How to obtain image size using standard Python class (without using external library)?

Question

I am using Python 2.5. And using the standard classes from Python, I want to determine the image size of a file.

I\'ve heard PIL (Python Image Library), but it requi

Answer 1

That code does accomplish 2 things:

• Getting the image dimension

• Find the real EOF of a jpg file

Well when googling I was more interest in the later one. The task was to cut out a jpg file from a datastream. Since I I didn't find any way to use Pythons 'image' to a way to get the EOF of so jpg-File I made up this.

Interesting things /changes/notes in this sample:

• extending the normal Python file class with the method uInt16 making source code better readable and maintainable. Messing around with struct.unpack() quickly makes code to look ugly

• Replaced read over'uninteresting' areas/chunk with seek

• Incase you just like to get the dimensions you may remove the line:

  hasChunk = ord(byte) not in range( 0xD0, 0xDA) + [0x00] 
  

  ->since that only get's important when reading over the image data chunk and comment in

  #break
  

  to stop reading as soon as the dimension were found. ...but smile what I'm telling - you're the Coder ;)

    import struct
    import io,os
  
    class myFile(file):
  
        def byte( self ):
             return file.read( self,  1);
  
        def uInt16( self ):
             tmp = file.read( self,  2)
             return struct.unpack( ">H", tmp )[0];
  
    jpeg = myFile('grafx_ui.s00_\\08521678_Unknown.jpg', 'rb')
  
    try:
        height = -1
        width  = -1
        EOI    = -1
  
        type_check = jpeg.read(2)
        if type_check != b'\xff\xd8':
          print("Not a JPG")
  
        else:
  
          byte = jpeg.byte()
  
          while byte != b"":
  
            while byte != b'\xff': byte = jpeg.byte()
            while byte == b'\xff': byte = jpeg.byte()
  
  
            # FF D8       SOI Start of Image
            # FF D0..7  RST DRI Define Restart Interval inside CompressedData
            # FF 00           Masked FF inside CompressedData
            # FF D9       EOI End of Image
            # http://en.wikipedia.org/wiki/JPEG#Syntax_and_structure
            hasChunk = ord(byte) not in range( 0xD0, 0xDA) + [0x00]
            if hasChunk:
                 ChunkSize   =  jpeg.uInt16()  - 2
                 ChunkOffset =  jpeg.tell()
                 Next_ChunkOffset = ChunkOffset + ChunkSize
  
  
            # Find bytes \xFF \xC0..C3 That marks the Start of Frame
            if (byte >= b'\xC0' and byte <= b'\xC3'):
  
              # Found  SOF1..3 data chunk - Read it and quit
              jpeg.seek(1, os.SEEK_CUR)
              h = jpeg.uInt16()
              w = jpeg.uInt16()
  
  
              #break
  
  
            elif (byte == b'\xD9'):
                 # Found End of Image
                 EOI = jpeg.tell()
                 break
            else:
                # Seek to next data chunk
               print "Pos: %.4x %x" % (jpeg.tell(), ChunkSize)
  
            if hasChunk:       
               jpeg.seek(Next_ChunkOffset)
  
            byte = jpeg.byte()
  
          width  = int(w)
          height = int(h)
  
          print("Width: %s, Height: %s  JpgFileDataSize: %x" % (width, height, EOI))
    finally:
        jpeg.close()
  

Answer 2

Stumbled upon this one but you can get it by using the following as long as you import numpy.

import numpy as np

[y, x] = np.shape(img[:,:,0])

It works because you ignore all but one color and then the image is just 2D so shape tells you how bid it is. Still kinda new to Python but seems like a simple way to do it.

Answer 3

Kurts answer needed to be slightly modified to work for me.

First, on ubuntu: sudo apt-get install python-imaging

Then:

from PIL import Image
im=Image.open(filepath)
im.size # (width,height) tuple

Check out the handbook for more info.

Answer 4

If you happen to have ImageMagick installed, then you can use 'identify'. For example, you can call it like this:

path = "//folder/image.jpg"
dim = subprocess.Popen(["identify","-format","\"%w,%h\"",path], stdout=subprocess.PIPE).communicate()[0]
(width, height) = [ int(x) for x in re.sub('[\t\r\n"]', '', dim).split(',') ]