From 8fe5a902699ee665f6d371efde02ae491f730dc0 Mon Sep 17 00:00:00 2001
From: Joseph Weston <joseph@weston.cloud>
Date: Fri, 9 Mar 2018 14:24:12 +0100
Subject: [PATCH] add forgotten helper module
---
zesje/helpers/image_helper.py | 41 +++++++++++++++++++++++++++++++++++
1 file changed, 41 insertions(+)
create mode 100644 zesje/helpers/image_helper.py
diff --git a/zesje/helpers/image_helper.py b/zesje/helpers/image_helper.py
new file mode 100644
index 000000000..3475b910e
--- /dev/null
+++ b/zesje/helpers/image_helper.py
@@ -0,0 +1,41 @@
+"""Utilities for dealing with images"""
+
+import numpy as np
+import cv2
+
+def get_widget_image(image_path, widget):
+ box = (widget.top, widget.bottom, widget.left, widget.right)
+ raw_image = get_box(cv2.imread(image_path), box, padding=0.3)
+ return cv2.imencode(".jpg", raw_image)[1].tostring()
+
+
+def guess_dpi(image_array):
+ h, *_ = image_array.shape
+ resolutions = np.array([1200, 600, 300, 200, 150, 120, 100, 75, 60, 50, 40])
+ return resolutions[np.argmin(abs(resolutions - 25.4 * h / 297))]
+
+
+def get_box(image_array, box, padding):
+ """Extract a subblock from an array corresponding to a scanned A4 page.
+
+ Parameters:
+ -----------
+ image_array : 2D or 3D array
+ The image source.
+ box : 4 floats (top, bottom, left, right)
+ Coordinates of the bounding box in inches. By due to differing
+ traditions, box coordinates are counted from the bottom left of the
+ image, while image array coordinates are from the top left.
+ padding : float
+ Padding around box borders in inches.
+ """
+ h, w, *_ = image_array.shape
+ dpi = guess_dpi(image_array)
+ box = np.array(box)
+ box += (padding, -padding, -padding, padding)
+ box = (np.array(box) * dpi).astype(int)
+ # Here we are not returning the lowest pixel of the image because otherwise
+ # the numpy slicing is not correct.
+ top, bottom = min(h, box[0]), max(1, box[1])
+ left, right = max(0, box[2]), min(w, box[3])
+ return image_array[-top:-bottom, left:right]
--
GitLab