I cannot display a blob image from my mysql database due to an error with the BytesIO

Question

I have saved an image in mysql and I want to show it but an error occurred and I would like you to help me know where the error originates from.

def convertToBinaryData(self,filename):
    #convert digital data to bynary format
    with open(filename,'rb') as file:
        binaryData = file.read()
    return binaryData

def upload image (self):
    self.btn_Frame.filename = filedialog.askopenfilename(initialdir="C:/Users/dimitri/Pictures",title="seleccione el dibujo",filetypes=[("PNG files","*.png"),("JPG files","*.jpg")])

    self.my_image = Image.open(self.btn_Frame.filename)

    self.blobImage = self.convertToBinaryData(self.btn_Frame.filename)

    self.resize_image = self.my_image.resize((200,200),Image.ANTIALIAS)

    self.new_image = ImageTk.PhotoImage(self.resize_image)

    foto= Label(self.Predecir_Frame,image=self.new_image)
    foto.photo = self.new_image
    foto.grid(row=1,column=0,pady=10,padx=30,sticky=W)

def save_DB(self):
    if self.name_var.get()=="" or self.lastName_var.get()==""  
            messagebox.showerror("Error", "All fields are required !!!")
    else:   
        con = pymysql.connect(host="localhost", user="root",password="", database="postulantebd")
        cur = con.cursor()
        cur.execute("insert into postulantes values(%s, %s, %s, %s)",(
            self.name_var.get(),
            self.lastName_var.get(),
            self.txt_address.get('1.0', 'end-1c'),
            self.blobImage
            ))
            con.commit()
            self.v2()
            self.fetch_all()
            con.close()


def fetch_all(self):
    con = pymysql.connect(host="localhost", user="root",password="", database="postulantebd")
    cur = con.cursor()
    cur.execute("select * from postulantes")
    rows=cur.fetchall()

    if len(rows)!=0:
        self.tabla_postulante.delete(*self.tabla_postulante.get_children())
        for row in rows:
            self.tabla_postulante.insert('',END,values=row)
            con.commit()
    con.close()
        
def get_cursor(self,ev):
    cursor_row=self.tabla_postulante.focus()
    contents=self.tabla_postulante.item(cursor_row)
    row=contents['values']
    self.name_var.set(row[0]),
    self.lastName_var.set(row[1]),
    self.txt_address.delete('1.0', 'end-1c')
    self.txt_address.insert('end-1c',row[2]),
    self.blobImagen = row[3]
    readBlob=Image.open(io.BytesIO(self.blobImage))
    pic = ImageTk.PhotoImage(readBlob)
    foto = Label(self.Predecir_Frame,image=pic)
    foto.grid(row=1,column=0,pady=10,padx=30,sticky=W)

the error that appears is the following: in get_cursor readBlob=Image.open(io.BytesIO(self.blobImagen)) TypeError: a bytes-like object is required, not 'str'

I know it's long but I didn't know how to make a shorter example thanks for taking the time to read

Hi, thanks for answering, I don't know how to read English very well so I will answer what I understood. In the code do not use the CREATE TABLE statement, I am working with mysql and phpmyadmin and it is a table of 10 columns in which 9 of those columns are varchar type and the last column is longblob type. I checked in phpmyadmin and the file is stored in binary. — Dimitri Drivakis
– Dimitri Drivakis, Commented Jan 2, 2021 at 21:48

acw1668 · Accepted Answer · 2021-01-03 12:07:00Z

When you insert the binary blob data (the image) into self.tabla_postulante using insert(), it will be converted to string (something like b'...'). You can change the binary blob data into hex string before inserting into self.tabla_postulante:

for row in rows:
    blob = row[3].hex()
    self.table_postulante.insert("", "end", values=(row[0], row[1], row[2], blob))

Then when you retrieve the row from self.tabla_postulante, you can convert back the hex string to bytes using bytes.fromhex():

def get_cursor(self, ev):
    ...
    blobImage = bytes.fromhex(row[3])
    readBlob = Image.open(io.BytesIO(blobImage))
    pic = ImageTk.PhotoImage(readBlob)
    foto = Label(self.Predecir_Frame, image=self.pic)
    foto.grid(row=1, column=0, pady=10, padx=30, sticky=W)
    foto.image = pic  # keep a reference to avoid garbage collected

Note that it is better to create foto outside get_cursor() and update the image using foto.configure(image=pic) inside the function.

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