def METHOD_NAME(folder):
    files = [] #list of image filenames
    dirFiles = os.listdir(folder) #list of directory files
    dirFiles.sort() #good initial sort but doesnt sort numerically very well
    sorted(dirFiles) #sort numerically in ascending order
    for filename in dirFiles: #filter out all non jpgs
        if '.png' in filename:
            files.append(filename)
    return files