Functioning Bitmap to ASCII Art Converter WIP

file = open(input("Please enter the file location of a 24 bit colour depth bitmap image ")+".bmp","rb").read()

allbytes = []
filecontent = []

for line in file:
    allbytes.append(str(hex(line)[2:]))

#Metadata converted to denary and stored as variables
offset = int((allbytes[13]+allbytes[12]+allbytes[11]+allbytes[10]),16)
width = int((allbytes[21]+allbytes[20]+allbytes[19]+allbytes[18]),16)
height = int((allbytes[25]+allbytes[24]+allbytes[23]+allbytes[22]),16)
depth = int((allbytes[29]+allbytes[28]),16)

print("Offset from 0 to image pixel data:",offset)
print("Width:",width)
print("Height:",height)
print("Bit depth:",depth)

#Puts the pixel data in reverse order to compensate for the fact that bitmaps are printed from the bottom right rather than top left.
allbytes.reverse()

#Pixel data isolated, stored as list
for index in range(len(allbytes)):
    filecontent.append(allbytes[index])

#Clears variable allbytes to save memory
del allbytes

#Breaks up the pixel data into an array, list of RGB values within a list of pixels
pixelmap = []
currpixel = []
for index, entry in enumerate(filecontent):
    currpixel.append(entry)
    if index % 3 == 0:
        pixelmap.append(currpixel)
        currpixel = []

#Assessing the brightness/darkness of each pixel

#black (0) = #
#dark (63) = £
#medium (126) = *
#light (189) = ~
#white (255) = " "

asciiart = []

for pixel in pixelmap:

    total = 0

    for rgb in pixel:
        total += int(rgb,16)

    if (total / 3) >= 254:
        char = " "
    elif (total / 3) >= 189:
        char = "~"
    elif (total / 3) >= 126:
        char = "*"
    elif (total / 3) >= 63:
        char = "£"
    elif (total / 3) >= 0:
        char = "#"

    asciiart.append(char)

#Clears variable pixelmap to save memory
del pixelmap

textfile = open(input("Enter a file name for your converted ASCII art image ")+".txt","w")

#Printing the converted image
line = ""
for index, pixel in enumerate(asciiart):
    line = pixel+line
    if index % width == 0:
        textfile.write(line+"\n")
        line = ""
textfile.close()