从 SQLite 检索图像，“无效或不受支持的图像格式”答案

【问题标题】：Retrieving image from SQLite, “Invalid or Unsupported Image Format”从 SQLite 检索图像，“无效或不受支持的图像格式”
【发布时间】：2020-09-29 23:00:23
【问题描述】：

我正在使用 Cloud9 IDE，当我打开在 SQLite 中存储和检索的图像时，我得到一个 "Invalid or Unsupported Image Format"。当我将convertToBinaryData 文件输入到writeTofile 函数中时，就会检索到照片，所以这肯定与SQL 有关。

有人可以帮助正确格式化吗？

def convertToBinaryData(filename):
#Convert digital data to binary format
with open(path, 'rb') as file:
    blobData = file.read()
return blobData

def writeTofile(data, filename):
# Convert binary data to proper format and write it on Hard Disk
with open(filename, 'wb') as file:
    advert = file.write(data)

@app.route("/place", methods=["GET", "POST"])
@login_required
def place():
if request.method == "GET":
    return render_template("place.html")

if request.method == "POST":

我已经尝试了以下四个选项，但它们都不起作用。

'''Version 1'''
    placing = "INSERT INTO food (category, title, description, shipping, photo, county, area, post_time, UID) VALUES (?,?,?,?,?,?,?,CURRENT_TIMESTAMP,?)"
    ad_photo = convertToBinaryData(request.form.get("photo"))

    db.execute(placing, (session["user_id"], request.form.get("category"), request.form.get("title"), request.form.get("description"), request.form.getlist("option[]"), ad_photo, request.form.get("county"), request.form.get("area")))

    row = db.execute('SELECT photo FROM food')
    print (str(row[0]))
    writeTofile(row[0], "dan.jpg")

错误：file.write（数据） TypeError：需要一个类似字节的对象，而不是'dict'

'''Version 2'''
    placing = "INSERT INTO food (category, title, description, shipping, photo, county, area, post_time, UID) VALUES (?,?,?,?,?,?,?,CURRENT_TIMESTAMP,?)"
    ad_photo = convertToBinaryData(request.form.get("photo"))
    db.execute(placing, (session["user_id"], request.form.get("category"), request.form.get("title"), request.form.get("description"), request.form.getlist("option[]"), ad_photo, request.form.get("county"), request.form.get("area")))

    row = db.execute('SELECT photo FROM food')
    print (row[0])
    writeTofile(row[0], "dan.jpg")

错误：file.write（数据） TypeError：需要一个类似字节的对象，而不是'dict'

'''Version 3'''
    placing = "INSERT INTO food (UID, category, title, description, shipping, photo, county, area, post_time) VALUES (?,?,?,?,?,?,?,?,CURRENT_TIMESTAMP)"
    ad_photo = convertToBinaryData(request.form.get("photo"))
    db.execute(placing, (session["user_id"], request.form.get("category"), request.form.get("title"), request.form.get("description"), request.form.getlist("option[]"), ad_photo, request.form.get("county"), request.form.get("area")))

    row = db.execute('SELECT photo FROM food')
    print (str(row[0]))
    mystring = str(row[0])
    b = mystring.encode('utf-8')
    writeTofile(b, "dan.jpg")

错误：没有错误，但创建的 JPEG 是“无效或不受支持的图像格式”

'''Version 4'''
    sqliteConnection = sqlite3.connect('finance.db')
    cursor = sqliteConnection.cursor()

    placing = "INSERT INTO food (category, title, description, shipping, photo, county, area, post_time, UID) VALUES (?,?,?,?,?,?,?,CURRENT_TIMESTAMP,?)"
    ad_photo = convertToBinaryData(request.form.get("photo"))

    # Convert data into tuple format
    data_tuple = (request.form.get("category"), request.form.get("title"), request.form.get("description"), request.form.get("option[]"), ad_photo, request.form.get("county"), request.form.get("area"), session["user_id"])
    cursor.execute(placing, data_tuple)
    sqliteConnection.commit()
    print("Image and file inserted successfully as a BLOB into a table")

    cursor.execute("SELECT photo from food")
    record = cursor.fetchone()

    writeTofile(record, "dan.jpg")
    cursor.close()

错误：TypeError：需要一个类似字节的对象，而不是“元组”

【问题讨论】：

如果假设它是二进制 blob，那么将其转换为 utf8 是很奇怪的
当我写 row = db.execute('SELECT * FROM food') writeTofile(row[0], "dan.jpg") 时，我得到一个 TypeError: a bytes-like object is required, not 'dict' 错误，这就是为什么我认为它可能是括号以及为什么我尝试了 utf-8。
略读文档，看起来您应该使用fetchone() 方法从db.execute() 返回的游标中获取一行？然后从中获取适当的列值？我对python不是很熟悉。
是的，我和fetchall()都试过了，还是搞不明白。

标签： python-3.x sqlite binary blob

【解决方案1】：

好吧，在写下我所有的错误然后尝试完全不同的东西之后，我终于弄明白了。感谢您的共鸣板。

def place():
"""place an ad"""
if request.method == "GET":
    return render_template("place.html")

if request.method == "POST":

    sqliteConnection = sqlite3.connect('finance.db')
    cursor = sqliteConnection.cursor()

    placing = "INSERT INTO food (category, title, description, shipping, photo, county, area, post_time, uid) VALUES (?,?,?,?,?,?,?,CURRENT_TIMESTAMP,?)"
    ad_photo = convertToBinaryData(request.form.get("photo"))

    # Convert data into tuple format
    data_tuple = ((request.form.get("category"), request.form.get("title"), request.form.get("description"), request.form.get("option[]"), ad_photo, request.form.get("county"), request.form.get("area"), session["user_id"]))
    cursor.execute(placing, data_tuple)
    sqliteConnection.commit()
    print("Image and file inserted successfully as a BLOB into a table")

    sqliteConnection = sqlite3.connect('finance.db')
    cursor = sqliteConnection.cursor()
    query = cursor.execute("SELECT * FROM food ORDER BY post_time DESC LIMIT 1")

    for row in query:
        pic = row[4]
        writeTofile(pic, "dan.jpg")
    sqliteConnection.commit()
    cursor.close()

return render_template("placed.html")

【讨论】：