Tkinter canvas zoom + move/pan

Question

Tkinter's canvas widget has built-in features to:

• move/pan the canvas (for example with Click + Drag) with canvas.scan_mark and canvas.scan_dragto, see this question

• zoom the vector elements on the canvas with canvas.scale, but sadly, this doesn't work for bitmap images on the canvas

Fortunately, this method allows zooming of images (by manually redrawing the zoomed portion of the image). But:

1. As we are redrawing a particular portion of the canvas, move/pan feature won't work anymore...

2. We absolutely need to render more than the currently displayed area, to allow move/pan. Let's say we have 1000x1000 bitmap on the canvas, and we want to zoom by a factor 50x... How to avoid having a 50.000 x 50.000 pixels bitmap in memory? (2.5 gigapixels in RAM is too big). We could think about rendering the viewport only, or a bit more than the current viewport to allow panning, but then what to do once panning leads to the edge of the rendered zone?

How to have a move/pan + zoom feature on Tkinter canvas, that works for images?

Defecate

Have you considered using PyQt over TkInter? It has a much better abstraction separating the view (the UI part, where you zoom, scroll and rotate) and the actual scene: doc.qt.io/qt-5/graphicsview.html#zooming-and-rotating You can just throw your graphics elements onto the scene once and then basically forget about them, if you so desire, as they don't need to be changed for panning and zooming to work. – Erne

@Erne I have already coded all the rest of the UI in Tkinter, so if possible I would like to keep Tkinter. If not, I would probably move to wxPython (so a solution in wxPython would be interesting as well) which I already know. – Defecate

@user650881 Any idea about how to do this using tiles? – Defecate

@Defecate perhaps something like in this book example – Forename

Be aware that the scrollregion should be bigger than the canvas – Juryrig

Answer 1

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()

P.S. Here is the GitHub application using advanced zoom for manual image annotation with polygons.

Repletion

It's awesome! This code displays the zoomed upper left corner of image. Is it possible to display the centered image at the original size at first? – Sinistrality

@Sinistrality Yes, it is possible to generate an event in initialization function __init__. In this event you should call functions move_from and move_to to move canvas self.canvas to the new position, i.e. to the center of the canvas. These are the same events when dragging image with the mouse. Something like event_generate: https://mcmap.net/q/152024/-tkinter-invoke-event-in-main-loop Unfortunately, I cannot remember more for now. – Repletion

Nice - unfortunately it does not work with the touchpad of a Mac (well, drag-panning works, but two finger pinch/pan do not) – Centrality

@Centrality add or event.delta < 0 and or event.delta > 0 to lines 230 and 234 respectively. MacOS's scroll deltas are different from Windows and Linux – Deemphasize

Answer 2

(The question TITLE doesn't indicate that it's focused on bitmaps. I add an answer here for those who were interested in basic zoom/pan support for canvas, and got here by a search engine)

The fundamental mechanism to support zoom (with wheel) and move/pan (with left-button drag) is as follows:

from tkinter import ALL, EventType

canvas.bind("<MouseWheel>", do_zoom) # WINDOWS ONLY
canvas.bind('<ButtonPress-1>', lambda event: canvas.scan_mark(event.x, event.y))
canvas.bind("<B1-Motion>", lambda event: canvas.scan_dragto(event.x, event.y, gain=1))

def do_zoom(event):
    x = canvas.canvasx(event.x)
    y = canvas.canvasy(event.y)
    factor = 1.001 ** event.delta
    canvas.scale(ALL, x, y, factor, factor)

Simple extension: support zooming of each axis individually, by looking at the state of Ctrl and Shift, as follows:

def do_zoom(event):
    x = canvas.canvasx(event.x)
    y = canvas.canvasy(event.y)
    factor = 1.001 ** event.delta
    is_shift = event.state & (1 << 0) != 0
    is_ctrl = event.state & (1 << 2) != 0
    canvas.scale(ALL, x, y, 
                 factor if not is_shift else 1.0, 
                 factor if not is_ctrl else 1.0)

MORE MOUSE WHEEL EVENTS: Linux mice generate <4> and <5> (Zoom plus, zoom minus, respectively). Additional event handlers are necessary as follows. Note that this example is pedantic; obviously the Zoom In and Zoom Out handlers could be collapsed into one handler with some math and a lambda.

def do_zoom_in(event):
  x = canvas.canvasx(event.x)
  y = canvas.canvasy(event.y)
  factor = 1.1
  canvas.scale(ALL, x, y, factor, factor)

def do_zoom_out(event):
  x = canvas.canvasx(event.x)
  y = canvas.canvasy(event.y)
  factor = 0.9
  canvas.scale(ALL, x, y, factor, factor)

canvas.bind('<4>', do_zoom_in)
canvas.bind('<5>', do_zoom_out) 

Gloxinia

Answer 3

You might consider using map tiles for this case. The tiles can be specific to the zoom level. After selecting the tiles based on the pan and zoom level you can position them on the canvas with Canvas.create_image.

Assuming you have some tile class with its coordinates and image, you could select for visible tiles based on the pan, zoom and frame size.

for tile in visible_tiles(pan_center, frame_dimensions, zoom_level):
    canvas.create_image(tile.x, tile.y, anchor=Tkinter.NW, image=tile.image)

There is a full sample of this in Tile-Based Geospatial Information Systems by John Sample and Elias Ioup in the chapter on Tiled Mapping Clients.

Forename

Looks interesting, but this source is quite expensive (109$). Could you insert a minimal code example of how to do it in Python? – Defecate

I linked to an online excerpt from the book in my previous comment response. – Forename

Answer 4

The provided answer is really good and works on really large images as well. However, if you want a zoom/pan that zooms on mouse point as well as keeps the image in the frame see attached code. You can adjust the self.zoom_cycle in the function def mouse_wheel(self, event) to make the zoom go as far out or far in as you want. Also you need to adjust the max_y = scale * 3072 and max_x = scale * 4096 to use the constants for the width/height of the image you want to display. *Note this allows you to use full size image resolution in an arbitrary frame size. Just make sure that you set the canvas_w and canvas_h to the same ratio as the image you are trying to display.

import tkinter as tk             
from PIL import Image, ImageTk  
import numpy as np                                

class PanZoomCanvas(tk.Frame):
    def __init__(self, master,canvas_w,canvas_h):
        super().__init__(master)
        self.pil_image = None   # Image data to be displayed

        self.zoom_cycle = 0

        self.create_widget(canvas_w,canvas_h) # Create canvas
        
        # Initial affine transformation matrix
        self.reset_transform()
 
    # Define the create_widget method.
    def create_widget(self,width,height):
        # Canvas
        self.canvas = tk.Canvas(self.master, background="black", width = width,height = height)
        self.canvas.pack() 

        # Controls
        self.master.bind("<Button-1>", self.mouse_down_left)                   # MouseDown
        self.master.bind("<B1-Motion>", self.mouse_move_left)                  # MouseDrag
        self.master.bind("<Double-Button-1>", self.mouse_double_click_left)    # MouseDoubleClick
        self.master.bind("<MouseWheel>", self.mouse_wheel)                     # MouseWheel


    def set_image(self, filename):
        '''To open an image file'''
        if not filename:
            return
        # PIL.Image
        self.pil_image = Image.open(filename)
        # Set the affine transformation matrix to display the entire image.
        self.zoom_fit(self.pil_image.width, self.pil_image.height)
        # To display the image
        self.draw_image(self.pil_image)

    # -------------------------------------------------------------------------------
    # Mouse events
    # -------------------------------------------------------------------------------
    def mouse_down_left(self, event):
        self.__old_event = event

    def mouse_move_left(self, event):
        if (self.pil_image == None):
            return
        
        self.translate(event.x - self.__old_event.x, event.y - self.__old_event.y)
        self.redraw_image()
        self.__old_event = event



    def mouse_double_click_left(self, event):
        if self.pil_image == None:
            return
        self.zoom_fit(self.pil_image.width, self.pil_image.height)
        self.redraw_image() 

    def mouse_wheel(self, event):
        if self.pil_image == None:
            return

        if (event.delta < 0):
            if self.zoom_cycle <= 0:
                return
            # Rotate upwards and shrink
            self.scale_at(0.8, event.x, event.y)
            self.zoom_cycle -= 1
        else:
            if self.zoom_cycle >= 9:
                return
            #  Rotate downwards and enlarge
            self.scale_at(1.25, event.x, event.y)
            self.zoom_cycle += 1
    
        self.redraw_image() # Refresh
        
    # -------------------------------------------------------------------------------
    # Affine Transformation for Image Display
    # -------------------------------------------------------------------------------

    def reset_transform(self):
        self.mat_affine = np.eye(3) # 3x3の単位行列

    def translate(self, offset_x, offset_y,zoom = False):
        mat = np.eye(3) # 3x3 identity matrix
        mat[0, 2] = float(offset_x)
        mat[1, 2] = float(offset_y)
        # Get the current canvas size
        canvas_width = self.canvas.winfo_width()
        canvas_height = self.canvas.winfo_height()
        
        # Get the current scale
        scale = self.mat_affine[0, 0]
        max_y = scale * 3072
        max_x = scale * 4096
        self.mat_affine = np.dot(mat, self.mat_affine)

        if not zoom:
            if abs(self.mat_affine[0,2]) > abs(max_x-canvas_width):
                self.mat_affine[0,2] = -(max_x-canvas_width)
            if abs(self.mat_affine[1,2]) > abs(max_y-canvas_height):
                self.mat_affine[1,2] = -(max_y-canvas_height)

        if self.mat_affine[0, 2] > 0.0:
            self.mat_affine[0, 2] = 0.0
        if self.mat_affine[1,2] > 0.0:
            self.mat_affine[1,2]  = 0.0

    def scale(self, scale:float):
        mat = np.eye(3) # 3x3 identity matrix

        mat[0, 0] = scale
        mat[1, 1] = scale
        self.mat_affine = np.dot(mat, self.mat_affine)

    def scale_at(self, scale:float, cx:float, cy:float):

        # Translate to the origin
        self.translate(-cx, -cy, True)
        # Scale
        self.scale(scale)
        # Restore
        self.translate(cx, cy)

    def zoom_fit(self, image_width, image_height):

        # Update canvas object and get size
        self.master.update()
        canvas_width = self.canvas.winfo_width()
        canvas_height = self.canvas.winfo_height()

        if (image_width * image_height <= 0) or (canvas_width * canvas_height <= 0):
            return

        # Initialization of affine transformation
        self.reset_transform()

        scale = 1.0
        offsetx = 0.0
        offsety = 0.0
        if (canvas_width * image_height) > (image_width * canvas_height):
            # The widget is horizontally elongated (resizing the image vertically)
            scale = canvas_height / image_height
            # Align the remaining space to the center by offsetting horizontally
            offsetx = (canvas_width - image_width * scale) / 2
        else:
            # The widget is vertically elongated (resizing the image horizontally)
            scale = canvas_width / image_width
            # Align the remaining space to the center by offsetting vertically
            offsety = (canvas_height - image_height * scale) / 2

        # Scale
        self.scale(scale)
        # Align the remaining space to the center
        self.translate(offsetx, offsety)
        self.zoom_cycle = 0

    def to_image_point(self, x, y):
        '''Convert coordinates from the canvas to the image'''
        if self.pil_image == None:
            return []
        # Convert coordinates from the image to the canvas by taking the inverse of the transformation matrix.
        mat_inv = np.linalg.inv(self.mat_affine)
        image_point = np.dot(mat_inv, (x, y, 1.))
        if  image_point[0] < 0 or image_point[1] < 0 or image_point[0] > self.pil_image.width or image_point[1] > self.pil_image.height:
            return []

        return image_point

    # -------------------------------------------------------------------------------
    # Drawing 
    # -------------------------------------------------------------------------------

    def draw_image(self, pil_image):
        
        if pil_image == None:
            return

        self.pil_image = pil_image

        # Canvas size
        canvas_width = self.canvas.winfo_width()
        canvas_height = self.canvas.winfo_height()

        # Calculate the affine transformation matrix from canvas to image data
        # (Calculate the inverse of the display affine transformation matrix)
        mat_inv = np.linalg.inv(self.mat_affine)

        # Convert the numpy array to a tuple for affine transformation
        affine_inv = (
            mat_inv[0, 0], mat_inv[0, 1], mat_inv[0, 2],
            mat_inv[1, 0], mat_inv[1, 1], mat_inv[1, 2]
        )

        # Apply affine transformation to the PIL image data
        dst = self.pil_image.transform(
            (canvas_width, canvas_height),  # Output size
            Image.AFFINE,   # Affine transformation
            affine_inv,     # Affine transformation matrix (conversion matrix from output to input)
            Image.NEAREST   # Interpolation method, nearest neighbor
        )

        im = ImageTk.PhotoImage(image=dst)

        # Draw the image
        item = self.canvas.create_image(
            0, 0,           # Image display position (top-left coordinate)
            anchor='nw',    # Anchor, top-left is the origin
            image=im        # Display image data
        )
        self.image = im

    def redraw_image(self):
        '''Redraw the image'''
        if self.pil_image == None:
            return
        self.draw_image(self.pil_image)


if __name__ == "__main__":
    root = tk.Tk()
    root.geometry('1200x900')
    app = PanZoomCanvas(master=root,canvas_w = 1024,canvas_h = 768)
    app.canvas.config(bg = 'grey')
    app.set_image('image_path_here')
    app.mainloop()

Courbet