[ocrfeeder] Add the ImageDeskewer class

[Joaquim Manuel Pereira Rocha <jrocha src gnome org>]

commit 6b1b4550cf7b64619453085d9bd816c3b47040d1
Author: Joaquim Rocha <jrocha igalia com>
Date:   Fri Jul 16 11:39:11 2010 +0200

    Add the ImageDeskewer class

 feeder/layoutAnalysis.py |   70 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 70 insertions(+), 0 deletions(-)
---
diff --git a/feeder/layoutAnalysis.py b/feeder/layoutAnalysis.py
index 9a49e26..3b12171 100644
--- a/feeder/layoutAnalysis.py
+++ b/feeder/layoutAnalysis.py
@@ -23,7 +23,9 @@ from util import graphics
 from util.constants import OCRFEEDER_DEBUG, DTP
 from studio.dataHolder import DataBox
 from imageManipulation import ImageProcessor
+import Image
 import re
+import math
 
 NONE = 0
 TOP = -1
@@ -375,6 +377,74 @@ class BlockRetriever:
                 debug(block)
         return blocks
 
+class ImageDeskewer(object):
+
+    def __init__(self, bg_color = 255,
+                 contrast_tolerance = 120):
+        self.angle_step = 2
+        self.bg_color = bg_color
+        self.contrast_tolerance = contrast_tolerance
+
+    def deskew(self, image_path, deskewed_image_path):
+        try:
+            image = Image.open(image_path)
+        except:
+            return False
+        deskew_angle = self.get_deskew_angle(image)
+        if not deskew_angle:
+            return False
+        deskewed_image = image.convert('RGBA').rotate(-deskew_angle,
+                                                       Image.BICUBIC)
+        collage = Image.new('L', image.size, color = self.bg_color)
+        collage.paste(deskewed_image, None, deskewed_image)
+        collage = collage.convert('RGB')
+        collage.save(deskewed_image_path, format=image.format)
+        return True
+
+    def get_deskew_angle(self, image_orig):
+        width, height = image_orig.size
+        resize_ratio = 600 / float(width)
+        # Convert image to grayscale and resize it for better
+        # performance
+        image = image_orig.convert('L')
+        image = image.resize((int(round(width * resize_ratio)),
+                              int(round(height * resize_ratio))))
+        width, height = image.size
+        max_r = int(round(math.sqrt(width ** 2 + height ** 2)))
+        hough_accumulator = {}
+
+        for x in range(0, width):
+            for y in range(0, height - 1):
+                if y + 1 > height:
+                    break
+                color = image.getpixel((x, y))
+                color_below = image.getpixel((x, y + 1))
+                if graphics.colorsContrast(color, self.bg_color,
+                                           self.contrast_tolerance) and \
+                   graphics.colorsContrast(color, color_below,
+                                           self.contrast_tolerance):
+                   for r, angle in self.__getDistanceAndAngle(x, y):
+                       if 0 < r < max_r:
+                           vote_value = hough_accumulator.get((r, angle), 0)
+                           hough_accumulator[(r, angle)] = vote_value + 1
+
+        if not hough_accumulator:
+            return 0
+        max_voted = hough_accumulator.keys()[0]
+        for r_angle in hough_accumulator:
+            max_voted_value = hough_accumulator.get(max_voted)
+            if hough_accumulator[r_angle] > max_voted_value:
+                max_voted = r_angle
+
+        return 90 - max_voted[1]
+
+    def __getDistanceAndAngle(self, x, y):
+        for angle in range(1, 180, 1):
+            angle_radians = angle * math.pi / 180
+            r = math.cos(angle_radians) * x + math.sin(angle_radians) * y
+            r = int(round(r))
+            yield r, angle
+
 class LayoutAnalysis(object):
 
     def __init__(self,