Develop Reference

How can I make a tkinter canvas hold an image much greater than the available screen size?

I'm attempting to adapt martineau's excellent answer on how to use tkinter to highlight and select an area of an image with a mouse. My goal is to modify the code to support huge images, such as 10000x6000 pixels or more!
This is my first attempt at using tkinter, and it's much more challenging than expected.
The three options which I've considered and experimented with are:
Load the image, then scale the image to the size available in the window before placing it on the canvas. This in turn requires that I know the scale factor, so I can reverse the scaling when operating on the original image.
Add scrollbars to the side/button on the visible part of the image in the canvas. (My preferred option).
Don't add scrollbars, but use the cursor keys to scroll the visible part of the image in the canvas.
I've tried to do all of them, but ran into various kinds of trouble:
I used root.state('zoomed') to maximize the window, then placed a button to top of the window using tk.Button(...).pack(fill=tk.X) before placing the canvas as in the linked code using self.canvas = tk.Canvas(...). At this time I discovered two issues: It turns out that I can't maximize the canvas to the remaining space in the window using self.canvas.pack(fill=tk.BOTH) (it only expands the width). Another more crucial issue was that I could not read the actual width/height value that the canvas was expanded to, (or get there available space in the window before placing the canvas), and without these values, I can't calculate the scaling factor. :-(
I tried to follow various methods of adding scrollbars to the packed canvas but they all, with one exception, required to use the grid method and I quickly found that pack and grid methods were conflicting methods. After several attempts at rewriting the code to use the grid method, I gave up. The place method seemed promising, except that it will require me to size the canvas manually and then place the scrollbars at calculated offsets to the canvas... and all of this required that I have the same values that were needed to calculate the scaling factor above. :-(
I didn't get very far with this, as it seems I can't get (keyboard?) binds to work at all (On windows with Python 3.10.6). Shouldn't something like self.canvas.bind("<Right>", lambda event: print("Ping")) followed by self.canvas.focus_set() (perhaps with root instead of the canvas) work?
I'm sure I'm overlooking something basic, but after a few evenings looking at this I've gotten nowhere. :-(
I hope some of you can provide help and/or pointers allowing me to get further.
Ohh, for completeness, I'm trying to hack together a small tool that does the following:
On startup requests and load an image file. (Adding a button to perform the load/re-load is nice to have, but not strictly needed. )
Display the image file and allow an area of the image to be selected with the mouse.
Perform some software analysis on the selected part of the image when a button is pressed.

Tkinter screwing with PIL image transparency?

I made a custom image viewing program in python since I couldn't find one that worked how I wanted it to, and I know it at least USED to work with transparent gifs but now it doesn't. The effects seem to vary from gif to gif to gif but it always is an issue with the transparency. Doing some testing with .save I found that the PIL image is completely fine and I can export it as a png with absolutely no issues and perfect transparency. With that said, despite making the program I never really learned Tkinter since I just didn't need to use it beyond simple canvas clearing and updating, so I have no clue how to test beyond PIL. I believe the issue should be in these lines :
image = ImageTk.PhotoImage(GifFrameSized) #GifFrameSized is the resized GIF
imagesprite = canvas.create_image(show.w/2,show.h/2,image=image) #w and h are the width and height of the monitor
root.update_idletasks()
root.update()
canvas.pack()
I genuinely have no idea how the issue could be coming from any of these but I was able to use PIL to save a png of the frame in the line immediately above "image = ImageTk.PhotoImage(GifFrameSized)" and it looked fine so I have to imagine its somewhere in those lines.

Tkinter default font is tiny

I am using some libraries that are using tkinter, and the font is so tiny I can't read it (a few pixels only). Here is a minimum working example:
from tkinter import *
root = Tk()
myLabel = Label(root, text = 'Hello, world!')
myLabel.pack()
root.mainloop()
The working example produces the tiny hello world in the window to the right: mwe tiny font
The rest of the image is showing the gitk gui as a size reference.
Is there a way to set the default font size in tkinter without changing the code? It could also be a problem with dpi settings?
I am on Arch linux, i3wm, using the nvidia proprietary driver

Add this line to the beginning of your code. change helevicta by the font you want to use, change 20 by the font size you want to use and change bold by any formatting options you want (you don't have to include any, and if you do, you can add more than one.) This line will set the font for any labels in the root window.
root.option_add("*Label.Font", "helvetica 20 bold")

I found a workaround to my problem.
Tkinter has an automatic way to determine the monitor size and it will set a tk scale variable accordingly. In my case the scaling value does the opposite of what it is supposed to do - larger scaling value leads to smaller font size. I still don't know why that is the case.
I ran strace on my minimum working example and found out that tkinter tries to read the file ~/.Tk.tcl and I can therefore use this file as a configuration file.
Putting tk scaling 1.0 into ~/.Tk.tcl solved the problem for me. You can experiment with the scaling value to increase/decrease the overall scaling of the gui components.
Looking at strace it also tries to read ~/.Tk.py, ~/.example.tcl and ~/.example.py.

Yes you can set default font for tkinter widgets. Refer to this thread
https://stackoverflow.com/questions/15462647/modify-the-default-font-in-python-tkinter#:~:text=2%20Answers&text=Tkinter%20has%20several%20built%2Din,them%20will%20change%20as%20well.

Fastest way to draw a pixel on tkinter

Note: You really only need to read the checklist and understand that I want to do this in Tkinter, the rest of the information is for clarification
The complete code is here: https://gist.github.com/SnugBug/1cc5ea67d11487d69aae8549107372ef
I need to be able to manipulate pixels. The goal is to be able to:
Control which pixels are drawn first
Change the color and position of each pixel
Update everything as a whole, so that if a pixel changes the change shows up
Clear everything as a whole
The question is, what's the fastest way to check off this list in tkinter? I tried creating an image with PIL, then loading it into tkinter, but I cannot update the image or clear it. The other thing I tried is using tkinter's PhotoImage class, as shown below:
#The function definitions are in the GIST.
#This snippet should be enough information to understand the problem, however.
for i in range(0,3600):
rot = [0,i,0]
Tx,Ty,Tz,Zm = [0,0,200,200]
x,y,z = [10,10,10]
for m,n in itertools.product(range(-50,50,2),range(-50,50,2)):
x,y,z = rotate([m,n,0],rot)
img.put("#ffffff", (int(WIDTH/2 + ((x+Tx)*Zm/(z+Tz))), int(HEIGHT/2 - ((y+Ty)*Zm/(z+Tz)))))
canvas.update()
img.blank()
#the confusing math in the `img.put` call is just 3D math
This way is extremely slow. The next way I tried is even slower. It's drawing a line like this:
canvas.create_line(x,y,x+1,y+1, ...)
Which creates a line of length 1, showing a single pixel. This is excruciatingly slow.
If the separate image method is the fastest, could you include a working snippet in your answer? I cannot figure out the separate image method. I have PIL installed, that's what I was using to attempt it. I lost the python file so I cannot include the code I used to attempt the separate image method.
What I mean by the separate image method: create an image using PIL, drawing on it using PIL, then making that show up on a tkinter screen. This doesn't meet everything on the checklist, however (from what I understand).
If the separate image method is not the fastest, please tell me a way I can check off everything in the checklist some other way. I have a few questions I looked at for help and some sites. They're below
Why is Photoimage put slow?
Any of these answers don't work for me because it only creates squares. I need to be able to make any shape.
python tkinter: how to work with pixels?
This answer doesn't work because it's too slow.
How to load .bmp file into BitmapImage class Tkinter python This could be helpful
http://zetcode.com/gui/tkinter/drawing/ None of these methods work because I cannot manipulate the order each pixel is drawn, and the color of each individual pixel. If you are familiar with 3D terminology, I need this for a Z-Buffer
If there are any confusions or you need something clarified, please tell me below in the comment section. I am open minded, so if you have a deep understanding of my question and have another idea on how to solve it, I would love to hear it.

If you are using Windows, then the fastest way to put an image on a frame is by ImageWin. The tkinter process of first transforming from PIL image to a tkphotoimage is very slow.
from PIL import Image, ImageWin
from win32gui import GetDC
from tkinter import Tk
root = Tk()
im = Image.open(<file path>)
ImageWin.Dib(im).draw(
GetDC(ImageWin.HWND(root.winfo_id())),
(0,0,100,100)
)

python tkinter canvas 'transparent'

I think transparent is the right word I'm looking for. Hopefully my description will explain it properly no matter what.
I have a graph of time based data going back decades. Pretty much simply setup to show one day per x-pixel, unless zoomed in closer. I would like to have a box, maybe along the lines of 5x100, appear on top of the graph so when I move the mouse over the graph the box will move and keep pace with the mouse. Anotherwords showing what was happening in the 5 furthest days 'x number of days prior'. Anotherwords when computing an average going forward what are the next values to be falling off as new data arrives. Naturally I want the underlying graphed data to be displayed with the transparent box on top of it outlining the days in question. This may get crazy enough to be a much wider box with two areas that are colored light grey or something like that to show the areas in question but the colored areas are separated by numerous days(could be multiple transparent windows that are tracked together as well. Is this feasible with tkinter? From the research I've been doing it's questionable if using
root.attributes('alpha', .30)
would work or not. It doesn't sound like I could do something like as it would end up making the graph transparent to whatever is underneath it.
self.Graph.create_line()
self.Box.attributes('alpha', .30)
If I understand correctly I have to use
attributes
right at the root level versus the individual 'window' level so the above (severely chopped down) code wouldn't work...or would it. I haven't had a chance to try anything out yet to see what happens...that will be later on this evening. Kinda hoping to save myself a little time by asking now and you never know who else may need the help sometime.

If I understand what you're trying to do, it's going to be pretty hard.
Setting window attributes works just fine to make a window transparent. You've got a minor problem in the code—attributes start with a hyphen—but otherwise you've got it right:
self.Box.attributes("-alpha", .30)
However, it sounds like you want that Box to be an embedded part of the graph window, not its own top-level window that can be dragged around by the user, etc. Unfortunately, Tkinter does not have any notion of child windows, and it doesn't expose nearly enough of the native stuff you'd need to fake them by creating an immobile window and manually moving it to track the movements of another window. So, you don't have a window, which means you don't have window transparency.
The obvious thing for Box to be is some kind of widget, like a Frame or Canvas. But widgets don't have transparency.
Box could instead be just a collection of elements drawn onto the same Canvas as the Graph. That seems promising… but none of the Canvas methods handle alpha transparency. (Some of them do handle all-or-nothing transparency, but that doesn't help.)
One thing that does handle transparency is PhotoImage. So, if you draw Box off-screen, get the resulting contents as a PhotoImage, add the alpha (e.g., via PIL), then create_image the result… close, but no cigar. Depending on the settings of the underlying Tk library, Tkinter may just draw the pixmap with 1-bit transparency or ignore transparency completely. (Experiment with loading alpha-transparent PNG files in PIL and drawing them on a Canvas.) So, unless you want an app that looks right on some systems, doesn't draw the Box at all on others, and draws it opaque on others, this is a dead end.
So, what's left? Only manual compositing: Draw the Graph and the Box on separate off-screen windows, get the pixmaps, use PIL to compose them, and create_image the result.
At which point you're probably better off just using something like PIL's ImageDraw or a more powerful library to construct the pixmap in the first place. Or, of course, using a more powerful GUI library than Tk, like Qt or wx.

Maybe this can give you some ideas to play with:
from tkinter import *
root = Tk()
c = Canvas(root, width=640, height=480, bd=0, highlightthickness=0)
c.create_line(0,240,640,240, fill='blue')
c.pack()
#pil image with transparency
try:
from PIL import Image, ImageTk
except ImportError:
pass
else:
pim = Image.new('RGBA', (5,100), (0,255,0,64))
photo = ImageTk.PhotoImage(pim)
c.create_image(200,200, image=photo, anchor='nw')
#blank standard photoimage with red vertical borders
im = PhotoImage(width=7, height=480)
dat = ('red',)*480
im.put(dat, to=(0,0))
im.put(dat, to=(6,0))
box = c.create_image(0, 0, image=im, anchor='nw')
def on_motion(event):
left,top = c.coords(box)
dx = event.x - (left+7)
c.move(box, dx, 0)
c.bind('<Motion>', on_motion)
root.mainloop()