Saving an Image Passed to the Server Using Phonegap

       2/19/2013        Mobile Development , PhoneGap , Ruby On Rails

Specifications

  • Website with Ruby on Rails (Rails version 3.2.6)
  • Mobile Application Developed with PhoneGap (version 2.4.0)

Scenario

The mobile application needs to pass an image captured from the mobile device towards the website. The website then needs to save it for displaying purposes.

The camera.getPicture function, which is available on PhoneGap, opens the device's default camera so that the user can take a picture. By default, this function returns a string containing Base64 encoded image data.

Application to the Code

Using the Base64 encoded data, we can send this information to the server using an AJAX function and submitting the image data as a key-value pair.

Submitting to the server via AJAX might look similar to this code:

$.ajax({
 type: "POST",
 url: [REPLACE WITH URL TO WHERE THE REQUEST SHOULD BE SENT],
 data: {
  imgData: [REPLACE WITH THE BASE64-IMAGE-DATA]
 },
 dataType: "text",
 timeout: 10000
}).fail(function(jqXHR, status) {
 // do some checking here
}).done(function(jqxHR, status){
 // do some checking here
});

On the server side, you can catch this data and do the process of saving of an image. See code below as an example:

Controller
def upload_image
  
 # this is to verify if the correct 
 if params[:imgData] && !params[:imgData].blank
  ImageHandler.save_image(params[:imgData])
  result = {:message => "Image Saved", :save_status => 0}
 else
  result = {:message => "Data is invalid", :save_status => 1}
 end
  
 respond_to do |format|
  format.xml { render xml: result}
  format.json { render json: result}
 end
 
end

Model (app/assets/models/image_handler.rb)
class ImageHandler < ActiveRecord::Base
  def save_image(imgData)
 directory = "public/data/"
 
 if !File.exists?(directory)
  Dir.mkdir(directory)
 end
 
 path = File.join(directory, "image.png")
 File.open(path, 'wb') do|f|
  f.write(Base64.decode64(imgData))
 end
  end
end
Data sent over AJAX will be handled on the controller. In the controller, we check whether the imgData are sent. If yes, pass the imgData to the model and do the saving process else, we need to return an error message.

For the model, the imgData passed would be decoded and written as file inside the public/data directory. This way, the data can now be displayed as a normal image for websites using the imgage_tag by rails or just by using a simple image tags in HTML.

As for the mobile application, an XML result will be sent back for checking whether the process is done successfully.



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