Develop Reference

How to cv2.imread an image within a zipfile?

I'm trying to use OpenCV2 to read images withing a zipfile with cv2.imread and then resize them and save them but I can't figure out how to read those images within the zipfile. This is my code so far:
import cv2
from zipfile import ZipFile
with ZipFile("sample_images.zip", "r") as zipFile:
imgs = zipFile.namelist()
img = zipFile.open(imgs[0])
processedImg = cv2.imread(img)
This is the error I get:
Traceback (most recent call last):
File "C:/Users/Yash/Desktop/Programming/opencv test/test.py", line 8, in <module>
processedImg = cv2.imread(img)
SystemError: <built-in function imread> returned NULL without setting an error

Try this
from io import BytesIO
from zipfile import ZipFile
from PIL import Image
with ZipFile("sample_images.zip", "r") as zipFile:
imgs = zipFile.namelist()
print(imgs[0])
img = zipFile.read(imgs[0])
processedImg = Image.open(BytesIO(img))
processedImg.show()

PIL open image from base64 failed

I'm trying to convert a base64 string to image and get the following error.
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/dist-packages/PIL/Image.py", line 2288, in open
% (filename if filename else fp))
IOError: cannot identify image file <cStringIO.StringI object at 0x7fe6d9e88828>
There is no prefix like data:image/png;base64. I get the base64 string from an image and try to convert it back to an image. Here is my code.
# -*- coding: utf-8 -*-
import requests
import base64
from PIL import Image
from cStringIO import StringIO
import zipfile
r = requests.get('https://www.google.com/images/branding/googlelogo/1x/googlelogo_color_272x92dp.png', stream=False)
img = Image.open(StringIO(r.content))
b64str = base64.b64encode(img.tobytes())
data = base64.b64decode(b64str)
newimg = Image.open(StringIO(data))
And I get the error above. Can anyone help? Thanks!

You open .PNG file from the web and get the RAW image, which is RGB values, then encode that into base64 and back, which still gives you RAW RGB values which cannot be read by Image.open() because these are not an image file (jpg, png, etc), but RAW RGB values.
The most reasonable would be:
newImg = data # that's it
Or if you want to make an Image:
newImg = Image.frombytes(img.mode, img.size, data)
and get mode and size from the original image.

Storing image from StringIO to a file creates a distorted image

I stored an image to StringIO from PIL. When I store it to a file from stringIO, it doesn't produce the original image.
Code:
from PIL import Image
from cStringIO import StringIO
buff=StringIO()
img = Image.open("test.jpg")
img.save(buff,format='JPEG')
#img=img.crop((1,1,100,100))
buff.seek(0)
#Produces a distorted image
with open("vv.jpg", "w") as handle:
handle.write(buff.read())
Original Image is below
Output image is below
What is wrong with the above code

You need to use BytesIO and not StringIO.
Also the destination file has to be opened in binary mode using "wb"
Here is code that works (cStringIO is replaced with io)
from PIL import Image
from io import BytesIO
buff=BytesIO()
img = Image.open('test.jpg')
img.save(buff,format='JPEG')
#img=img.crop((1,1,100,100))
buff.seek(0)
#Produces a distorted image
with open('vv.jpg', "wb") as handle:
handle.write(buff.read())

"ValueError: cannot filter palette images" during Pytesseract Conversion

Having trouble with this error code regarding the following code for Pytesseract. (Python 3.6.1, Mac OSX)
import pytesseract
import requests
from PIL import Image
from PIL import ImageFilter
from io import StringIO, BytesIO
def process_image(url):
image = _get_image(url)
image.filter(ImageFilter.SHARPEN)
return pytesseract.image_to_string(image)
def _get_image(url):
r = requests.get(url)
s = BytesIO(r.content)
img = Image.open(s)
return img
process_image("https://www.prepressure.com/images/fonts_sample_ocra_medium.png")
Error:
/usr/local/Cellar/python3/3.6.0_1/Frameworks/Python.framework/Versions/3.6/bin/python3.6 /Users/g/pyfo/reddit/ocr.py
Traceback (most recent call last):
File "/Users/g/pyfo/reddit/ocr.py", line 20, in <module>
process_image("https://www.prepressure.com/images/fonts_sample_ocra_medium.png")
File "/Users/g/pyfo/reddit/ocr.py", line 10, in process_image
image.filter(ImageFilter.SHARPEN)
File "/usr/local/lib/python3.6/site-packages/PIL/Image.py", line 1094, in filter
return self._new(filter.filter(self.im))
File "/usr/local/lib/python3.6/site-packages/PIL/ImageFilter.py", line 53, in filter
raise ValueError("cannot filter palette images")
ValueError: cannot filter palette images
Process finished with exit code 1
Seems simple enough, but is not working. Any help would be greatly appreciated.

The image you have is a pallet-based image. You need to convert it to a full RGB image in order to use the PIL filters.
import pytesseract
import requests
from PIL import Image, ImageFilter
from io import StringIO, BytesIO
def process_image(url):
image = _get_image(url)
image = image.convert('RGB')
image = image.filter(ImageFilter.SHARPEN)
return pytesseract.image_to_string(image)
def _get_image(url):
r = requests.get(url)
s = BytesIO(r.content)
img = Image.open(s)
return img
process_image("https://www.prepressure.com/images/fonts_sample_ocra_medium.png")
You should also note that the the .convert() and .filter() methods return a copy of the image, they don't change the existing image object. You need to assign the return value to a variable as shown in the code above.
NOTE: I don't have pytesseract, so I can't check the last line of process_image().

How to open a simple image using streams in Pillow-Python

from PIL import Image
image = Image.open("image.jpg")
file_path = io.BytesIO();
image.save(file_path,'JPEG');
image2 = Image.open(file_path.getvalue());
I get this error TypeError: embedded NUL character on the last statement Image.open on running the program
What is the correct way to open a file from streams?

http://effbot.org/imagingbook/introduction.htm#more-on-reading-images
from PIL import Image
import StringIO
buffer = StringIO.StringIO()
buffer.write(open('image.jpeg', 'rb').read())
buffer.seek(0)
image = Image.open(buffer)
print image
# <PIL.JpegImagePlugin.JpegImageFile image mode=RGB size=800x600 at 0x7FE2EEE2B098>
# if we try open again
image = Image.open(buffer)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/dist-packages/PIL/Image.py", line 2028, in open
raise IOError("cannot identify image file")
IOError: cannot identify image file
Make sure you call buff.seek(0) before reading any StringIO objects. Otherwise you'll be reading from the end of the buffer, which will look like an empty file and is likely causing the error you're seeing.

Using BytesIO is much more simple, it took me a while to figure out. This allows you to read and write to zip files for example.
from PIL import Image
from io import BytesIO
# bytes of a simple 2x2 gif file
gif_bytes = b'\x47\x49\x46\x38\x39\x61\x02\x00\x02\x00\x80\x00\x00\x00\xFF\xFF\xFF\x21\xF9\x04\x00\x00\x00\x00\x00\x2C\x00\x00\x00\x00\x02\x00\x02\x00\x00\x02\x03\x44\x02\x05\x00\x3B'
gif_bytes_io = BytesIO() # or io.BytesIO()
# store the gif bytes to the IO and open as image
gif_bytes_io.write(gif_bytes)
image = Image.open(gif_bytes_io)
# optional proof of concept:
# image.show()
# save as png through a stream
png_bytes_io = BytesIO() # or io.BytesIO()
image.save(png_bytes_io, format='PNG')
print(png_bytes_io.getvalue()) # outputs the byte stream of the png