Find all images in the current directory and generate resized versions, together with a single preview file displaying all patched versions pasted together.

Resize.py

import PIL, os, math
from PIL import Image

resizeWidth=500

allfiles=os.listdir(os.getcwd())
filelist=[f for f in allfiles if f[-4:] in ['.jpg','.JPG','.jpeg','.JPEG','.png','.PNG']]
Nimages=len(filelist)
im0=Image.open(filelist[0])
w,h=im0.size
neww=resizeWidth
newh=int(round((float(neww)/float(w))*h))
bigim=Image.new("RGB",(2*neww,int(math.ceil(float(Nimages)/2.0))*newh))

row,col=0,0
for imname in filelist:
    im=Image.open(imname)
    small=im.resize((neww,newh),Image.ANTIALIAS)
    small.save("small_"+imname[0:-4]+".png")
    bigim.paste(small,(col*neww,row*newh,(col+1)*neww,(row+1)*newh))
    print row,col
    col=col+1
    if col>1:
        col=0
        row=row+1
bigim.save("Preview.png")