Add custom thumbnailer

src/pretix/helpers/__init__.py

@@ -0,0 +1,9 @@
+from django.apps import AppConfig
+
+
+class PretixHelpersConfig(AppConfig):
+    name = 'pretix.helpers'
+    label = 'pretixhelpers'
+
+
+default_app_config = 'pretix.helpers.PretixHelpersConfig'

src/pretix/helpers/migrations/0001_initial.py

@@ -0,0 +1,29 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.11 on 2018-03-20 07:36
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    initial = True
+
+    dependencies = [
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='Thumbnail',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('source', models.CharField(max_length=255)),
+                ('size', models.CharField(max_length=255)),
+                ('thumb', models.FileField(upload_to='')),
+            ],
+        ),
+        migrations.AlterUniqueTogether(
+            name='thumbnail',
+            unique_together=set([('source', 'size')]),
+        ),
+    ]

src/pretix/helpers/models.py

@@ -0,0 +1,10 @@
+from django.db import models
+
+
+class Thumbnail(models.Model):
+    source = models.CharField(max_length=255)
+    size = models.CharField(max_length=255)
+    thumb = models.FileField(upload_to='pub/thumbs/')
+
+    class Meta:
+        unique_together = (('source', 'size'),)

src/pretix/helpers/templatetags/thumb.py

@@ -0,0 +1,18 @@
+import logging
+
+from django import template
+from django.core.files.storage import default_storage
+
+from pretix.helpers.thumb import get_thumbnail
+
+register = template.Library()
+logger = logging.getLogger(__name__)
+
+
+@register.filter
+def thumb(source, arg):
+    try:
+        return get_thumbnail(source, arg).thumb.url
+    except:
+        logger.exception('Failed to create thumbnail')
+        return default_storage.url(source)

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)