utils.py

# Eyegrade: grading multiple choice questions with a webcam
# Copyright (C) 2010-2011 Jesus Arias Fisteus
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see
# <http://www.gnu.org/licenses/>.
#

import array
import time

from .. import utils
from .. import imageproc

# Import the cv module. If new style bindings not found, use the old ones:
try:
    import cv
    cv_new_style = True
except ImportError:
    from .. import cvwrapper
    cv = cvwrapper.CVWrapperObject()
    cv_new_style = False

def bitmap_to_image(image_width, image_height, bitmap):
    """Converts an array of bytes into an IPL image.

       Bitmap must be an array.array of type 'B' (unsigned bytes). The
       byte 0 represents the 8 pixels to the upper-left of the image.
       In that byte, the most significative bit is the left-most bit
       of the row. The rest of the bytes go from left to right, up to
       bottom. Each row is represented by an integer number of bytes,
       with the possibility of unused bits in the last byte of each row.

       The returned IPL image will have depth 8 and 1 channel. Pixels
       will be either 255 or 0.

    """
    assert(bitmap.typecode == 'B')
    image = cv.CreateImage((image_width, image_height), 8, 1)
    byte_pos = 0
    bytes_per_row = (image_width + 7) // 8
    masks = (1 << 7, 1 << 6, 1 << 5, 1 << 4, 1 << 3, 1 << 2, 1 << 1, 1)
    for i in range(0, image_height):
        row_pos = 0
        for j in range(0, bytes_per_row):
            byte = bitmap[byte_pos]
            byte_pos += 1
            for k in range(0, 8):
                image[i, row_pos] = 255 if byte & masks[k] else 0
                row_pos += 1
                if row_pos == image_width:
                    break
    return image

def image_to_bitmap(image):
    """Converts an IPL image into an array of bytes.

       See bitmap_to_image() for details.

   """
    assert(image.depth == 8 and image.nChannels == 1)
    bytes_per_row = (image.width + 7) // 8
    bitmap_list = []
    for i in range(0, image.height):
        row_pos = 0
        for j in range(0, bytes_per_row):
            byte = 0
            for k in range(0, 8):
                byte = byte | (image[i, row_pos] > 0) << (7 - k)
                row_pos += 1
                if row_pos == image.width:
                    break
            bitmap_list.append(byte)
    return array.array('B', bitmap_list)

def process_exam(bitmap, imageproc_context, exam_config, student_ids):
    """Processes and grades an exam represented as a bitmap.

       Returns an XML-formatted string.
       See bitmap_to_image() for the format of the bitmap.

    """
    image = bitmap_to_image(640, 480, bitmap)
    cv.SaveImage('/tmp/eyegrade-server-%d.png'%time.time(), image)
    solutions = exam_config.solutions
    dimensions = exam_config.dimensions
    id_num_digits = exam_config.id_num_digits
    im_id = 0
    imageproc_options = imageproc.ExamCapture.get_default_options()
    imageproc_options['capture-from-file'] = True
    imageproc_options['capture-proc-ipl'] = image
    if student_ids is not None and student_ids != []:
        imageproc_options['read-id'] = True
        imageproc_options['id-num-digits'] = id_num_digits
    image = imageproc.ExamCapture(dimensions, imageproc_context,
                                  imageproc_options)
    image.detect_safe()
    success = image.success
    exam = None
    if image.status['infobits']:
        model = utils.decode_model(image.bits)
        if model is not None and model in solutions:
            exam = utils.Exam(image, model, solutions[model],
                              student_ids, im_id, False,
                              exam_config.score_weights, imageproc.save_image)
            exam.grade()
        else:
            success = False
    return build_answer(success, exam)

def build_answer(success, exam):
    """Given a processed eyegrade.utils.Exam, returns its XML-formatted string.
    """
    parts = []
    parts.append('<output>')
    parts.append('<ok>{0}</ok>'.format('true' if success else 'false'))
    if success:
        parts.append('<model>{0}</model>'.format(exam.model))
        student_id = exam.student_id
        if student_id is None or student_id == '-1':
            student_id = ''
        student_name = exam.get_student_name()
        if student_name is None:
            student_name = ''
        parts.append('<student id="{0}">{1}</student>'.format(student_id,
                                                              student_name))
        parts.append('<result><good>{0}</good><bad>{1}</bad>'
                     '<blank>{2}</blank><unclear>{3}</unclear>'
                     '</result>'.format(exam.score[0], exam.score[1],
                                        exam.score[2], exam.score[3]))
        parts.append('<answers>')
        for i in range(0, len(exam.correct)):
            parts.append('<answer num="{0}" correct="{1}" answered="{2}"'
                         ' solution="{3}" />'\
                             .format(i + 1,
                                     'true' if exam.correct[i] else 'false',
                                     exam.image.decisions[i],
                                     exam.solutions[i]))
        parts.append('</answers>')
        parts.append('<geometry>')
        for i in range(0, len(exam.image.centers)):
            parts.append('<question num="{0}">'.format(i + 1))
            for j in range(0, len(exam.image.centers[i])):
                center = exam.image.centers[i][j]
                diagonal = exam.image.diagonals[i][j]
                parts.append('<cell choice="{0}" center_x="{1[0]}"'
                             ' center_y="{1[1]}" diagonal="{2}" />'.\
                                 format(j + 1, center, diagonal))
            parts.append('</question>')
        parts.append('</geometry>')
    parts.append('</output>')
    return ''.join(parts)

def save_as_bitmap(image_filename, bitmap_filename):
    import eyegrade.imageproc
    image = cv.LoadImage(image_filename)
    bitmap = image_to_bitmap(eyegrade.imageproc.rgb_to_gray(image))
    with open(bitmap_filename, 'wb') as f:
        bitmap.tofile(f)

def test():
    image = cv.LoadImage('../captures/test-001-processed.png')
    image_proc = imageproc.pre_process(image)
    bitmap = image_to_bitmap(image_proc)
    image2 = bitmap_to_image(image_proc.width, image_proc.height, bitmap)
    cv.SaveImage('/tmp/test.png', image2)

def parse_cookie(cookie):
    name_val = cookie.split(';')[0].split('=')
    return name_val[0], name_val[1]

def read_session_cookie(http_response):
    headers = http_response.getheaders()
    for name, value in headers:
        if name == 'set-cookie':
            cookie_name, cookie_value = parse_cookie(value)
            print cookie_name, cookie_value
            if cookie_name == 'session_id':
                return cookie_value
    return None

def test_server(host, image_filename, preprocess=True):
    """Sends a valid request to the server in order to test it."""
    import httplib
    import sys

    headers = {}

    # First, send a config file
    with open('../doc/sample-files/exam.eye') as f:
        data = f.read()
    conn = httplib.HTTPConnection(host)
    headers['Content-type'] = 'application/x-eyegrade-exam-config'
    conn.request('POST', '/init', data, headers)
    response = conn.getresponse()
    if response.status == 200:
        print 'Exam config file succesfully sent'
        session_id = read_session_cookie(response)
        conn.close()
    else:
        print >> sys.stderr, response.status, response.reason
        print response.read()
        conn.close()
        sys.exit(1)

    if session_id is not None:
        headers['Cookie'] = 'session_id=' + session_id

    # Send a student list
    headers['Content-type'] = 'application/x-eyegrade-student-list'
    data='100099999\tJohn Doe\n100099998\tJane Doe\n'
    conn = httplib.HTTPConnection(host)
    conn.request('POST', '/students', data, headers)
    response = conn.getresponse()
    if response.status == 200:
        print 'Student list succesfully sent'
        conn.close()
    else:
        print >> sys.stderr, response.status, response.reason
        print response.read()
        conn.close()
        sys.exit(1)

    # Then, send an image
    image = cv.LoadImage(image_filename)
    if preprocess:
        bitmap = image_to_bitmap(imageproc.pre_process(image))
    else:
        bitmap = image_to_bitmap(imageproc.rgb_to_gray(image))
    headers['Content-type'] = 'application/x-eyegrade-bitmap'
    success = False
    counter = 0
    while not success and counter < 32:
        conn = httplib.HTTPConnection(host)
        conn.request('POST', '/process', bitmap, headers)
        response = conn.getresponse()
        if response.status == 200:
            result = response.read()
            print result
            if result.strip() != '<output><ok>false</ok></output>':
                success = True
        else:
            print >> sys.stderr, response.status, response.reason
            print response.read()
            break
        conn.close()
        counter += 1

    # Close session
    del headers['Content-type']
    headers['Content-length'] = '0'
    conn = httplib.HTTPConnection(host)
    conn.request('POST', '/close', '', headers=headers)
    response = conn.getresponse()
    if response.status == 200:
        print 'Session succesfully closed'
        conn.close()
    else:
        print >> sys.stderr, response.status, response.reason
        print response.read()
        conn.close()
        sys.exit(1)