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 randomimport tkinter as tkfrom tkinter import ttkfrom PIL import Image, ImageTkclass 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-collectionpath = 'doge.jpg' # place path to your image hereroot = 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 GBimport mathimport warningsimport tkinter as tkfrom tkinter import ttkfrom PIL import Image, ImageTkclass 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 widgetfilename = './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.
(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, EventTypecanvas.bind("<MouseWheel>", do_zoom)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)
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.