在this thread出现问题之后，当我使用Django Admin时，我的models.py仍然存在很大问题。这是我的代码（我删除了与我的问题无关的内容）：
from django.core.files.uploadedfile import InMemoryUploadedFile
from PIL import Image as Img
import StringIO
class Mymodel(models.Model):
photo = models.ImageField(upload_to="photo/", blank=True, null=True)
def save(self, *args, **kwargs):
width = 500
height = 500
size = (width,height)
if self.photo:
image = Img.open(StringIO.StringIO(self.photo.read()))
(imw, imh) = image.size
if (imw>width) or (imh>height) :
image.thumbnail(size, Img.ANTIALIAS)
#If RGBA, convert transparency
if image.mode == "RGBA":
image.load()
background = Img.new("RGB", image.size, (255, 255, 255))
background.paste(image, mask=image.split()[3]) #3 is alpha channel
image=background
output = StringIO.StringIO()
image.save(output, format='JPEG', quality=60)
output.seek(0)
self.photo = InMemoryUploadedFile(output,'ImageField', "%s.jpg" %self.photo_principale.name.split('.')[0], 'image/jpeg', output.len, None)
try:
this = Mymodel.objects.get(id=self.id)
if this.photo != self.photo:
this.photo.delete(save=False)
except: pass # when new photo then we do nothing, normal case
super(Mymodel, self).save(*args, **kwargs)
可行，文件上传，调整大小并在需要时成功转换为JPEG。问题是，每当我编辑它时，即使不上传新图像，它也会创建一个新图像（例如，我第一次使用图像保存我的模型＆＃34; hello.jpg＆＃34;然后我编辑它，它会创建一个名为＆＃34; hello_1.jpg＆＃34;的新图像，即使我没有上传任何内容）。 我认为try / except块只在编辑时才有效（所以没有新的文件上传），但显然不是。
提前感谢您的帮助：）
答案 0 :(得分：5)
最终解决方案，为我工作：
from django.core.files.uploadedfile import InMemoryUploadedFile
from PIL import Image as Img
import StringIO
from django.db.models.signals import post_delete
from django.dispatch import receiver
Class Mymodel(models.Model):
photo= models.ImageField(upload_to="photo/", blank=True, null=True)
def save(self, *args, **kwargs):
width = 500
height = 500
size = (width,height)
isSame = False
if self.photo:
try:
this = Mymodel.objects.get(id=self.id)
if this.photo==self.photo :
isSame= True
except: pass # when new photo then we do nothing, normal case
image = Img.open(StringIO.StringIO(self.photo.read()))
(imw, imh) = image.size
if (imw>width) or (imh>height) :
image.thumbnail(size, Img.ANTIALIAS)
#If RGBA, convert transparency
if image.mode == "RGBA":
image.load()
background = Img.new("RGB", image.size, (255, 255, 255))
background.paste(image, mask=image.split()[3]) # 3 is the alpha channel
image=background
output = StringIO.StringIO()
image.save(output, format='JPEG', quality=60)
output.seek(0)
self.photo = InMemoryUploadedFile(output,'ImageField', "%s.jpg" %self.photo.name.split('.')[0], 'image/jpeg', output.len, None)
try:
this = Mymodel.objects.get(id=self.id)
if this.photo==self.photo or isSame :
self.photo=this.photo
else :
this.photo.delete(save=False)
except: pass # when new photo then we do nothing, normal case
super(Mymodel, self).save(*args, **kwargs)
@receiver(post_delete, sender=Mymodel)
def photo_post_delete_handler(sender, **kwargs):
instance = kwargs['instance']
storage, path = instance.photo.storage, instance.photo.path
if (path!='.') and (path!='/') and (path!='photo/') and (path!='photo/.'):
storage.delete(path)
希望它可以帮助某人;）
答案 1 :(得分：0)
尝试：
if self.photo.name != '':
或
if self.photo.size > 0:
答案 2 :(得分：0)
这是基于Ralph的答案为python 3和django 2工作的。
首先，您必须导入io：
from io import BytesIO
要调整大小并在必要时添加白色背景：
def resize_with_white_background(pil_image: Image.Image, desired_width, desired_height):
img_copy = pil_image.copy()
# get proportioned image ie (if image is 200X600 and trying to resize to 100X200
# thumbnail will NOT do this but resize to keep the ratio so it would be 67x200 to maintain the ratio (uses the larger)
# img_copy changed in place (does not create new image)
img_copy.thumbnail((desired_width, desired_height), Image.ANTIALIAS)
# create white background
background = Image.new('RGB', (desired_width, desired_height), (255,255,255))
pixels_to_move_left = int((background.width - img_copy.width) * 0.50) # centered horizontally
pixels_to_move_down = int((background.height - img_copy.height) * 0.50) # centered vertically
# paste image into white background box argument tells where to paste
background.paste(img_copy, box=(pixels_to_move_left, pixels_to_move_down))
return background # this will return the background with img_copy pasted in and will be resized to fit your desired size
要将尺寸调整后的图像设置为，然后ImageField在模型中创建一个方法：
def set_image(self, desired_width, desired_height):
try:
this = MyModel.objects.get(id=self.id)
except MyModel.DoesNotExist:
pass
else:
# will not resize or set to new image (this avoids setting image every single time you edit and save
if this.image == self.image and (self.image.width, self.image.height) == (desired_width, desired_height):
return
im = Image.open(BytesIO(self.image.read()))
resized_image = resize_with_white_background(
pil_image=im,
desired_width=desired_width,
desired_height=desired_height
)
# output (file like object)
output = BytesIO()
# save image into file-like object
resized_image.save(output, format='JPEG', quality=94)
# get size of file
a_size = output.tell()
# reset to beginning of file-like object
output.seek(0)
self.image.file = InMemoryUploadedFile(
output,
'ImageField',
f"{self.image.name.split('.')[0]}.jpg",
'image/jpeg',
a_size,
None
)
在调用Super（）。save（* args，** kwargs）方法之前，重写模型的save（）方法并调用set_image（）方法
def save(self, *args, **kwargs):
self.set_image(
desired_width=100, # can be whatever you want
desired_height=200
)
super().save(*args, **kwargs)