convertOne(self, src, dst):
		print u'\n*****\n{0} to {1}\n*****\n'.format(src, dst)
		'''
		Determine relative density
		'''
		srcDpi = self.getDpi(src)
		dstDpi = self.getDpi(dst)
		
		if srcDpi < dstDpi:
			print u'NOT converting from {0}dpi to {1}dpi'.format(srcDpi, dstDpi)
		else:
			factor = dstDpi*100/srcDpi
			print u'Converting from {0}dpi to {1}dpi, {2}%'.format(srcDpi, dstDpi, factor)
			cmd = u'convert -verbose "{0}" -resize "{2}%x{2}%" "{1}"'.format(src, dst, factor)
			os.system(cmd)
		
	def getDpi(self, f):
		p = os.path.dirname(f)
		if re.match('.*drawable.*\\-mdpi.*', p):
			return 160
		elif re.match('.*drawable.*\\-hdpi.*', p):
			return 240
		elif re.match('.*drawable.*\\-xhdpi.*', p):
			return 320
		else:
			raise ValueError(u'Cannot determine densitiy for {0}'.format(p))

if __name__ == "__main__":
	'''
	Parse command line arguments
	'''
	parser = argparse.ArgumentParser(description='Converts drawable resources in Android applications')
	parser.add_argument('-d', dest='DST', action='append', required=True, help='destination directory')
	parser.add_argument('src', nargs='+', help='files to convert (one or more)')
	args = parser.parse_args()

	cv = Converter(args.DST)
	for src in args.src:
		cv.convert(src)


'''


if [ $# -lt 1 ] ; then
	echo "Usage: $0 file_list"
	exit 1
fi

for f in $*
do
	echo "File: ${f}"
	convert -verbose "${f}" -resize "75%x75%" "../drawable-hdpi/${f}"
	convert -verbose "${f}" -resize "50%x50%" "../drawable-mdpi/${f}"
done

'''

For even higher resolutions add around line 61:

    elif re.match('.*drawable.*\\-xxhdpi.*', p):
        return 480
    elif re.match('.*drawable.*\\-xxxhdpi.*', p):
        return 640

I recommend changing 100 to 100.0 in line 49, like so

factor = dstDpi*100.0/srcDpi

Otherwise, converting xxxhdpi to hdpi results in 37% instead of 37.5%, or a launcher icon of 71x71 instead of 72x72.

First let me clear that i don't know anything about python but i want to know that how this script will work and how we will do smart work and get help. I have installed python and setup its path also. I have created some of the simple project and run also and its working fine. Now how to run this python script because when i create file using above script and try to run, it will send me some error. i have run below command to run this script. I think i am missing project file location on that python script.

.../User>python Converter.py -d res/drawable-mdpi -d res/drawable-hdpi res/drawable-xhdpi-v14/select*.png