IPA itself is a zip file. After the suffix is changed, decompress the file to view the resource files used in the application.
Here, we will not explain how to handle PNG image resources during xcode packaging.
A Python script is provided below
from struct import *from zlib import *import statimport sysimport osdef getNormalizedPNG(filename): pngheader = "\x89PNG\r\n\x1a\n" file = open(filename, "rb") oldPNG = file.read() file.close() if oldPNG[:8] != pngheader: return None newPNG = oldPNG[:8] chunkPos = len(newPNG) # For each chunk in the PNG file while chunkPos < len(oldPNG): # Reading chunk chunkLength = oldPNG[chunkPos:chunkPos+4] chunkLength = unpack(">L", chunkLength)[0] chunkType = oldPNG[chunkPos+4 : chunkPos+8] chunkData = oldPNG[chunkPos+8:chunkPos+8+chunkLength] chunkCRC = oldPNG[chunkPos+chunkLength+8:chunkPos+chunkLength+12] chunkCRC = unpack(">L", chunkCRC)[0] chunkPos += chunkLength + 12 # Parsing the header chunk if chunkType == "IHDR": width = unpack(">L", chunkData[0:4])[0] height = unpack(">L", chunkData[4:8])[0] # Parsing the image chunk if chunkType == "IDAT": try: # Uncompressing the image chunk bufSize = width * height * 4 + height chunkData = decompress( chunkData, -8, bufSize) except Exception, e: # The PNG image is normalized return None # Swapping red & blue bytes for each pixel newdata = "" for y in xrange(height): i = len(newdata) newdata += chunkData[i] for x in xrange(width): i = len(newdata) newdata += chunkData[i+2] newdata += chunkData[i+1] newdata += chunkData[i+0] newdata += chunkData[i+3] # Compressing the image chunk chunkData = newdata chunkData = compress( chunkData ) chunkLength = len( chunkData ) chunkCRC = crc32(chunkType) chunkCRC = crc32(chunkData, chunkCRC) chunkCRC = (chunkCRC + 0x100000000) % 0x100000000 # Removing CgBI chunk if chunkType != "CgBI": newPNG += pack(">L", chunkLength) newPNG += chunkType if chunkLength > 0: newPNG += chunkData newPNG += pack(">L", chunkCRC) # Stopping the PNG file parsing if chunkType == "IEND": break return newPNGdef updatePNG(filename): data = getNormalizedPNG(filename) if data != None: file = open(filename, "wb") file.write(data) file.close() return True return datadef getFiles(base): global _dirs global _pngs if base == ".": _dirs = [] _pngs = [] if base in _dirs: return files = os.listdir(base) for file in files: filepath = os.path.join(base, file) try: st = os.lstat(filepath) except os.error: continue if stat.S_ISDIR(st.st_mode): if not filepath in _dirs: getFiles(filepath) _dirs.append( filepath ) elif file[-4:].lower() == ".png": if not filepath in _pngs: _pngs.append( filepath ) if base == ".": return _dirs, _pngsprint "-----------------------------------"print " iPhone PNG Images Normalizer v1.0"print "-----------------------------------"print " "print "[+] Searching PNG files...",dirs, pngs = getFiles(".")print "ok"if len(pngs) == 0: print " " print "[!] Alert: There are no PNG files found. Move this python file to the folder that contains the PNG files to normalize." exit() print " "print " - %d PNG files were found at this folder (and subfolders)." % len(pngs)print " "while True: normalize = raw_input("[?] Do you want to normalize all images (Y/N)? ").lower() if len(normalize) > 0 and (normalize[0] == "y" or normalize[0] == "n"): breaknormalized = 0if normalize[0] == "y": for ipng in xrange(len(pngs)): perc = (float(ipng) / len(pngs)) * 100.0 print "%.2f%% %s" % (perc, pngs[ipng]) if updatePNG(pngs[ipng]): normalized += 1print " "print "[+] %d PNG files were normalized." % normalized
You can restore these image files to a normal PNG.