if filename:
self.saveimage.save(filename)

def onDirectoryOpen(event):
"""
open a new image directory in new pop up
available in both thumb and img windows
"""
dirname = openDialog.show()
if dirname:
viewThumbs(dirname, kind=Toplevel)

def viewThumbs(imgdir, kind=Toplevel, numcols=None, height=400, width=500):
"""
make main or pop-up thumbnail buttons window;
uses fixed-size buttons, scrollable canvas;
sets scrollable (full) size, and places
thumbs at abs x,y coordinates in canvas;
no longer assumes all thumbs are same size:
gets max of all (x,y), some may be smaller;
"""
win = kind()
helptxt = '(press D to open other)'
win.title(appname + imgdir + ' ' + helptxt)
quit = Button(win, text='Quit', command=win.quit, bg='beige')
quit.pack(side=BOTTOM, fill=X)
canvas = ScrolledCanvas(win)
canvas.config(height=height, width=width) # init viewable window size

changes if user resizes

thumbs = makeThumbs(imgdir) # [(imgfile, imgobj)]
numthumbs = len(thumbs)
if not numcols:
numcols = int(math.ceil(math.sqrt(numthumbs))) # fixed or N x N
numrows = int(math.ceil(numthumbs / numcols)) # 3.x true div

max w|h: thumb=(name, obj), thumb.size=(width, height)

linksize = max(max(thumb[1].size) for thumb in thumbs)
trace(linksize)
fullsize = (0, 0, # upper left X,Y
(linksize numcols), (linksize numrows) ) # lower right X,Y
canvas.config(scrollregion=fullsize) # scrollable area size

rowpos = 0
savephotos = []
while thumbs:
thumbsrow, thumbs = thumbs[:numcols], thumbs[numcols:]
colpos = 0
for (imgfile, imgobj) in thumbsrow:
photo = PhotoImage(imgobj)
link = Button(canvas, image=photo)
def handler(savefile=imgfile):
ViewOne(imgdir, savefile)
link.config(command=handler, width=linksize, height=linksize)

726 | Chapter 11: Complete GUI Programs