dash/contrib/devtools/optimize-pngs.py

#!/usr/bin/env python

import os
import sys
import subprocess
import hashlib
from PIL import Image

def file_hash(filename):
    '''Return hash of raw file contents'''
    with open(filename, 'rb') as f:
        return hashlib.sha256(f.read()).hexdigest()

def content_hash(filename):
    '''Return hash of RGBA contents of image'''
    i = Image.open(filename)
    i = i.convert('RGBA')
    data = i.tostring()
    return hashlib.sha256(data).hexdigest()

#optimize png, remove various color profiles, remove ancillary chunks (alla) and text chunks (text)
#pngcrush -brute -ow -rem gAMA -rem cHRM -rem iCCP -rem sRGB -rem alla -rem text

pngcrush = 'pngcrush'
git = 'git'
folders = ["src/qt/res/movies", "src/qt/res/icons", "src/qt/res/images"]
basePath = subprocess.check_output([git, 'rev-parse', '--show-toplevel']).rstrip('\n')
totalSaveBytes = 0

outputArray = []
for folder in folders:
    absFolder=os.path.join(basePath, folder)
    for file in os.listdir(absFolder):
        extension = os.path.splitext(file)[1]
        if extension.lower() == '.png':
            print("optimizing "+file+"..."),
            file_path = os.path.join(absFolder, file)
            fileMetaMap = {'file' : file, 'osize': os.path.getsize(file_path), 'sha256Old' : file_hash(file_path)};
            fileMetaMap['contentHashPre'] = content_hash(file_path)
        
            pngCrushOutput = ""
            try:
                pngCrushOutput = subprocess.check_output(
                        [pngcrush, "-brute", "-ow", "-rem", "gAMA", "-rem", "cHRM", "-rem", "iCCP", "-rem", "sRGB", "-rem", "alla", "-rem", "text", file_path],
                        stderr=subprocess.STDOUT).rstrip('\n')
            except:
                print "pngcrush is not installed, aborting..."
                sys.exit(0)
        
            #verify
            if "Not a PNG file" in subprocess.check_output([pngcrush, "-n", "-v", file_path], stderr=subprocess.STDOUT):
                print "PNG file "+file+" is corrupted after crushing, check out pngcursh version"
                sys.exit(1)
            
            fileMetaMap['sha256New'] = file_hash(file_path)
            fileMetaMap['contentHashPost'] = content_hash(file_path)

            if fileMetaMap['contentHashPre'] != fileMetaMap['contentHashPost']:
                print "Image contents of PNG file "+file+" before and after crushing don't match"
                sys.exit(1)

            fileMetaMap['psize'] = os.path.getsize(file_path)
            outputArray.append(fileMetaMap)
            print("done\n"),

print "summary:\n+++++++++++++++++"
for fileDict in outputArray:
    oldHash = fileDict['sha256Old']
    newHash = fileDict['sha256New']
    totalSaveBytes += fileDict['osize'] - fileDict['psize']
    print fileDict['file']+"\n  size diff from: "+str(fileDict['osize'])+" to: "+str(fileDict['psize'])+"\n  old sha256: "+oldHash+"\n  new sha256: "+newHash+"\n"
    
print "completed. Total reduction: "+str(totalSaveBytes)+" bytes"