Tkinter canvas zoom + move/pan
Advanced zoom example. Like in Google Maps.
Example video (longer video here):
It zooms only a tile, but not the whole image. So the zoomed tile occupies constant memory and not crams it with a huge resized image for the large zooms. For the simplified zoom example look here.
Tested on Windows 7 64-bit and Python 3.6.2.
Do not forget to place a path to your image at the end of the script.
# -*- coding: utf-8 -*-
# Advanced zoom example. Like in Google Maps.
# It zooms only a tile, but not the whole image. So the zoomed tile occupies
# constant memory and not crams it with a huge resized image for the large zooms.
import random
import tkinter as tk
from tkinter import ttk
from PIL import Image, ImageTk
class AutoScrollbar(ttk.Scrollbar):
''' A scrollbar that hides itself if it's not needed.
Works only if you use the grid geometry manager '''
def set(self, lo, hi):
if float(lo) <= 0.0 and float(hi) >= 1.0:
self.grid_remove()
else:
self.grid()
ttk.Scrollbar.set(self, lo, hi)
def pack(self, **kw):
raise tk.TclError('Cannot use pack with this widget')
def place(self, **kw):
raise tk.TclError('Cannot use place with this widget')
class Zoom_Advanced(ttk.Frame):
''' Advanced zoom of the image '''
def __init__(self, mainframe, path):
''' Initialize the main Frame '''
ttk.Frame.__init__(self, master=mainframe)
self.master.title('Zoom with mouse wheel')
# Vertical and horizontal scrollbars for canvas
vbar = AutoScrollbar(self.master, orient='vertical')
hbar = AutoScrollbar(self.master, orient='horizontal')
vbar.grid(row=0, column=1, sticky='ns')
hbar.grid(row=1, column=0, sticky='we')
# Create canvas and put image on it
self.canvas = tk.Canvas(self.master, highlightthickness=0,
xscrollcommand=hbar.set, yscrollcommand=vbar.set)
self.canvas.grid(row=0, column=0, sticky='nswe')
self.canvas.update() # wait till canvas is created
vbar.configure(command=self.scroll_y) # bind scrollbars to the canvas
hbar.configure(command=self.scroll_x)
# Make the canvas expandable
self.master.rowconfigure(0, weight=1)
self.master.columnconfigure(0, weight=1)
# Bind events to the Canvas
self.canvas.bind('<Configure>', self.show_image) # canvas is resized
self.canvas.bind('<ButtonPress-1>', self.move_from)
self.canvas.bind('<B1-Motion>', self.move_to)
self.canvas.bind('<MouseWheel>', self.wheel) # with Windows and MacOS, but not Linux
self.canvas.bind('<Button-5>', self.wheel) # only with Linux, wheel scroll down
self.canvas.bind('<Button-4>', self.wheel) # only with Linux, wheel scroll up
self.image = Image.open(path) # open image
self.width, self.height = self.image.size
self.imscale = 1.0 # scale for the canvaas image
self.delta = 1.3 # zoom magnitude
# Put image into container rectangle and use it to set proper coordinates to the image
self.container = self.canvas.create_rectangle(0, 0, self.width, self.height, width=0)
# Plot some optional random rectangles for the test purposes
minsize, maxsize, number = 5, 20, 10
for n in range(number):
x0 = random.randint(0, self.width - maxsize)
y0 = random.randint(0, self.height - maxsize)
x1 = x0 + random.randint(minsize, maxsize)
y1 = y0 + random.randint(minsize, maxsize)
color = ('red', 'orange', 'yellow', 'green', 'blue')[random.randint(0, 4)]
self.canvas.create_rectangle(x0, y0, x1, y1, fill=color, activefill='black')
self.show_image()
def scroll_y(self, *args, **kwargs):
''' Scroll canvas vertically and redraw the image '''
self.canvas.yview(*args, **kwargs) # scroll vertically
self.show_image() # redraw the image
def scroll_x(self, *args, **kwargs):
''' Scroll canvas horizontally and redraw the image '''
self.canvas.xview(*args, **kwargs) # scroll horizontally
self.show_image() # redraw the image
def move_from(self, event):
''' Remember previous coordinates for scrolling with the mouse '''
self.canvas.scan_mark(event.x, event.y)
def move_to(self, event):
''' Drag (move) canvas to the new position '''
self.canvas.scan_dragto(event.x, event.y, gain=1)
self.show_image() # redraw the image
def wheel(self, event):
''' Zoom with mouse wheel '''
x = self.canvas.canvasx(event.x)
y = self.canvas.canvasy(event.y)
bbox = self.canvas.bbox(self.container) # get image area
if bbox[0] < x < bbox[2] and bbox[1] < y < bbox[3]: pass # Ok! Inside the image
else: return # zoom only inside image area
scale = 1.0
# Respond to Linux (event.num) or Windows (event.delta) wheel event
if event.num == 5 or event.delta == -120: # scroll down
i = min(self.width, self.height)
if int(i * self.imscale) < 30: return # image is less than 30 pixels
self.imscale /= self.delta
scale /= self.delta
if event.num == 4 or event.delta == 120: # scroll up
i = min(self.canvas.winfo_width(), self.canvas.winfo_height())
if i < self.imscale: return # 1 pixel is bigger than the visible area
self.imscale *= self.delta
scale *= self.delta
self.canvas.scale('all', x, y, scale, scale) # rescale all canvas objects
self.show_image()
def show_image(self, event=None):
''' Show image on the Canvas '''
bbox1 = self.canvas.bbox(self.container) # get image area
# Remove 1 pixel shift at the sides of the bbox1
bbox1 = (bbox1[0] + 1, bbox1[1] + 1, bbox1[2] - 1, bbox1[3] - 1)
bbox2 = (self.canvas.canvasx(0), # get visible area of the canvas
self.canvas.canvasy(0),
self.canvas.canvasx(self.canvas.winfo_width()),
self.canvas.canvasy(self.canvas.winfo_height()))
bbox = [min(bbox1[0], bbox2[0]), min(bbox1[1], bbox2[1]), # get scroll region box
max(bbox1[2], bbox2[2]), max(bbox1[3], bbox2[3])]
if bbox[0] == bbox2[0] and bbox[2] == bbox2[2]: # whole image in the visible area
bbox[0] = bbox1[0]
bbox[2] = bbox1[2]
if bbox[1] == bbox2[1] and bbox[3] == bbox2[3]: # whole image in the visible area
bbox[1] = bbox1[1]
bbox[3] = bbox1[3]
self.canvas.configure(scrollregion=bbox) # set scroll region
x1 = max(bbox2[0] - bbox1[0], 0) # get coordinates (x1,y1,x2,y2) of the image tile
y1 = max(bbox2[1] - bbox1[1], 0)
x2 = min(bbox2[2], bbox1[2]) - bbox1[0]
y2 = min(bbox2[3], bbox1[3]) - bbox1[1]
if int(x2 - x1) > 0 and int(y2 - y1) > 0: # show image if it in the visible area
x = min(int(x2 / self.imscale), self.width) # sometimes it is larger on 1 pixel...
y = min(int(y2 / self.imscale), self.height) # ...and sometimes not
image = self.image.crop((int(x1 / self.imscale), int(y1 / self.imscale), x, y))
imagetk = ImageTk.PhotoImage(image.resize((int(x2 - x1), int(y2 - y1))))
imageid = self.canvas.create_image(max(bbox2[0], bbox1[0]), max(bbox2[1], bbox1[1]),
anchor='nw', image=imagetk)
self.canvas.lower(imageid) # set image into background
self.canvas.imagetk = imagetk # keep an extra reference to prevent garbage-collection
path = 'doge.jpg' # place path to your image here
root = tk.Tk()
app = Zoom_Advanced(root, path=path)
root.mainloop()
EDIT:
I've created even more advanced zoom. There is "image pyramid" for smooth zooming of large images and even ability to open and zoom huge TIFF files up to several gigabytes.
Version 3.0 is tested on Windows 7 64-bit and Python 3.7.
# -*- coding: utf-8 -*-
# Advanced zoom for images of various types from small to huge up to several GB
import math
import warnings
import tkinter as tk
from tkinter import ttk
from PIL import Image, ImageTk
class AutoScrollbar(ttk.Scrollbar):
""" A scrollbar that hides itself if it's not needed. Works only for grid geometry manager """
def set(self, lo, hi):
if float(lo) <= 0.0 and float(hi) >= 1.0:
self.grid_remove()
else:
self.grid()
ttk.Scrollbar.set(self, lo, hi)
def pack(self, **kw):
raise tk.TclError('Cannot use pack with the widget ' + self.__class__.__name__)
def place(self, **kw):
raise tk.TclError('Cannot use place with the widget ' + self.__class__.__name__)
class CanvasImage:
""" Display and zoom image """
def __init__(self, placeholder, path):
""" Initialize the ImageFrame """
self.imscale = 1.0 # scale for the canvas image zoom, public for outer classes
self.__delta = 1.3 # zoom magnitude
self.__filter = Image.ANTIALIAS # could be: NEAREST, BILINEAR, BICUBIC and ANTIALIAS
self.__previous_state = 0 # previous state of the keyboard
self.path = path # path to the image, should be public for outer classes
# Create ImageFrame in placeholder widget
self.__imframe = ttk.Frame(placeholder) # placeholder of the ImageFrame object
# Vertical and horizontal scrollbars for canvas
hbar = AutoScrollbar(self.__imframe, orient='horizontal')
vbar = AutoScrollbar(self.__imframe, orient='vertical')
hbar.grid(row=1, column=0, sticky='we')
vbar.grid(row=0, column=1, sticky='ns')
# Create canvas and bind it with scrollbars. Public for outer classes
self.canvas = tk.Canvas(self.__imframe, highlightthickness=0,
xscrollcommand=hbar.set, yscrollcommand=vbar.set)
self.canvas.grid(row=0, column=0, sticky='nswe')
self.canvas.update() # wait till canvas is created
hbar.configure(command=self.__scroll_x) # bind scrollbars to the canvas
vbar.configure(command=self.__scroll_y)
# Bind events to the Canvas
self.canvas.bind('<Configure>', lambda event: self.__show_image()) # canvas is resized
self.canvas.bind('<ButtonPress-1>', self.__move_from) # remember canvas position
self.canvas.bind('<B1-Motion>', self.__move_to) # move canvas to the new position
self.canvas.bind('<MouseWheel>', self.__wheel) # zoom for Windows and MacOS, but not Linux
self.canvas.bind('<Button-5>', self.__wheel) # zoom for Linux, wheel scroll down
self.canvas.bind('<Button-4>', self.__wheel) # zoom for Linux, wheel scroll up
# Handle keystrokes in idle mode, because program slows down on a weak computers,
# when too many key stroke events in the same time
self.canvas.bind('<Key>', lambda event: self.canvas.after_idle(self.__keystroke, event))
# Decide if this image huge or not
self.__huge = False # huge or not
self.__huge_size = 14000 # define size of the huge image
self.__band_width = 1024 # width of the tile band
Image.MAX_IMAGE_PIXELS = 1000000000 # suppress DecompressionBombError for the big image
with warnings.catch_warnings(): # suppress DecompressionBombWarning
warnings.simplefilter('ignore')
self.__image = Image.open(self.path) # open image, but down't load it
self.imwidth, self.imheight = self.__image.size # public for outer classes
if self.imwidth * self.imheight > self.__huge_size * self.__huge_size and \
self.__image.tile[0][0] == 'raw': # only raw images could be tiled
self.__huge = True # image is huge
self.__offset = self.__image.tile[0][2] # initial tile offset
self.__tile = [self.__image.tile[0][0], # it have to be 'raw'
[0, 0, self.imwidth, 0], # tile extent (a rectangle)
self.__offset,
self.__image.tile[0][3]] # list of arguments to the decoder
self.__min_side = min(self.imwidth, self.imheight) # get the smaller image side
# Create image pyramid
self.__pyramid = [self.smaller()] if self.__huge else [Image.open(self.path)]
# Set ratio coefficient for image pyramid
self.__ratio = max(self.imwidth, self.imheight) / self.__huge_size if self.__huge else 1.0
self.__curr_img = 0 # current image from the pyramid
self.__scale = self.imscale * self.__ratio # image pyramide scale
self.__reduction = 2 # reduction degree of image pyramid
w, h = self.__pyramid[-1].size
while w > 512 and h > 512: # top pyramid image is around 512 pixels in size
w /= self.__reduction # divide on reduction degree
h /= self.__reduction # divide on reduction degree
self.__pyramid.append(self.__pyramid[-1].resize((int(w), int(h)), self.__filter))
# Put image into container rectangle and use it to set proper coordinates to the image
self.container = self.canvas.create_rectangle((0, 0, self.imwidth, self.imheight), width=0)
self.__show_image() # show image on the canvas
self.canvas.focus_set() # set focus on the canvas
def smaller(self):
""" Resize image proportionally and return smaller image """
w1, h1 = float(self.imwidth), float(self.imheight)
w2, h2 = float(self.__huge_size), float(self.__huge_size)
aspect_ratio1 = w1 / h1
aspect_ratio2 = w2 / h2 # it equals to 1.0
if aspect_ratio1 == aspect_ratio2:
image = Image.new('RGB', (int(w2), int(h2)))
k = h2 / h1 # compression ratio
w = int(w2) # band length
elif aspect_ratio1 > aspect_ratio2:
image = Image.new('RGB', (int(w2), int(w2 / aspect_ratio1)))
k = h2 / w1 # compression ratio
w = int(w2) # band length
else: # aspect_ratio1 < aspect_ration2
image = Image.new('RGB', (int(h2 * aspect_ratio1), int(h2)))
k = h2 / h1 # compression ratio
w = int(h2 * aspect_ratio1) # band length
i, j, n = 0, 1, round(0.5 + self.imheight / self.__band_width)
while i < self.imheight:
print('\rOpening image: {j} from {n}'.format(j=j, n=n), end='')
band = min(self.__band_width, self.imheight - i) # width of the tile band
self.__tile[1][3] = band # set band width
self.__tile[2] = self.__offset + self.imwidth * i * 3 # tile offset (3 bytes per pixel)
self.__image.close()
self.__image = Image.open(self.path) # reopen / reset image
self.__image.size = (self.imwidth, band) # set size of the tile band
self.__image.tile = [self.__tile] # set tile
cropped = self.__image.crop((0, 0, self.imwidth, band)) # crop tile band
image.paste(cropped.resize((w, int(band * k)+1), self.__filter), (0, int(i * k)))
i += band
j += 1
print('\r' + 30*' ' + '\r', end='') # hide printed string
return image
def redraw_figures(self):
""" Dummy function to redraw figures in the children classes """
pass
def grid(self, **kw):
""" Put CanvasImage widget on the parent widget """
self.__imframe.grid(**kw) # place CanvasImage widget on the grid
self.__imframe.grid(sticky='nswe') # make frame container sticky
self.__imframe.rowconfigure(0, weight=1) # make canvas expandable
self.__imframe.columnconfigure(0, weight=1)
def pack(self, **kw):
""" Exception: cannot use pack with this widget """
raise Exception('Cannot use pack with the widget ' + self.__class__.__name__)
def place(self, **kw):
""" Exception: cannot use place with this widget """
raise Exception('Cannot use place with the widget ' + self.__class__.__name__)
# noinspection PyUnusedLocal
def __scroll_x(self, *args, **kwargs):
""" Scroll canvas horizontally and redraw the image """
self.canvas.xview(*args) # scroll horizontally
self.__show_image() # redraw the image
# noinspection PyUnusedLocal
def __scroll_y(self, *args, **kwargs):
""" Scroll canvas vertically and redraw the image """
self.canvas.yview(*args) # scroll vertically
self.__show_image() # redraw the image
def __show_image(self):
""" Show image on the Canvas. Implements correct image zoom almost like in Google Maps """
box_image = self.canvas.coords(self.container) # get image area
box_canvas = (self.canvas.canvasx(0), # get visible area of the canvas
self.canvas.canvasy(0),
self.canvas.canvasx(self.canvas.winfo_width()),
self.canvas.canvasy(self.canvas.winfo_height()))
box_img_int = tuple(map(int, box_image)) # convert to integer or it will not work properly
# Get scroll region box
box_scroll = [min(box_img_int[0], box_canvas[0]), min(box_img_int[1], box_canvas[1]),
max(box_img_int[2], box_canvas[2]), max(box_img_int[3], box_canvas[3])]
# Horizontal part of the image is in the visible area
if box_scroll[0] == box_canvas[0] and box_scroll[2] == box_canvas[2]:
box_scroll[0] = box_img_int[0]
box_scroll[2] = box_img_int[2]
# Vertical part of the image is in the visible area
if box_scroll[1] == box_canvas[1] and box_scroll[3] == box_canvas[3]:
box_scroll[1] = box_img_int[1]
box_scroll[3] = box_img_int[3]
# Convert scroll region to tuple and to integer
self.canvas.configure(scrollregion=tuple(map(int, box_scroll))) # set scroll region
x1 = max(box_canvas[0] - box_image[0], 0) # get coordinates (x1,y1,x2,y2) of the image tile
y1 = max(box_canvas[1] - box_image[1], 0)
x2 = min(box_canvas[2], box_image[2]) - box_image[0]
y2 = min(box_canvas[3], box_image[3]) - box_image[1]
if int(x2 - x1) > 0 and int(y2 - y1) > 0: # show image if it in the visible area
if self.__huge and self.__curr_img < 0: # show huge image
h = int((y2 - y1) / self.imscale) # height of the tile band
self.__tile[1][3] = h # set the tile band height
self.__tile[2] = self.__offset + self.imwidth * int(y1 / self.imscale) * 3
self.__image.close()
self.__image = Image.open(self.path) # reopen / reset image
self.__image.size = (self.imwidth, h) # set size of the tile band
self.__image.tile = [self.__tile]
image = self.__image.crop((int(x1 / self.imscale), 0, int(x2 / self.imscale), h))
else: # show normal image
image = self.__pyramid[max(0, self.__curr_img)].crop( # crop current img from pyramid
(int(x1 / self.__scale), int(y1 / self.__scale),
int(x2 / self.__scale), int(y2 / self.__scale)))
#
imagetk = ImageTk.PhotoImage(image.resize((int(x2 - x1), int(y2 - y1)), self.__filter))
imageid = self.canvas.create_image(max(box_canvas[0], box_img_int[0]),
max(box_canvas[1], box_img_int[1]),
anchor='nw', image=imagetk)
self.canvas.lower(imageid) # set image into background
self.canvas.imagetk = imagetk # keep an extra reference to prevent garbage-collection
def __move_from(self, event):
""" Remember previous coordinates for scrolling with the mouse """
self.canvas.scan_mark(event.x, event.y)
def __move_to(self, event):
""" Drag (move) canvas to the new position """
self.canvas.scan_dragto(event.x, event.y, gain=1)
self.__show_image() # zoom tile and show it on the canvas
def outside(self, x, y):
""" Checks if the point (x,y) is outside the image area """
bbox = self.canvas.coords(self.container) # get image area
if bbox[0] < x < bbox[2] and bbox[1] < y < bbox[3]:
return False # point (x,y) is inside the image area
else:
return True # point (x,y) is outside the image area
def __wheel(self, event):
""" Zoom with mouse wheel """
x = self.canvas.canvasx(event.x) # get coordinates of the event on the canvas
y = self.canvas.canvasy(event.y)
if self.outside(x, y): return # zoom only inside image area
scale = 1.0
# Respond to Linux (event.num) or Windows (event.delta) wheel event
if event.num == 5 or event.delta == -120: # scroll down, smaller
if round(self.__min_side * self.imscale) < 30: return # image is less than 30 pixels
self.imscale /= self.__delta
scale /= self.__delta
if event.num == 4 or event.delta == 120: # scroll up, bigger
i = min(self.canvas.winfo_width(), self.canvas.winfo_height()) >> 1
if i < self.imscale: return # 1 pixel is bigger than the visible area
self.imscale *= self.__delta
scale *= self.__delta
# Take appropriate image from the pyramid
k = self.imscale * self.__ratio # temporary coefficient
self.__curr_img = min((-1) * int(math.log(k, self.__reduction)), len(self.__pyramid) - 1)
self.__scale = k * math.pow(self.__reduction, max(0, self.__curr_img))
#
self.canvas.scale('all', x, y, scale, scale) # rescale all objects
# Redraw some figures before showing image on the screen
self.redraw_figures() # method for child classes
self.__show_image()
def __keystroke(self, event):
""" Scrolling with the keyboard.
Independent from the language of the keyboard, CapsLock, <Ctrl>+<key>, etc. """
if event.state - self.__previous_state == 4: # means that the Control key is pressed
pass # do nothing if Control key is pressed
else:
self.__previous_state = event.state # remember the last keystroke state
# Up, Down, Left, Right keystrokes
if event.keycode in [68, 39, 102]: # scroll right: keys 'D', 'Right' or 'Numpad-6'
self.__scroll_x('scroll', 1, 'unit', event=event)
elif event.keycode in [65, 37, 100]: # scroll left: keys 'A', 'Left' or 'Numpad-4'
self.__scroll_x('scroll', -1, 'unit', event=event)
elif event.keycode in [87, 38, 104]: # scroll up: keys 'W', 'Up' or 'Numpad-8'
self.__scroll_y('scroll', -1, 'unit', event=event)
elif event.keycode in [83, 40, 98]: # scroll down: keys 'S', 'Down' or 'Numpad-2'
self.__scroll_y('scroll', 1, 'unit', event=event)
def crop(self, bbox):
""" Crop rectangle from the image and return it """
if self.__huge: # image is huge and not totally in RAM
band = bbox[3] - bbox[1] # width of the tile band
self.__tile[1][3] = band # set the tile height
self.__tile[2] = self.__offset + self.imwidth * bbox[1] * 3 # set offset of the band
self.__image.close()
self.__image = Image.open(self.path) # reopen / reset image
self.__image.size = (self.imwidth, band) # set size of the tile band
self.__image.tile = [self.__tile]
return self.__image.crop((bbox[0], 0, bbox[2], band))
else: # image is totally in RAM
return self.__pyramid[0].crop(bbox)
def destroy(self):
""" ImageFrame destructor """
self.__image.close()
map(lambda i: i.close, self.__pyramid) # close all pyramid images
del self.__pyramid[:] # delete pyramid list
del self.__pyramid # delete pyramid variable
self.canvas.destroy()
self.__imframe.destroy()
class MainWindow(ttk.Frame):
""" Main window class """
def __init__(self, mainframe, path):
""" Initialize the main Frame """
ttk.Frame.__init__(self, master=mainframe)
self.master.title('Advanced Zoom v3.0')
self.master.geometry('800x600') # size of the main window
self.master.rowconfigure(0, weight=1) # make the CanvasImage widget expandable
self.master.columnconfigure(0, weight=1)
canvas = CanvasImage(self.master, path) # create widget
canvas.grid(row=0, column=0) # show widget
filename = './data/img_plg5.png' # place path to your image here
#filename = 'd:/Data/yandex_z18_1-1.tif' # huge TIFF file 1.4 GB
#filename = 'd:/Data/The_Garden_of_Earthly_Delights_by_Bosch_High_Resolution.jpg'
#filename = 'd:/Data/The_Garden_of_Earthly_Delights_by_Bosch_High_Resolution.tif'
#filename = 'd:/Data/heic1502a.tif'
#filename = 'd:/Data/land_shallow_topo_east.tif'
#filename = 'd:/Data/X1D5_B0002594.3FR'
app = MainWindow(tk.Tk(), path=filename)
app.mainloop()
Adding Zooming in and out with a Tkinter Canvas Widget?
To my knowledge the built-in Tkinter Canvas class scale will not auto-scale images. If you are unable to use a custom widget, you can scale the raw image and replace it on the canvas when the scale function is invoked.
The code snippet below can be merged into your original class. It does the following:
- Caches the result of
Image.open(). - Adds a
redraw()function to calculate the scaled image and adds that to the canvas, and also removes the previously-drawn image if any. - Uses the mouse coordinates as part of the image placement. I just pass
x and yto thecreate_imagefunction to show how the image placement shifts around as the mouse moves. You can replace this with your own center/offset calculation. - This uses the Linux mousewheel buttons 4 and 5 (you'll need to generalize it to work on Windows, etc).
(Updated) Code:
class GUI:
def __init__(self, root):
# ... omitted rest of initialization code
self.canvas.config(scrollregion=self.canvas.bbox(ALL))
self.scale = 1.0
self.orig_img = Image.open(File)
self.img = None
self.img_id = None
# draw the initial image at 1x scale
self.redraw()
# ... rest of init, bind buttons, pack frame
def zoom(self,event):
if event.num == 4:
self.scale *= 2
elif event.num == 5:
self.scale *= 0.5
self.redraw(event.x, event.y)
def redraw(self, x=0, y=0):
if self.img_id:
self.canvas.delete(self.img_id)
iw, ih = self.orig_img.size
size = int(iw * self.scale), int(ih * self.scale)
self.img = ImageTk.PhotoImage(self.orig_img.resize(size))
self.img_id = self.canvas.create_image(x, y, image=self.img)
# tell the canvas to scale up/down the vector objects as well
self.canvas.scale(ALL, x, y, self.scale, self.scale)
Update I did a bit of testing for varying scales and found that quite a bit of memory is being used by resize / create_image. I ran the test using a 540x375 JPEG on a Mac Pro with 32GB RAM. Here is the memory used for different scale factors:
1x (500, 375) 14 M
2x (1000, 750) 19 M
4x (2000, 1500) 42 M
8x (4000, 3000) 181 M
16x (8000, 6000) 640 M
32x (16000, 12000) 1606 M
64x (32000, 24000) ...
reached around ~7400 M and ran out of memory, EXC_BAD_ACCESS in _memcpy
Given the above, a more efficient solution might be to determine the size of the viewport where the image will be displayed, calculate a cropping rectangle around the center of the mouse coordinates, crop the image using the rect, then scale just the cropped portion. This should use constant memory for storing the temporary image. Otherwise you may need to use a 3rd party Tkinter control which performs this cropping / windowed scaling for you.
Update 2 Working but oversimplified cropping logic, just to get you started:
def redraw(self, x=0, y=0):
if self.img_id: self.canvas.delete(self.img_id)
iw, ih = self.orig_img.size
# calculate crop rect
cw, ch = iw / self.scale, ih / self.scale
if cw > iw or ch > ih:
cw = iw
ch = ih
# crop it
_x = int(iw/2 - cw/2)
_y = int(ih/2 - ch/2)
tmp = self.orig_img.crop((_x, _y, _x + int(cw), _y + int(ch)))
size = int(cw * self.scale), int(ch * self.scale)
# draw
self.img = ImageTk.PhotoImage(tmp.resize(size))
self.img_id = self.canvas.create_image(x, y, image=self.img)
gc.collect()
Move and zoom a tkinter canvas with mouse
Mouse events are reported in 'screen coordinates'. When you have a scrolled
canvas, you often need to convert those numbers to 'canvas (ie. scrollregion)
coordinates'.
eg. for your zoom focus:
true_x = canvas.canvasx(event.x)
true_y = canvas.canvasy(event.y)
When I scan_dragto to pan my canvas, all canvas items move properly but their coordinates don't change
Initially the origin (0, 0) of the canvas is at top-left corner of the view port , therefore event.x
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