Add custom thumbnailer

src/pretix/helpers/thumb.py

@@ -0,0 +1,75 @@
+import hashlib
+from io import BytesIO
+
+from django.core.files.base import ContentFile
+from django.core.files.storage import default_storage
+from PIL import Image
+
+from pretix.helpers.models import Thumbnail
+
+
+class ThumbnailError(Exception):
+    pass
+
+
+def get_sizes(size, imgsize):
+    crop = False
+    if size.endswith('^'):
+        crop = True
+        size = size[:-1]
+
+    if 'x' in size:
+        size = [int(p) for p in size.split('x')]
+    else:
+        size = [int(size), int(size)]
+
+    if crop:
+        wfactor = min(1, size[0] / imgsize[0])
+        hfactor = min(1, size[1] / imgsize[1])
+        if wfactor > hfactor:
+            return (int(size[0]), int(imgsize[1] * hfactor)), \
+                   (0, int((imgsize[1] * wfactor - size[1]) / 2), size[0], int((imgsize[1] * wfactor + size[1]) / 2))
+        else:
+            return (int(imgsize[0] * hfactor), int(size[1])), \
+                   (int((imgsize[0] * hfactor - size[0]) / 2), 0, int((imgsize[0] * hfactor + size[0]) / 2), size[1])
+    else:
+        wfactor = min(1, size[0] / imgsize[0])
+        hfactor = min(1, size[1] / imgsize[1])
+        if wfactor < hfactor:
+            return (size[0], int(imgsize[1] * wfactor)), None
+        else:
+            return (int(imgsize[0] * hfactor), size[1]), None
+
+
+def create_thumbnail(source, size):
+    if isinstance(source, str):
+        source = default_storage.open(source)
+    image = Image.open(BytesIO(source.read()))
+    try:
+        image.load()
+    except:
+        raise ThumbnailError('Could not load image')
+
+    scale, crop = get_sizes(size, image.size)
+    image = image.resize(scale)
+    print(scale, crop)
+    if crop:
+        image = image.crop(crop)
+
+    checksum = hashlib.md5(image.tobytes()).hexdigest()
+    name = checksum + '.' + size.replace('^', 'c') + '.png'
+    buffer = BytesIO()
+    image.save(fp=buffer, format='PNG')
+    imgfile = ContentFile(buffer.getvalue())
+
+    t = Thumbnail.objects.create(source=source, size=size)
+    t.thumb.save(name, imgfile)
+    return t
+
+
+def get_thumbnail(source, size):
+    # Assumes files are immutable
+    try:
+        return Thumbnail.objects.get(source=source, size=size)
+    except Thumbnail.DoesNotExist:
+        return create_thumbnail(source, size)