HOW TO SEND IMAGE TO A REST API, FLASK

send_image_post.py

# DEMO CLASS
class PlotTimeSeries: 
    def __init__(self):
        pass
    def _find_weekend_indices(self, datetime_array, weekend=5):
        """
        Returns all indices of Saturdays & Sundays in a datetime array
        datetime_array(pandas) = pandas datetime array
        weekend(int) = assume weekend starts at day=5=Saturday
        """
        #empty list to tore indeces
        indices = []


        for i in range(len(datetime_array)):
            #  get day of the week with Monday=0, Saturday=5, Sunday=6
            if datetime_array[i].weekday() >= weekend:
                indices.append(i)

        return indices
    
    def _highlight_datetimes(self, indices, ax, df, facecolor='green', alpha_span=0.2):
        """
        Highlights all weekends in an axes object
        indices(list) = list of Saturdays and Sundays indeces corresponding to dataframe
        ax(matplot) = pyplot object
        df(pandas) = pandas dataframe
        """
        i = 0
        #iterate over indeces
        while i < len(indices)-1:
            #highlight from i to i+1
            ax.axvspan(df.index[indices[i]], 
                       df.index[indices[i] + 1], 
                       facecolor=facecolor, 
                       edgecolor='none', 
                       alpha=alpha_span)
            i += 1
            
    def plot(self, df, dfs_dict, title="Comments Sentiment Timeline"):
        
        fig, axes = plt.subplots(nrows=1, ncols=1, sharex=True,figsize=(13,5))
                
        for k_name, v_df in dfs_dict.items():
            if k_name == "positive":
                marker = "^"
                color = "green"
                label = "Positive Sentiment"
                
            if k_name == "nevative":
                marker = "v"
                color = "red"
                label = "Negative Sentiment"
                
            if k_name == "neutral":
                marker = "o"
                color = "blue"
                label = "Neutral sentiment"
                
            if k_name == "mixed":
                
                marker = "|"
                color = "black"
                label = "Mixed sentiment"
                
            #draw all columns of dataframe
            axes.plot(v_df.index, v_df, marker=marker, color = color, label=label, alpha=.8)

        
        #find weekend indeces
        weekend_indices = self._find_weekend_indices(df.index, weekend=5)
        #highlight weekends
        self._highlight_datetimes(weekend_indices, axes, df, "green")

        #set title and y label
        axes.set_title(title, fontsize=12)
        axes.set_ylabel("Sentiment Counts")
        axes.legend()
        plt.tight_layout()

        #add xaxis gridlines
        axes.xaxis.grid(b=True, which='major', color='black', linestyle='--', alpha=1)

        # here is the trick save your figure into a bytes object and you can afterwards expose it via flas
        bytes_image = io.BytesIO()
        plt.savefig(bytes_image, format='png')
        bytes_image.seek(0)
        
        return bytes_image
      
# INSTANCEs
plot_timeline = PlotTimeSeries()
sampler_df = SampleDataframe()
      

# FLASK DEMO ENDPOINT
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@app.route("/sentiment_plot", methods=['GET'])
def plot_sentiment():
    if request.method == 'GET':

        print( request.args)
        fbPageId = request.args.get('fbPageId')
        limit = int(request.args.get('limit'))

        print(fbPageId)

        df = read_comments(client, fbPageId=fbPageId, limit = limit )

        df_dt, positive, negative, neutral, mixed = sampler_df.get_df_datetime(df, time_split='2020-02-01 00:00:00')
        
        # return dict
        sampled_df = sampler_df.sample( positive, negative, neutral, mixed, sample_frec=f'{24*60}min')

        bytes_obj = plot_timeline.plot(df_dt, sampled_df)
        
        return send_file(bytes_obj,
                     attachment_filename='plot.png',
                     mimetype='image/png')