holmes2/ela.py at main · Omoshirokunai/holmes2 · GitHub

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"""
error level analysis

script that displays the output of ela on an image gotten from holmes.py
"""

from PIL import Image, ImageChops, ImageEnhance
import sys, os.path
import start_screen
import streamlit as st


def convert_to_ela_image(path, quality):
    filename = path
    resaved_filename = filename.split('.')[0] + '.resaved.jpg'
    ELA_filename = filename.split('.')[0] + '.ela.png'

    im = Image.open(filename).convert('RGB')
    im.save(resaved_filename, 'JPEG', quality=quality)
    resaved_im = Image.open(resaved_filename)

    ela_im = ImageChops.difference(resaved_im,im)

    extrema = ela_im.getextrema()
    max_diff = max([ex[1] for ex in extrema])
    if max_diff == 0:
        max_diff = 1
    scale = 255.0 / max_diff

    ela_im = ImageEnhance.Brightness(ela_im).enhance(scale)

    return ela_im

def app():
    st.header("Error level Analysis")
    st.info("Error level analysis is a technique that can help to identify manipulations to compressed (JPEG) images by detecting the distribution of error introduced after resaving the image at a specific compression rate")
    try:
        if start_screen.x != None:
            col1, col2 = st.beta_columns((1,2))
            with col1:
                value = st.slider("compression rate",1,255,95)

                p = convert_to_ela_image(start_screen.x,value)
                # p = convert_to_ela_image(metadata.im,value)
                extrema = p.getextrema()
                max_diff = max([ex[1] for ex in extrema])
                # st.write("Maximum difference was %d" % (max_diff))
            with col2:
                st.image(p,use_column_width=True)
        else:
            st.error("no image selected")
    except AttributeError:
        st.error("no image selected")