How to use Foxit PDF SDK in a Web application’s server side

In this tutorial, you’ll learn how to use Foxit PDF SDK in a Web application’s server side. Foxit PDF SDK supports Python, C#, and Java language for Web server development. The example in the current tutorial uses Python language to develop a simple web application demo.

Preparation for Web application

Install a version of Python in which Foxit PDF SDK is supported. The example in this article uses Python 3.8 on Windows.

Python virtual environment

1. Create a python viratual environment.

mkdir webappdemo
cd webappdemo
python -m venv .venv

2. Activate the environment.

.venv\Scripts\activate

3. Install Foxit PDF SDK and Third-party modules.

In this example, we used Flask, which is a lightweight web application framework based on Python. In the activated virtual environment, perform the following actions:

pip install FoxitPDFSDKPython3
pip install Flask

Rending a PDF Page by using Foxit PDF SDK

Create a python script file named app_demo.py. 

1. Importing Python modules and libraries.

# Description: This is a demo for Foxit PDF SDK for Python.
import io
# import flask class
from flask import Flask
from flask import send_file
# import Foxit PDF SDK for python
from FoxitPDFSDKPython3 import *

2. Create Flask app.

app = Flask(__name__)

3. Initialize SDK library.

def InitLibrary():
    # The parameter "sn" can be found in the "gsdk_sn.txt" (the string after "SN=") and the "key" can be found in the "gsdk_key.txt" (the string after "Sign=").
    sn = ""
    key = ""
 
    # Initialize library
    error_code = Library.Initialize(sn, key)
    if error_code != e_ErrSuccess:
        print("Library Initialize Error: {}".format(error_code))
        return False
    print("Library Initialize Success")
    return True
# Initialize library
is_library_init = InitLibrary()

4. Define MemoryStream callback class.

class MemoryStream(StreamCallback):
    def __init__(self, *args):
        super().__init__()
        self.buffer_ = bytearray(b'')
        self.ref_ = 0
 
    def __del__(self):
        self.__disown__()
 
    def Retain(self, *args):
        self.ref_ += 1
        return self
 
    def IsEOF(self, *args):
        return True
 
    def GetPosition(self, *args):
        pass
 
    def Release(self, *args):
        self.ref_ -= 1
 
    def GetSize(self, *args):
        pass
 
    def Flush(self, *args):
        return True
 
    def ReadBlock(self, *args):
        pass
 
    def WriteBlock(self, *args):
        if args[0] is not None:        
            self.buffer_[args[0][1]:args[0][1]] = bytearray(args[0][0])
            return True
        else:
            return False

5. Rending a PDF page.

def WebDemo():
    path = "D:/AboutFoxit.pdf"
    # Load the document
    doc = PDFDoc(path)
    if e_ErrSuccess != doc.Load(""):
        return None
    page_count = doc.GetPageCount()
    print("Page Count: {}".format(page_count))
    page = doc.GetPage(0)
    # Parse the page
    page.StartParse(PDFPage.e_ParsePageNormal, None, False)
 
    # Prepare a bitmap for rendering.
    page_width = page.GetWidth()
    page_height = page.GetHeight()
    width = int(page_width)
    height = int(page_height)
    rectf = RectF(0.5, 0.5, width, height)
    bitmap_width = int(rectf.Width())
    bitmap_height = int(rectf.Height())
    bitmap = Bitmap(bitmap_width, bitmap_height, Bitmap.e_DIBArgb)   
    render = Renderer(bitmap, False)
    matrix = page.GetDisplayMatrix(0, 0, width, height, 0)
    bitmap.FillRect(0xFFFFFFFF, None)
    # render page to bitmap
    render.StartRender(page, matrix, None)
    image = Image()
    image.AddFrame(bitmap)
    stream = MemoryStream()
    # save bitmap to stream
    image.SaveAs(stream, ".png")
    # return image buffer
    return stream.buffer_

6. Release SDK library.

@app.teardown_appcontext
def teardown_appcontext(exception):
    print("teardown_appcontext")
    Library.Release()

7. Add Flask routing mapping.

# @app.route("/") maps the root path ("/") to the web_demo function
@app.route("/")
def web_demo():
    if not is_library_init:
        return "<p>Library Initialize Error</p>"
    image_buff = WebDemo()
    if image_buff is not None:
        image_io = io.BytesIO(image_buff)
        image_io.seek(0)
        return send_file(image_io, mimetype='image/png')
    else:
        return "<p>Error</p>"

Start Web Application server

Starting the service requires ensuring that it is under the creation of a Python virtual environment.

cd webappdemo
flask --app app_demo run

Open http://127.0.0.1:5000 in your browser to access the web app demo and  the window is shown as follows.