check_dpi: use OcrdExif instead identify callout

sbb_newspapers_org_image/utils/pil_cv2.py

@@ -0,0 +1,24 @@
+from PIL import Image
+import numpy as np
+from ocrd_models import OcrdExif
+from cv2 import COLOR_GRAY2BGR, COLOR_RGB2BGR, cvtColor, imread
+
+# from sbb_binarization
+
+def cv2pil(img):
+    return Image.fromarray(img.astype('uint8'))
+
+def pil2cv(img):
+    # from ocrd/workspace.py
+    color_conversion = COLOR_GRAY2BGR if img.mode in ('1', 'L') else  COLOR_RGB2BGR
+    pil_as_np_array = np.array(img).astype('uint8') if img.mode == '1' else np.array(img)
+    return cvtColor(pil_as_np_array, color_conversion)
+
+def check_dpi(image_filename):
+    exif = OcrdExif(Image.open(image_filename))
+    print(exif.to_xml())
+    resolution = exif.resolution
+    if exif.resolutionUnit == 'cm':
+        resolution /= 2.54
+    return int(resolution)
+