可能重复:
保存时调整图像大小
我正在尝试在 django 中创建缩略图,正在尝试构建一个专门用于生成缩略图的自定义类。如下
from cStringIO import StringIO
from PIL import Image
class Thumbnail(object):
SIZE = (50, 50)
def __init__(self, source):
self.source = source
self.output = None
def generate(self, size=None, fit=True):
if not size:
size = self.SIZE
if not isinstance(size, tuple):
raise TypeError('Thumbnail class: The size parameter must be an instance of a tuple.')
# resize properties
box = size
factor = 1
image = Image.open(self.source)
# Convert to RGB if necessary
if image.mode not in ('L', 'RGB'):
image = image.convert('RGB')
while image.size[0]/factor > 2*box[0] and image.size[1]*2/factor > 2*box[1]:
factor *=2
if factor > 1:
image.thumbnail((image.size[0]/factor, image.size[1]/factor), Image.NEAREST)
#calculate the cropping box and get the cropped part
if fit:
x1 = y1 = 0
x2, y2 = image.size
wRatio = 1.0 * x2/box[0]
hRatio = 1.0 * y2/box[1]
if hRatio > wRatio:
y1 = int(y2/2-box[1]*wRatio/2)
y2 = int(y2/2+box[1]*wRatio/2)
else:
x1 = int(x2/2-box[0]*hRatio/2)
x2 = int(x2/2+box[0]*hRatio/2)
image = image.crop((x1,y1,x2,y2))
#Resize the image with best quality algorithm ANTI-ALIAS
image.thumbnail(box, Image.ANTIALIAS)
# save image to memory
temp_handle = StringIO()
image.save(temp_handle, 'png')
temp_handle.seek(0)
self.output = temp_handle
return self
def get_output(self):
self.output.seek(0)
return self.output.read()
该课程的目的是让我可以在不同的位置使用它来动态生成缩略图。该类完美运行,我直接在视图下对其进行了测试。我在表单的保存方法中实现了缩略图类,以在保存时调整原始图像的大小。
在我的设计中,我有两个缩略图字段。我能够生成一个缩略图,如果我尝试生成两个它会崩溃并且我已经卡了几个小时不知道是什么问题。
这是我的模型
class Image(models.Model):
article = models.ForeignKey(Article)
title = models.CharField(max_length=100, null=True, blank=True)
src = models.ImageField(upload_to='publication/image/')
r128 = models.ImageField(upload_to='publication/image/128/', blank=True, null=True)
r200 = models.ImageField(upload_to='publication/image/200/', blank=True, null=True)
uploaded_at = models.DateTimeField(auto_now=True)
这是我的表格
class ImageForm(models.ModelForm):
"""
"""
class Meta:
model = Image
fields = ('src',)
def save(self, commit=True):
instance = super(ImageForm, self).save(commit=True)
instance.r128 = SimpleUploadedFile(
instance.src.name,
Thumbnail(instance.src).generate((128, 128)).get_output(),
content_type='image/png'
)
instance.r200 = SimpleUploadedFile(
instance.src.name,
Thumbnail(instance.src).generate((200, 200)).get_output(),
content_type='image/png'
)
if commit:
instance.save()
return instance
奇怪的是,当我在保存表单中删除包含 instance.r200 的行时。它工作正常,它会生成缩略图并成功存储它。一旦我添加了第二个缩略图,它就会失败..
有什么想法在这里做错了吗?
谢谢
更新:
根据评论请求,我附加了错误跟踪
IOError at /en/publication/new/
cannot identify image file
Request Method: POST
Request URL: http://127.0.0.1:8000/en/publication/new/?image-extra=
Django Version: 1.4.2
Exception Type: IOError
Exception Value:
cannot identify image file
Exception Location: /Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/PIL/Image.py in open, line 1980
Python Executable: /Users/mo/Projects/pythonic/snowflake-env/bin/python
Python Version: 2.7.2
更新
试图创建打印语句,下面是输出
Source: publication/image/tumblr_m9o7244nZM1rykg1io1_1280_11.jpg
Source: publication/image/tumblr_m9o7244nZM1rykg1io1_1280_11.jpg
ERROR:root:cannot identify image file
ERROR:django.request:Internal Server Error: /en/publication/new/
Traceback (most recent call last):
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/core/handlers/base.py", line 111, in get_response
response = callback(request, *callback_args, **callback_kwargs)
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/contrib/auth/decorators.py", line 20, in _wrapped_view
return view_func(request, *args, **kwargs)
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/db/transaction.py", line 209, in inner
return func(*args, **kwargs)
File "/Users/mo/Projects/pythonic/snowflake-env/snowflake/snowflake/apps/publication/views.py", line 69, in new
formset.save()
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/forms/models.py", line 497, in save
return self.save_existing_objects(commit) + self.save_new_objects(commit)
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/forms/models.py", line 628, in save_new_objects
self.new_objects.append(self.save_new(form, commit=commit))
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/forms/models.py", line 727, in save_new
obj = form.save(commit=False)
File "/Users/mo/Projects/pythonic/snowflake-env/snowflake/snowflake/apps/publication/forms.py", line 113, in save
Thumbnail(instance.src).generate((200, 200)).get_output(),
File "/Users/mo/Projects/pythonic/snowflake-env/snowflake/snowflake/apps/core/utils.py", line 23, in generate
image = Image.open(self.source)
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/PIL/Image.py", line 1980, in open
raise IOError("cannot identify image file")
IOError: cannot identify image file
如图所示,第一张图像打印并成功处理,第二张图像失败。
更新
在缩略图类中应用 copy() 后追溯错误更新
ERROR:root:cannot identify image file
ERROR:django.request:Internal Server Error: /en/publication/new/
Traceback (most recent call last):
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/core/handlers/base.py", line 111, in get_response
response = callback(request, *callback_args, **callback_kwargs)
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/contrib/auth/decorators.py", line 20, in _wrapped_view
return view_func(request, *args, **kwargs)
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/db/transaction.py", line 209, in inner
return func(*args, **kwargs)
File "/Users/mo/Projects/pythonic/snowflake-env/snowflake/snowflake/apps/publication/views.py", line 69, in new
formset.save()
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/forms/models.py", line 497, in save
return self.save_existing_objects(commit) + self.save_new_objects(commit)
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/forms/models.py", line 628, in save_new_objects
self.new_objects.append(self.save_new(form, commit=commit))
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/django/forms/models.py", line 727, in save_new
obj = form.save(commit=False)
File "/Users/mo/Projects/pythonic/snowflake-env/snowflake/snowflake/apps/publication/forms.py", line 113, in save
f128.write(Thumbnail(instance.src).generate((128, 128)).get_output())
File "/Users/mo/Projects/pythonic/snowflake-env/snowflake/snowflake/apps/core/utils.py", line 15, in __init__
self._pilImage = Image.open(self.source)
File "/Users/mo/Projects/pythonic/snowflake-env/lib/python2.7/site-packages/PIL/Image.py", line 1980, in open
raise IOError("cannot identify image file")
IOError: cannot identify image file
更新
最后,我设法让它工作,但我不得不将文件流式传输到 self.source 作为 belo
def __init__(self, source):
self.source = StringIO(file(source.path, "rb").read())
self.output = None
self._pilImage = Image.open(self.source)
以上是理想的方法吗?每次点击时读取文件是个好主意吗?如果没有,我的替代方案是什么?